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Lab Management Guidelines V2.0.2021
Laboratory Testing for Thyroid
Disorders
MOL.CS.320.X
v2.0.2021
Introduction
Laboratory testing for thyroid disorders is addressed by this guideline.
Procedures Addressed
The inclusion of any procedure code in this table does not imply that the code is under
management or requires prior authorization. Refer to the specific Health Plan's
procedure code list for management requirements.
Procedure addressed by this guideline Procedure code
TSH receptor antibodies (TRAb) 83519
TSH receptor antibodies (TRAb) 83520
Thyroglobulin 84432
Thyroxine (T4), Total 84436
Thyroxine (T4) requiring elution (e.g. 84437
neonatal thyroxine)
Free Thyroxine (free T4) 84439
Thyroxine Binding Globulin 84442
Thyroid Stimulating Hormone (TSH; 84443
Thyrotropin)
Thyroid Stimulating Immunoglobulins 84445
(TSI)
Thyroid hormone (T3 OR T4) uptake or 84479
thyroid hormone binding ratio (THBR)
Triiodothyronine (T3) 84480
Free Triiodothyronine (free T3) 84481
Reverse T3 84482
Microsomal (Thyroid peroxidase) 86376
antibodies
Thyroglobulin antibody 86800
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What Are Thyroid Diseases
Definition
The two predominant forms of thyroid dysfunction are hypothyroidism and
hyperthyroidism. The clinical manifestations of hypothyroidism or hyperthyroidism are
broad, common and nonspecific.
The American Association for Clinical Chemistry (AACC) describes the functioning and
interaction of the following hormones and binding proteins: 1
Thyroid hormones: thyroxine (T4) and triiodothyronine (T3) and their binding
proteins, thyroglobulin in the thyroid and thyroxine binding globulin (TBG) in the
circulation.
Pituitary hormone: thyroid stimulating hormone (TSH also known as Thyrotropin).
Hypothalamic hormone: thyrotropin releasing hormone (TRH).
The feedback loop controlling the hormones involves both the central nervous system
and the thyroid gland.1
“The body has an elaborate feedback system to control the amount of T4 and T3 in
the blood. When blood levels of the hormones decrease, the hypothalamus
releases thyrotropin-releasing hormone, which in turn causes the pituitary gland to
release thyroid-stimulating hormone (TSH). TSH stimulates the thyroid gland to
produce and secrete T4 (primarily) and T3. When the system is functioning
normally, thyroid production turns on and off to maintain relatively stable levels of
thyroid hormones. Inside the thyroid, most of the T4 is stored bound to a protein
called thyroglobulin. When the need arises, the thyroid gland produces more T4
and/or releases some of what is stored. In the blood, most T4 and T3 are bound to
a protein called thyroxine-binding globulin (TBG) and are relatively inactive. The
small amounts that are unbound, called free T4 or free T3, are the active forms of
the hormone. T4 is converted to T3 in the liver and other tissues. T3 is primarily
responsible for controlling the rate of body functions.”
Hypothyroidism
Overt hypothyroidism affects approximately 0.5% of the population of the United
States.2-4 Subclinical hypothyroidism, which is defined as a normal free thyroxine (free
Thyroid Testing
T4) concentration despite an elevated thyroid stimulating hormone (TSH) concentration
occurs in an estimated 3-5% of the population. 4,5 Individuals with subclinical
hypothyroidism are at enhanced risk for progression to overt hypothyroidism. This is
the basis for clinically monitoring individuals with subclinical hypothyroidism. 4,6
There are several causes of hypothyroidism. 4,7 The most common in the United States
is Hashimoto’s thyroiditis, an autoimmune disease that causes destruction of the
thyroid. Hashimoto’s thyroiditis is associated with autoantibodies which were originally
known as microsomal antibodies and which are now known to be anti-thyroid
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Lab Management Guidelines V2.0.2021 Test Information Introduction The laboratory tests discussed in this guideline play a foundational role in the diagnosis and monitoring of thyroid disease.4,7,8,11-14 Screening for thyroid disease by laboratory methods is useful because the main causes of hypothyroidism and hyperthyroidism in the United States are common, the laboratory tests used for screening are inexpensive, reasonably accurate and precise, and the treatment is generally safe, effective and reasonably priced. Similarly, many of the tests are also useful for monitoring thyroid disease due to their safety and cost effectiveness. Thyroid Stimulating Hormone (TSH, Thyrotropin), CPT 84443 Although there are many laboratory tests to biochemically assess thyroid function and disease, by far the most useful and most frequently ordered is thyroid stimulating hormone (TSH), also known as thyrotropin.7 TSH is useful as the primary screening test and monitoring test for both hypothyroidism and hyperthyroidism, and it is also important in monitoring and risk stratifying thyroid cancer. 12 When screening, a TSH within the reference range, by itself, rules out hyperthyroidism and hypothyroidism in most cases.4,11,15 In addition, the test is used to monitor the effectiveness of thyroid related therapy for both hyperthyroidism and hypothyroidism. These treatments include thyroid hormone replacement, partial or complete thyroidectomy, radioactive iodine, and pharmaceuticals to reduce or increase thyroid hormone production. 4,11-13,15 The test is performed by automated immunoassay and there are many FDA approved laboratory instruments that can measure TSH accurately and precisely. Thyroxine (T4), CPT 84436, 84437, 84439 After TSH, thyroxine is the most common and useful thyroid function test. Thyroxine is sometimes used with TSH as the primary screening and monitoring tests for both hypothyroidism and hyperthyroidism. In addition, like TSH, the test is used commonly to monitor the effectiveness of thyroid related therapies. 4,11-13,15 As a screening test, TSH and thyroxine within the reference range rule out hypothyroidism or hyperthyroidism. In some cases of hyperthyroidism, a T3 within the reference range is also needed to rule out hyperthyroidism.11 Elevated T4 with low TSH generally suggests primary hyperthyroidism and reduced T4 with an elevated TSH indicates Thyroid Testing primary hypothyroidism. These findings are usually accompanied by characteristic symptoms. Secondary hypothyroidism or hyperthyroidism is rare and refers to thyroid dysfunction that is caused by pathology extrinsic to the thyroid gland. This is usually emanating from the central nervous system (CNS) as opposed to an ectopic location somewhere else in the body. The CNS pathology is most commonly a pituitary tumor and more rarely a tumor of the hypothalamus. In secondary hypothyroidism, the TSH and T4 are low, and in secondary hyperthyroidism the TSH and T4 are elevated. When monitoring therapies aimed at normalizing thyroid function, the overall goal is to normalize TSH or T4 levels in or near the reference range. ©2021 eviCore healthcare. All Rights Reserved. 4 of 23 400 Buckwalter Place Boulevard, Bluffton, SC 29910 (800) 918-8924 www.eviCore.com
Lab Management Guidelines V2.0.2021 In non-pregnant individuals, serum free thyroxine (free T4; CPT 84439) is the primary test used to confirm a suspected diagnosis of thyroid dysfunction and then monitor treatment.4,11-13 This test is done by automated immunoassay and there are many FDA- approved laboratory instruments. In practice, the automated immunoassay for free T4 has minimized the need for the T4 by elution test (CPT 84437), which is a complex method for producing a free T4 result based on high performance liquid chromatography (HPLC) with mass spectrometry. Thyroxine, CPT 84436, with Thyroid Hormone (T3 or T4) Resin Uptake or Thyroid Hormone Binding Ratio, CPT 84479 In pregnant individuals, total thyroxine (total T4) is generally more useful than free T4 unless trimester specific reference ranges for free T4 are available and the method of measurement remains constant throughout pregnancy. 14 In pregnant individuals, the total T4 is often used to calculate a free thyroxine index (FTI). It is a calculated quantity that estimates free T4 by multiplying the total T4 by the result of the T3 resin uptake assay. A version of T3 resin uptake (based on normalization), known as a thyroid binding hormone ratio (THBR) can replace the T3 resin uptake in the calculation. 8 The purpose of the T3 resin uptake or THBR test is to give an estimate of the number of binding sites available on thyroxine binding globulin, which is the main transport protein for T4. T3 resin uptake and THBR are measured by immunoassay. Triiodothyronine (T3), CPT 84480, 84481 T3 is produced from T4 in the liver and T3 is primarily what influences end organs and creates the clinical effects of hyperthyroidism and hypothyroidism. T3 is generally not used for screening for thyroid dysfunction.4,9-11,15 However, in some less common cases of hyperthyroidism a T3 within the reference range is also needed to rule out hyperthyroidism.11 In general, T3 is elevated in hyperthyroidism and decreased in hypothyroidism. The test comes in two forms. The first is a total T3, which is done by an automated immunoassay performed on a variety of FDA-approved instruments. The second test is a free T3 which measures the active unbound T3 and is done by a more cumbersome immunoassay. In practice, the tests can be used interchangeably in most, but not all, clinical situations and the total T3 is used preferentially for convenience. 9-11 TSH Receptor Antibodies (TRAb), CPT 83519, 83520 and Thyroid Stimulating Immunoglobulins (TSI), CPT 84445 Thyroid Testing The main purpose of TRAb testing is to confirm a diagnosis of Grave’s disease. TRAb can be measured by a number of laboratory techniques, some of which are coded as automated immunoassays, performed on a variety of FDA-approved platforms. 7 Alternatively, an older but very useful measurement of TRAbs is called thyroid stimulating immunoglobulins (TSI) which is performed by immunoassay. 11 ©2021 eviCore healthcare. All Rights Reserved. 5 of 23 400 Buckwalter Place Boulevard, Bluffton, SC 29910 (800) 918-8924 www.eviCore.com
Lab Management Guidelines V2.0.2021 Microsomal Antibodies (Also Known as anti-Tissue Peroxidase Antibodies (TPOAb)), CPT 86376 TPOAb (microsomal antibodies) testing is not a recommended screening test for either hypothyroidism or hyperthyroidism.4,11 A positive TPOAb test is used commonly to confirm a diagnosis of Hashimoto’s thyroiditis in individuals who have screened positive for hypothyroidism by virtue of an elevated TSH and depressed T4. 4,9 Another common use of TPOAb is to identify individuals at risk for progression to overt hypothyroidism caused by Hashimoto’s thyroiditis in those with subclinical hypothyroidism based on the initial screening evaluation of an elevated TSH and T4 within the reference range.4 Other uses concern determining if thyroid nodules are due to an autoimmune process or if recurrent miscarriage is related to autoimmune hypothyroidism.4,14 A rare use is as a secondary marker in Grave’s disease if the clinical index of suspicion is high and the TRAb and TSI testing is indeterminate. 10,11 The test is performed by immunoassay. Thyroxine Binding Globulin, CPT 84442 Thyroxine binding globulin (TBG) is the main transport protein for the thyroid hormones, T3 and T4. It is not used for screening for thyroid disease. 4,9-11 It is a rarely used test that can occasionally be useful in interpreting T3 or T4 values that do not match the clinical presentation and are therefore diagnostic conundrums. 9,10 Such situations can arise in inherited and other diseases that affect the level of thyroxine binding globulin. The test is performed by immunoassay. Thyroglobulin (Tg), CPT 84432 and Thyroglobulin Antibody (anti-Tg Ab), CPT 86800 The main use of Tg and anti-Tg Ab testing is in the staging and monitoring of differentiated thyroid cancers (DTC), over 97% of which are classified as papillary carcinoma (85%) or follicular thyroid carcinomas (12%). 12,13 Tg is a useful tumor marker for staging the cancer and monitoring treatment. Anti-Tg Ab must be measured prior to measuring Tg as Anti-Tg Ab occurs in up to 25% of individuals, and in their presence can interfere with the Tg assay. Individuals who have Anti-Tg Abs detected then are directed to use a more complex measurement of thyroglobulin based on mass spectrometry or radioimmunoassay (RIA) rather than usual first-line thyroglobulin measurement, which is by immunoassay when no Anti-Tg Abs are detected. 9,10,12,16 Tg Thyroid Testing or anti-Tg Ab testing has no role in screening for hypothyroidism or hyperthyroidism. 4,9- 11 Reverse T3, CPT 84482 The utility of reverse T3 remains controversial.17 Reverse T3 is not a recommended screening test for either hypothyroidism or hyperthyroidism. 4,11 In addition, reverse T3 does not appear as either a screening or confirmatory test in standard algorithms for evaluating thyroid dysfunction, nor does it appear in academic reviews of useful thyroid testing.7-10 The test is performed by tandem mass spectrometry. ©2021 eviCore healthcare. All Rights Reserved. 6 of 23 400 Buckwalter Place Boulevard, Bluffton, SC 29910 (800) 918-8924 www.eviCore.com
Lab Management Guidelines V2.0.2021
“Reverse T3 (rT3) is an inactive metabolite of thyroxine. It is widely measured by
alternative health practitioners to justify the use of T3 therapy and supplements thought
to enhance the conversion of T4 to T3. It has extremely limited utility for conventional
medical practitioners for assessing rare conditions such as consumptive
hypothyroidism, MCT8 or SBP2 mutations, or possibly distinguishing central
hypothyroidism from nonthyroidal illness in critically ill hospitalized patients.” 8
Guidelines and Evidence
Introduction
There are a number of guidelines, expert reviews, and algorithms from academic
practices and professional societies related to the function, diagnosis and screening of
thyroid disorders.1,4,5,7-15,18 These also discuss the evaluation and management of
thyroid nodules and associated malignancies and the further evaluation and monitoring
of individuals who are confirmed to have overt or subclinical thyroid disease after
screening.
Screening for Thyroid Disease
There is a continuum of screening between population screening for thyroid disease
and “aggressive case finding.”18,19 In population screening, all of the population, or a
large part of it, are screened by laboratory testing. In aggressive case finding, people
are screened based on criteria indicating they are at risk for a disease. 19
Garber and colleagues (2012) published guidelines for the American Association of
Clinical Endocrinologists (AACE) and the American Thyroid Association (ATA), which
were endorsed by the American Association of Diabetes Educators, the American
Academy of Otolaryngology-Head and Neck Surgery, and the American College of
Endocrinology (ACE).4 According to these guidelines there is no consensus among
panels of experts regarding population screening for thyroid dysfunction. 4
“expert panels have disagreed about TSH screening of the general population.”
The United States Preventive Services Task Force (USPSTF) concluded: 18
“that the current evidence is insufficient to assess the balance of benefits and
harms of screening for thyroid dysfunction in nonpregnant, asymptomatic adults.”
Thyroid Testing
In contrast, the joint AACE/ATA guidelines recommend screening: 4
“Screening for hypothyroidism should be considered in patients over the age of 60.”
There is widespread agreement that “aggressive case finding” is useful to detect
thyroid dysfunction. This means that screening is considered useful in a large variety
and number of individuals with enhanced risk for either hyperthyroidism or
hypothyroidism based on their history and physical. 4,19
Hennessey and colleagues wrote the official position of the AACE and ACE regarding
the importance of aggressive case finding for both hypothyroidism and
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hyperthyroidism.19 This was in response to the USPSTF conclusion regarding
insufficient evidence to support population screening. 18 They emphasized the
importance of laboratory testing for aggressive case finding in thyroid dysfunction since
the testing is effective and inexpensive treatments are often available.
“Given the lack of specificity of thyroid-associated symptoms, the appropriate
diagnosis of thyroid disease requires biochemical confirmation. The Thyroid
Scientific Committee of the AACE has produced this White Paper to highlight the
important difference between screening and case-based testing in the practice of
clinical medicine. We recommend that thyroid dysfunction should be frequently
considered as a potential etiology for many of the nonspecific complaints that
physicians face daily. The application and success of safe and effective
interventions are dependent on an accurate diagnosis. We, therefore, advocate for
an aggressive case-finding approach, based on identifying those persons most
likely to have thyroid disease that will benefit from its treatment.”
The ATA guideline on thyroid nodules in adults and children strongly supports
laboratory testing with TSH in individuals with a thyroid nodule >1cm in diameter. 12,13
“Serum thyrotropin (TSH) should be measured during the initial evaluation of a
patient with a thyroid nodule.”12
The joint AACE/ATA task force completed an exhaustive literature review and provided
a list of findings that support aggressive case finding with laboratory testing for
hypothyroidism. These findings include, but are not limited to: 4
A history of coexisting autoimmune disorders such as Type 1 Diabetes or pernicious
anemia
A family history of autoimmune thyroid disease in a first-degree relative
Abnormal thyroid exams
Previous thyroid surgery or thyroid disease
History of radiation treatment to the thyroid (beam radiotherapy and/or radioactive
iodine)
Current treatment with lithium or amiodarone
Presence of a psychiatric disorder
Infertility
Thyroid Testing
A large and varied list of ICD codes describing alopecia, fatigue and malaise,
weight gain, skin texture changes, vitiligo, disorders of menstruation, and a number
of cardiac findings including rhythm abnormalities, EKG changes such as a
prolonged QT interval, or the presence of congestive heart failure.
The joint AACE/ATA guideline goes on to state: 4
“Aggressive case finding” should be considered in those at increased risk for
hypothyroidism.”
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The recommendations for aggressive case finding in pregnant individuals or individuals
seeking to become pregnant are quite similar in the joint AACE/ATA guideline, as well
as in a separate guideline from the ATA that is specific to thyroid disease in pregnancy
and the postpartum period.4,14 These guidelines recommend against universal
screening of pregnant individuals or those planning pregnancy, but recommend
aggressive case finding in pregnant individuals with any of the many signs, symptoms,
and comorbid conditions associated with hypothyroidism. This recommendation also
includes any individuals seeking care for infertility. 4,14
Guidelines from the American College of Obstetricians and Gynecologists (ACOG)
have similar guidance recommending against universal screening of thyroid disease in
pregnant individuals:20
“Universal screening for thyroid disease in pregnancy is not recommended because
identification and treatment of maternal subclinical hypothyroidism has not been
shown to result in improved pregnancy outcomes and neurocognitive function in
offspring.”
In addition, the ATA guideline regarding thyroid disease in pregnancy and the
postpartum period recommends universal newborn screening: 14
“All newborns should be screened for hypothyroidism by blood spot analysis
typically 2-5 days after birth.”
Thus, across a broad variety of individuals, there is a reasonable expectation, based
on the guidance of expert panels, that testing for an initial diagnosis of a thyroid
disease--whether it be hypothyroidism, hyperthyroidism, or the evaluation of thyroid
nodules---will be fairly common given the high prevalence of treatable disease in the
population and the wide variety of signs, symptoms, and comorbid conditions
associated with thyroid diseases.
Specific Thyroid Tests for Screening for and Monitoring Thyroid Disease
Thyroid Stimulating Hormone (TSH, Thyrotropin), CPT 84443
Thyroxine (T4)
Thyroxine T4, Total, CPT 84436
Thyroid Testing
Thyroxine T4 requiring elution, CPT 84437
Free Thyroxine (free T4), CPT 84439
Thyroid Hormone (T3 or T4) Uptake or Thyroid Hormone Binding Ratio (THBR), CPT
84479
Triiodothyronine (T3)
Triiodothyronine (T3), CPT 84480
Free Triiodothyronine (T3), CPT 84481
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Judicious Test Use in the Screening for Thyroid Disease
The joint ASCP-Choosing Wisely guidance regarding screening for thyroid dysfunction
states:15
"Don't order multiple tests in the initial evaluation of a patient with suspected non-
neoplastic thyroid disease. Order thyroid-stimulating hormone (TSH), and if
abnormal, follow up with additional evaluation or treatment depending on the
findings. The TSH test can detect subclinical thyroid disease in patients without
symptoms of thyroid dysfunction. A TSH value within the reference interval excludes
the majority of cases of primary overt thyroid disease. If the TSH is abnormal,
confirm the diagnosis with free thyroxine (T4)."
According to the current ATA guideline for hyperthyroidism screening, TSH is the best
single test to diagnose hyperthyroidism, and in some cases with higher pretest
probability of disease, the diagnosis is aided by adding measurement of free T4 and
T3.11 The guideline makes the following statements regarding initial biochemical
evaluation by laboratory testing:11
“Serum TSH measurement has the highest sensitivity and specificity of any single
blood test used in the evaluation of suspected thyrotoxicosis and should be used as
an initial screening test. However, when thyrotoxicosis is strongly suspected,
diagnostic accuracy improves when a serum TSH, free T4, and total T3 are
assessed at the initial evaluation.”
Regarding testing in addition to TSH that that can be useful for screening individuals at
risk for hypothyroidism, the joint recommendation of AACE/ATA concluded--for
individuals who are not pregnant:4
“Apart from pregnancy, assessment of serum free T4 should be done instead of
total T4 in the evaluation of hypothyroidism. An assessment of serum free T4
includes a free T4 index or free T4 estimate and direct immunoassay of free T4
without physical separation using anti-T4 antibody”
The AACE/ATA task force goes on to declare that T3 measurements are not normally
indicated in screening for hypothyroidism:4
Thyroid Testing
“Serum total T3 or assessment of serum free T3 should not be done to diagnose
hypothyroidism.”
In addition, for pregnant individuals, the AACE/ATA guidelines make the following
modifications for screening for hypothyroidism because of the difficulty of accurately
measuring free T4 during some pregnancies: 4
“In pregnancy, the measurement of total T4 or a free T4 index, in addition to TSH,
should be done to assess thyroid status. Because of the wide variation in the
results of different free T4 assays, direct immunoassay measurement of free T4
should only be employed when method-specific and trimester-specific reference
ranges for serum free T4 are available.”
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Monitoring Thyroid Function and Disease
TSH is the most commonly used test for monitoring therapy for thyroid diseases. T4
and T3 play a less frequent but important role. A variety of guidelines explain the
plethora of uses of these tests for monitoring the thyroid in the context of treatments for
thyroid diseases.
For example, in non-pregnant individuals who have hypothyroidism: 4
“Patients being treated for established hypothyroidism should have serum TSH
measurements done at 4-8 weeks after initiating treatment or after a change in
dose. Once an adequate replacement dose has been determined, periodic TSH
measurements should be done after 6 months and then at 12-month intervals, or
more frequently if the clinical situation dictates otherwise.”
“Assessment of serum free T4, in addition to TSH, should be considered when
monitoring L-thyroxine therapy.”
In non-pregnant individuals with hyperthyroidism caused by Grave’s disease (GD) and
being treated with radioactive iodine (RAI): 11
“Follow-up within the first 1-2 months after RAI therapy for GD should include an
assessment of free T4 and total T3 and TSH. Biochemical monitoring should be
continued at 4-to-6 week intervals for 6 months, or until the patient becomes
hypothyroid and is stable on thyroid replacement”
In hypothyroidism of pregnancy being treated by L-thyroxine:
“Maternal serum TSH (and total T4) should be monitored every 4 weeks during the
first half of pregnancy and at least once between 26 and 32 weeks gestation and L-
thyroxine dosages adjusted as indicated.” 4
“In parallel to the treatment of hypothyroidism in the general population, it is
reasonable to target a TSH in the lower half of the trimester specific range. When
this is not available, it is reasonable to target maternal TSH concentrations below
2.5 mU/L.”14
In Grave’s Disease (GD) related hyperthyroidism of pregnancy being treated by anti-
Thyroid Testing
thyroid drugs (ATD):11
“GD during pregnancy should be treated with the lowest possible dose of ATD
needed to keep the mother’s thyroid hormone levels at or slightly above the
reference range for total T4 and T3 values in pregnancy (1.5 times above
nonpregnant reference ranges in the second and third trimesters), and the TSH
below the reference range for pregnancy. Similarly, free T4 levels should be kept at
or slightly above the upper limit of the pregnancy trimester reference range for the
assay. Thyroid function should be assessed at least monthly, and the ATD dose
adjusted, as required.”
Lastly, in thyroid cancer, the most common therapy for differentiated thyroid cancers is
full or partial thyroidectomy. The standard of care, as expressed in the ATA guideline,
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is chronic monitoring of TSH and, to a lesser extent, T4 with the goal of establishing
and maintaining adequate thyroid function with levothyroxine therapy after surgical
treatment.12 In addition, TSH measurement is part of the risk stratification strategy in
the guideline. The risk stratification is carried out multiple times over the course of
cancer monitoring.
Antibody Tests
1. TSH receptor antibodies (TRAb), CPT 83519, 83520
2. Thyroxine Stimulating Immunoglobulins (TSI), CPT 84445
3. Microsomal Antibodies (also known as anti-Tissue Peroxidase antibodies
(TPOAbs)), CPT 86376
TRAb/TSI
As described above, the current ATA guideline for hyperthyroidism screening states
TSH is the best single test to diagnose hyperthyroidism. 11 In some cases with
higher pretest probability of disease, the diagnosis is aided by adding
measurements of free T4 and T3. The guideline goes on to recommend
confirmatory laboratory testing for Grave’s Disease using TRAb and other
confirmatory diagnostics if:
o “the diagnosis is not apparent based on the clinical presentation and initial
biochemical evaluation”
Besides its use in confirmatory testing, TRAb is also used to monitor Grave’s
disease. For example, in individuals with Grave’s disease being treated with anti-
thyroid drugs (ATD), the ATA guideline states:11
o “Measurement of TRAb levels prior to stopping ATD therapy is suggested
because it aids in predicting which patients can be weaned from the medication,
with normal levels indicating greater chance for remission.”
And for pregnant women, the ATA guideline states: 14
o “If a patient is taking ATDs for treatment of Grave’s hyperthyroidism when
pregnancy is confirmed, a maternal serum determination of TRAb is
recommended” Thyroid Testing
o “If the patient requires treatment with ATDs for GD through midpregnancy, a
repeat determination of TRAb is again recommended at weeks 18-22." This
aforementioned guidance is also supported by the European Thyroid
Association.21
TPOAb
The AACE/ATA guideline for hypothyroidism states the main use of TPOAb, which
is now incorporated in published algorithms is to identify the inciting event. 4,9,10
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o “in patients with documented hypothyroidism, TPOAb identifies the cause” 4
In addition, the guideline recommends using TPOAb as a confirmatory diagnostic
test in individuals who have subclinical hypothyroidism, based on the initial
screening evaluation with TSH and free T4, since TPOAb identifies individuals at
risk for progression to overt hypothyroidism caused by Hashimoto’s thyroiditis. The
recommendation states:4
o “Anti-thyroid peroxidase antibody (TPOAb) measurements should be considered
when evaluating patients with subclinical hypothyroidism”
Other recommendations from the guideline regard using TPOAb to help determine
if an autoimmune hypothyroidism, either subclinical or overt, is causing thyroid
nodules or recurrent miscarriage.4
o “TPOAb measurement should be considered in order to identify autoimmune
thyroiditis when nodular thyroid disease is suspected to be due to autoimmune
thyroid disease.”
o “TPOAb measurements should be considered when evaluating patients with
recurrent miscarriage.”
In the treatment of primary hypothyroidism, the ATA guideline focuses on TSH
levels as a therapeutic endpoint with selected use of T4. TPOAb are not mentioned
regarding monitoring autoimmune hypothyroidism because once a person has
TPOAb, they persist throughout life despite successful treatment. 4
o “Once present, these antibodies generally persist, with spontaneous
disappearance occurring infrequently.”
Thyroglobulin and Thyroglobulin Antibody
1. Thyroglobulin, CPT 84432
2. Thyroglobulin Antibody, CPT 86800
Thyroglobulin is not a recommended screening test for either hypothyroidism or
hyperthyroidism.4,11 In addition, thyroglobulin is not recommended in the initial
Thyroid Testing
evaluation of a thyroid nodule by the ATA guidelines regarding thyroid nodules in adults
or children.12,13
“Routine measurement of serum thyroglobulin (Tg) for initial evaluation of thyroid
nodules is not recommended.”
“Serum Tg levels can be elevated in most thyroid diseases and are an insensitive
and nonspecific test for thyroid cancer.”
The ATA guidelines regarding thyroid nodules for adults and children summarize the
characteristics and uses of thyroglobulin (Tg) and thyroglobulin antibody (TgAb)
testing.12,13 The main use of thyroglobulin is in the postoperative staging and risk
stratification of thyroid malignancies, which can guide future disease monitoring and
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treatment. The guideline in children regarding differentiated thyroid cancer (DTC)
states:13
“..the measurement of serum Tg is a critical component in the management of the
pediatric DTC patient, both at the time of the initial postoperative staging…as well
as during long term surveillance and subsequent restaging…”
Similarly, the adult guideline for DTC also addresses using Tg for surveillance: 12
“Postoperative serum Tg (on thyroid hormone therapy or after TSH stimulation) can
help in assessing the persistence of disease or thyroid remnant and predicting
potential future disease recurrence. The Tg should reach its nadir by 3–4 weeks
postoperatively in most patients.”
The adult guideline states that measurement of Tg and TgAb (anti-Tg) should be
paired with TgAb analyzed first to determine Tg methodology : 12
“Serum Tg should be measured by an assay that is calibrated against the CRM457
standard. Thyroglobulin antibodies should be quantitatively assessed with every
measurement of serum Tg. Ideally, serum Tg and anti-Tg antibodies should be
assessed longitudinally in the same laboratory and using the same assay for a
given patient.”
The guideline in children emphasizes a similar point: 13
“TgAb are detected in up to 20%-25% of patients with DTC….and they interfere
with Tg measurements in a qualitative, quantitative, and method-dependent
manner, rendering the Tg level uninterpretable…All specimens sent for Tg
measurement require concomitant TgAb testing…”
Reverse T3, CPT 84482, and Thyroxine Binding Globulin, CPT 84442
Reverse T3 is not a recommended screening test for either hypothyroidism or
hyperthyroidism.4,11 The use of the test is controversial and the majority of the test
orders in the United States come from the workup of thyroid disease by alternative
practitioners.17
Thyroxine Binding Globulin (TBG) is not used for screening for thyroid disease or in the
Thyroid Testing
workup of thyroid nodules or cancer.4,11-13 It is a rarely used test that can occasionally
be useful in interpreting T3 or T4 values that do not match the clinical presentation and
are therefore diagnostic conundrums.9,10 Such situations can arise in inherited and
other diseases that affect the level of thyroxine binding globulin.
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Criteria
Introduction
This guideline outlines coverage criteria for in-vitro testing of blood or other body fluids
in the evaluation and management of thyroid disease. It does not address molecular
(i.e. nucleic acid) testing such as BRAF, and TERT mutations; anatomic pathology
examinations of fine needle aspirates or biopsies; imaging by any modality; or other
assessments of the thyroid besides in-vitro chemistry and antibody testing.
Thyroid Stimulating Hormone (TSH; Thyrotropin)
Test name and procedure code(s)
Test Name Procedure Code
Thyroid Stimulating Hormone (TSH; 84443
Thyrotropin)
Medical necessity requirements
TSH testing is indicated in the following circumstances:
o Signs and symptoms of hyperthyroidism or hypothyroidism
o Abnormal thyroid exam (e.g., enlarged thyroid) or thyroid imaging study
o Suspected iodine deficiency
o History of thyroid surgery, radiation treatment to thyroid, or treatment with anti-
thyroid drugs
o Monitoring thyroid treatment of overt or subclinical hypothyroidism, including but
not limited to levothyroxine therapy, watchful waiting, or immune modulating
therapies
o Monitoring treatment of overt or subclinical hyperthyroidism, including but not
limited to surgery, radioactive iodine, thyroid modifying drugs, or watchful waiting
o Monitoring and risk-stratifying treatment of thyroid cancers, including but not
limited to watchful waiting, surgery, radioactive active iodine, and anti-thyroid
Thyroid Testing
drugs
o History of a disorder that may be associated with thyroid disease (e.g., other
autoimmune conditions besides Grave’s disease or Hashimoto’s thyroiditis)
o Use of medications that may compromise thyroid function, such as lithium or
amiodarone
o Family history of thyroid disease in a first-degree relative
o Infertility
o Psychiatric disorder(s)
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Population-based thyroid disease screening with TSH is indicated for newborns and
people over age 60. Outside of these populations, population screening is not
indicated in the absence of symptoms or increased risk.
Thyroxine (T4) Testing
Test name and procedure code(s)
Test Name Procedure Code
Thyroxine (T4), Total 84436
Thyroxine (T4) requiring elution (e.g. 84437
neonatal thyroxine)
Free Thyroxine (free T4) 84439
Thyroid hormone (T3 OR T4) uptake or 84479
thyroid hormone binding ratio (THBR)
Medical necessity requirements
Thyroxine (T4) testing is indicated in the following circumstances:
o Signs and symptoms of hyperthyroidism or hypothyroidism
o Abnormal thyroid exam (e.g., enlarged thyroid) or thyroid imaging study
o Suspected iodine deficiency
o History of thyroid surgery, radiation treatment to thyroid, or taking anti-thyroid
drugs
o Monitoring thyroid treatment of overt or subclinical hypothyroidism, including but
not limited to levothyroxine therapy, watchful waiting, or immune modulating
therapies
o Monitoring treatment of overt or subclinical hyperthyroidism, including but not
limited to surgery, radioactive iodine, thyroid modifying drugs, or watchful waiting
Thyroid Testing
o Monitoring treatment of thyroid cancers, including but not limited to watchful
waiting, surgery, radioactive active iodine, and anti-thyroid drugs
o History of a disorder that may be associated with thyroid disease (e.g., other
autoimmune condition besides Grave’s disease or Hashimoto’s thyroiditis)
o Use of medications that may compromise thyroid function, such as lithium or
amiodarone
o Family history of thyroid disease in a first-degree relative
o Infertility
o Psychiatric disorder(s)
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Population-based thyroid disease screening is indicated for people over age 60.
Outside of these populations, population screening is not indicated in the absence
of symptoms or increased risk.
Only one form of thyroxine (T4) testing should be necessary per date of service and
the treating provider should select the single most informative test for the
circumstances. The only exception is when thyroid hormone (T3 or T4) uptake
(CPT 84479) is performed with total thyroxine (CPT 84436) to generate a free T4
index in pregnant women.
Billing and reimbursement
When testing is medically necessary:
o Because only one form of thyroxine testing is necessary per date of service, the
following billing limitations apply:
When CPT 84439 is billed with 84436 or 84437 or 84479, only 84439 will be
payable.
When CPT 84437 is billed with 84436 or 84479, only 84437 will be payable.
CPT 84436 is payable with CPT 84479.
Triiodothyronine (T3)
Test name and procedure code(s)
Test Name Procedure Code(s)
Triiodothyronine (T3) 84480
Free Triiodothyronine (free T3) 84481
Medical necessity requirements
Triiodothyronine (T3) testing is indicated in the following circumstances:
o Signs or symptoms of hyperthyroidism when T4 measurements are normal
o Monitoring treatment of overt or subclinical hyperthyroidism from any cause Thyroid Testing
T3 testing is not indicated for hypothyroidism screening and monitoring, or for
population-based thyroid disease screening.
Only one form of triiodothyronine (T3) testing should be necessary per date of
service and the treating provider should select the single most informative test for
the circumstances.
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Billing and reimbursement
T3 testing will not be payable when billed with a diagnosis of hypothyroidism,
including ICD E02 (Subclinical iodine-deficiency hypothyroidism), E03.X (Other
hypothyroidism), E89.0 (Postprocedural hypothyroidism).
When testing is medically necessary:
o Because only one form of T3 testing is necessary per date of service, when CPT
84480 is billed with 84481, only 84481 will be payable.
TSH Receptor Antibodies (TRAb/TSI)
Test name and procedure code(s)
Test Name Procedure Code(s)
TSH receptor antibodies (TRAb) 83519
TSH receptor antibodies (TRAb) 83520
Thyroid Stimulating Immunoglobulins 84445
(TSI)
Medical necessity requirements
TRAb or TSI testing is indicated for:
o Testing for Grave’s disease when screening results suggest hyperthyroidism
o Monitoring treatment of Grave’s disease
TRAb or TSI testing has no role in screening for hypothyroidism or hyperthyroidism
and is therefore not coverable in the absence of a specific indication
Only one form of TRAb or TSI testing should be necessary per date of service and
the treating provider should select the single most informative test for the
circumstances
Thyroid Testing
Billing and reimbursement
TRAb or TSI testing will be payable when billed with a diagnosis code in the E05.X
range (Thyrotoxicosis [hyperthyroidism]).
When testing is medically necessary:
o TRAb or TSI is allowed once per year to confirm or rule out a diagnosis of
Grave’s disease in a patient with hyperthyroidism.
o TRAb or TSI is allowed up to 4 times per year for monitoring Grave’s disease.
o Because only one form of TRAb or TSI testing is necessary per date of service,
only one of the following codes is allowed for such testing per date of service:
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CPT 83519
CPT 83520
CPT 84445
Microsomal Antibodies (anti-Tissue Peroxidase Antibodies (TPOAb))
Test name and procedure code(s)
Test Name Procedure Code(s)
Microsomal (Thyroid peroxidase) 86376
antibodies
Medical necessity requirements
TPOAb is indicated to:
o Confirm Hashimoto’s thyroiditis when screening results suggest hypothyroidism
o As a secondary confirmatory test for Grave’s Disease if the primary confirmatory
test, TRAb/TSI, is equivocal and the index of suspicion for Grave’s Disease
remains high
TPOAb is not indicated for monitoring the treatment of either Hashimoto’s thyroiditis
or Grave’s Disease.
TPOAb has no role in screening for hypothyroidism or hyperthyroidism and is
therefore not coverable in the absence of a specific indication.
Billing and reimbursement
TPOAb is allowed once per year to confirm or rule out a diagnosis of Hashimoto’s
thyroiditis.
TPOAb is allowed once per year to confirm or rule out a diagnosis of Grave’s
disease.
Thyroglobulin (Tg) and Thyroglobulin Antibody (anti-Tg Ab)
Thyroid Testing
Test name and procedure code(s)
Test Name Procedure Code(s)
Thyroglobulin 84432
Thyroglobulin antibody 86800
Medical necessity requirements:
Tg is indicated to:
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o Monitor the treatment of invasive or metastatic thyroid cancer
o Help risk stratify thyroid cancers
Anti-Tg Ab is indicated as an aid for interpreting the Tg test.
Tg and anti-Tg Ab have no role in screening for hypothyroidism or hyperthyroidism
and are therefore not coverable in the absence of a specific indication.
Billing and reimbursement
Tg and/or anti-Tg Ab testing will be payable when billed with a diagnosis code in
Table: Thyroglobulin (CPT 84432) and Thyroglobulin Antibody (CPT 86800)
Indications.
When testing is medically necessary:
o Tg and anti-Tg Ab are allowed up to 6 times per year to monitor the treatment of
invasive or metastatic thyroid cancer and provide an aid to risk stratification of
the cancer.
o Anti-Tg Ab should be measured prior to Tg measurement to determine whether
typical immunoassay measurement of Tg is appropriate, or if the presence of
anti-Tg Ab necessitates measurement of Tg by an alternate method (e.g. mass
spectrometry, RIA).
Reverse T3
Test name and procedure code(s)
Test Name Procedure Code(s)
Reverse T3 84482
Medical necessity requirements
There are no indications for reverse T3 testing that are supported by current
guidelines or the medical literature. Therefore, reverse T3 testing is considered
Thyroid Testing
experimental/investigational/unproven.
Thyroxine Binding Globulin
Test name and procedure code(s)
Test Name Procedure Code(s)
Thyroxine Binding Globulin (TBG) 84442
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Medical necessity requirements
TBG is indicated as a secondary test for interpreting T4 results that are diagnostic
conundrums and where a binding globulin disorder is suspected as an explanation
for the unexpected T4 result.
TBG has no role in screening for hypothyroidism or hyperthyroidism and is
therefore not coverable in the absence of a specific indication.
Table: Thyroglobulin (CPT 84432) and Thyroglobulin Antibody (CPT 86800)
Indications
ICD10 Codes and Descriptions
ICD Code(s) ICD Description(s)
C73 Malignant neoplasm of thyroid gland
D49.7 Neoplasm of unspecified behavior of
endocrine glands and other parts of
nervous system
Z08 Encounter for follow-up examination after
completed treatment for malignant
neoplasm
Z51.0 Encounter for antineoplastic radiation
therapy
Z51.11 Encounter for antineoplastic
chemotherapy
Z51.12 Encounter for antineoplastic
immunotherapy
Z85.850 Personal history of malignant neoplasm of
thyroid
Z85.858 Personal history of malignant neoplasm of
endocrine glands
Thyroid Testing
References
Introduction
These references are cited in this guideline.
1. Thyroid Diseases (2020). Lab Tests Online. American Association for Clinical
Chemistry. https://labtestsonline.org/conditions/thyroid-diseases
2. Hollowell JG, Staehling NW, Flanders WD, et al. Serum TSH, T(4), and thyroid
antibodies in the United States population (1988 to 1994): National Health and
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Nutrition Examination Survey (NHANES III). J Clin Endocrinol Metab. 2002;87:489-
99.
3. Canaris GJ, Manowitz NR, Mayor G, Ridgway EC. The Colorado thyroid disease
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4. Garber JR, Cobin RH, Gharib H, et al. American Association of Clinical
Endocrinologists and American Thyroid Association Taskforce on Hypothyroidism
in Adults. Clinical practice guidelines for hypothyroidism in adults: cosponsored by
the American Association of Clinical Endocrinologists and the American Thyroid
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5. Helfand M. Screening for Thyroid Disease. Systematic Evidence Review No. 23.
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stimulating hormone testing-optimizing pre-conception health or generating toxic
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7. Ross DS (2017a). Diagnosis of and screening for hypothyroidism in nonpregnant
adults. In JE Mulder (Ed.), UpToDate. Retrieved August 31, 2018.
8. Ross DS (2017b). Laboratory assessment of thyroid function. In JE Mulder (Ed.),
UpToDate. Retrieved August 31, 2018.
9. Thyroid function ordering algorithm (2020). Mayo Foundation for Medical Education
and Research.
https://www.mayomedicallaboratories.com/it-mmfiles/Thyroid_Function_Ordering_
Algorithm.pdf
10. Thyroid disorders testing algorithm (2020). ARUP Consult, an ARUP test selection
tool for healthcare professionals. https://arupconsult.com/algorithm/thyroid-
disorders-testing-algorithm
11. Ross DS, Burch HB, Cooper DS, et al. 2016 American Thyroid Association
guidelines for diagnosis and management of hyperthyroidism and other causes of
thyrotoxicosis. Thyroid. 2016;26(10):1343-1421.
12. Haugen BR, Alexander EK, Bible KC, et al. 2015 American Thyroid Association
Thyroid Testing
management guidelines for adult patients with thyroid nodules and differentiated
thyroid cancer. Thyroid. 2016;6(1):1-133.
13. Francis GL, Waguespack SG, Bauer AJ, et al. Management guidelines for children
with thyroid nodules and differentiated thyroid cancer. Thyroid. 2015;25(7):716-59.
14. Alexander EK, Pearce EN, Brent GA, et al. 2017 guidelines of the American
Thyroid Association for the diagnosis and management of thyroid disease during
pregnancy and the postpartum. Thyroid. 2017;27(3):315-389.
15. Twenty things physicians and patients should question (2015). Choosing Wisely
and the American Society for Clinical Pathology. Available at:
http://www.choosingwisely.org/wp-content/uploads/2015/02/ASCP-Choosing-
Wisely-List.pdf
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16. Cooper DS, Doherty GM, Haugen BR, Kloos RT, Lee SL, Mandel SJ, Mazzaferri
EL, McIver B, Pacini F, Schlumberger M, Sherman SI. Revised American Thyroid
Association management guidelines for patients with thyroid nodules and
differentiated thyroid cancer: the American Thyroid Association (ATA) guidelines
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1;19(11):1167-214.
17. Schmidt RL, LoPresti JS, McDermott MT, et al. Does reverse triiodothyronine
testing have clinical utility? An analysis of practice variation based on order data
from a national reference laboratory. Thyroid. 2018;28(7):842-848.
18. LeFevre ML. Screening for thyroid dysfunction. U.S. Preventive Services Task
Force Recommendation Statement. Ann Int Med. 2015;162:641-652. Available at:
https://www.uspreventiveservicestaskforce.org/Page/Document/UpdateSummaryFi
nal/thyroid-dysfunction-screening?ds=1&s=thyroid
19. Hennessey JV, Garber JR, Woeber KA, et al. American Association of Clinical
Endocrinologists and American College of Endocrinology position statement on
thyroid dysfunction case finding. Endocr Pract. 2016;22(2):262-70.
20. American College of Obstetricians and Gynecologists. Thyroid Disease in
Pregnancy: ACOG Practice Bulletin, Number 223. Obstetrics and gynecology.
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Thyroid Testing
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