Understanding Flu Testing
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Tech_Bul_Flu.qxd 11/18/05 4:15 PM Page 1
TECHNICAL BULLETIN
Vol. 1 No. 2, August 2005
Understanding Flu Testing
Flu Facts
1
Choosing a Rapid Flu A+B Test
2
Improved Medical Outcomes
4
Enhanced Economic Value
5
BD Directigen™ EZ Flu A+B Technology:
8 Two-step lateral flow process enhanced
by proprietary reagents
BD Directigen™ EZ Flu A+B Technology:
9 Optimal readability
Tech_Bul_Flu.qxd 11/18/05 4:15 PM Page 3
Flu Facts 1
● The flu is a contagious respiratory illness caused by influenza
viruses. Influenza A and B are the two types of influenza
viruses that cause epidemic human disease. Influenza C
usually causes mild upper respiratory tract disease and, as
such, is not as important clinically.
● Influenza A viruses are further categorized into subtypes on
the basis of two surface antigens: hemagglutinin (H) and
neuraminidase (N). For example, H3N2 is the strain that has
caused flu infections in recent years.
● In the U.S., more than 200,000 people are hospitalized each
year from flu-related complications.1
● Approximately 36,000 people die from flu every year.2
● Flu-related costs are estimated to be anywhere from $12-20
billion annually.3
● High-risk populations for serious flu complications include:
■ older adults
■ young children
■ those with certain health conditions, including pregnancy
● Diagnosis is most often determined clinically, based on
symptoms during the appropriate time of year if disease is
occurring in the community. Diagnostic tests are performed
whenever diagnosis is uncertain and therapy is being
considered. The FDA has cautioned healthcare professionals
regarding the dangers of prescribing antiviral drugs for
influenza based simply on clinical interpretation without
a definitive flu diagnosis.4
1
As reported at the CDC website: http://www.cdc.gov/flu/about/qa/hospital.htm
2
The CDC MMWR report P1, May 28, 2004/Vol. 53/HR-6
3
Flu season could cost $20B. (2004, October 14). Retrieved from CNN website:
http://money.cnn.com/2004/10/18/news/economy/flu_costs/
4
As reported at the FDA website: http://www.fda.gov/bbs/topics/ANSWERS/ANS00995.html
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2 Choosing a Rapid Flu A+B Test
There are currently several rapid Flu A+B tests available utilizing
two major technologies, enzyme immunoassay (EIA) and
chromatographic immunoassay (lateral flow). Each test type
offers a wide range of performance and specimen choices. Key
factors that each laboratory should be aware of when choosing a
rapid Flu A+B test include:
● Test accuracy
● Ability to differentiate Flu A and Flu B
● Turnaround time
● Choices of specimen type
● Choices of transport medium
● Financial impact including reimbursement
● Reliable supply
BD Diagnostics provides two choices for rapid Flu A+B
testing: the BD Directigen™ Flu A+B test and the
BD Directigen EZ Flu A+B test.
BD Directigen™ Flu A+B Test
Built on enzyme
immunoassay technology.
BD Directigen™ EZ Flu A+B Test
Built on lateral flow technology.
TECHNICAL BULLETINTech_Bul_Flu.qxd 11/18/05 4:15 PM Page 5
Choosing a Rapid Flu A+B Test (continued) 3
VOL. 1 NO. 2, AUGUST 2005Tech_Bul_Flu.qxd 11/18/05 4:15 PM Page 6
4 Improved Medical Outcomes
The use of a rapid test kit with increased sensitivity can result in
more accurate patient diagnosis. Improper diagnosis of influenza
can lead to inappropriate use of antibiotics, lack of appropriate
antiviral therapy and increased spread of influenza to high-risk
patients and others in the community.
In addition to being the first differentiated flu kit on the market,
the high accuracy of the BD Directigen™ Flu A+B kit has made it
the #1 rapid Flu A+B test used by hospital labs.
As the innovator of lateral flow technology, BD is pleased to take
flu testing to a new level of performance with the lateral flow-
based BD Directigen EZ Flu A+B test.
The BD Directigen EZ Flu A+B test ensures accurate and rapid
results. As such, using this test benefits patients by enabling
physicians to prescribe the most effective treatment in the most
timely manner.
TECHNICAL BULLETINTech_Bul_Flu.qxd 11/18/05 4:15 PM Page 7
Enhanced Economic Value 5
There are several financial aspects that should be considered when
deciding on a Flu A+B kit:
● Financial impact related to reimbursement and
regulatory considerations
● Financial impact to your laboratory
● Financial impact to patient care
I. Financial Impact - Reimbursement
Correct coding and subsequent reimbursement for any laboratory
procedure, including influenza tests, can be a challenging process.
Factors to be aware of when choosing a platform for influenza
testing include:
1. CLIA Waived vs. Moderately Complex Tests
2. Non-differentiated vs. Differentiated Tests
● Tests that identify influenza, but cannot
differentiate flu A and flu B may be
reimbursed only once.
● Tests that differentiate flu A and flu B may be
billed twice, only if separate test procedures are
conducted with separate test results, and a physician
specifically orders both tests.
For differentiated tests:
3. Single Step vs. Multiple Step Tests
● For tests with a single step, an applicable single
step code or the general methodology code (e.g.,
87449, 87899) should be used. Reimbursement is
less for single step tests due to reduced resource
and time intensity.
● The multiple step CPT code 87400 applies to enzyme
immunoassay (EIA) tests requiring multiple steps.
Reflecting required resources, multiple step codes
generally have higher reimbursements than single
step codes.
continued on page 6
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6 Enhanced Economic Value (continued)
4. Single Test vs. Multiple Test Procedures
● If a single test procedure is used to differentiate
between flu A and flu B, then the appropriate
CPT code may be billed once.
● If separate tests are conducted to separately identify
both flu A and flu B, and a physician specifically
orders both tests, then the appropriate CPT code may
be billed twice.
II. Financial Impact - Your Laboratory
A lot of time and many resource hours can be spent on validating
specific transport media and specimen type requirements.
Choosing a differentiated Flu A+B test with maximum flexibility
in these areas can result in considerable savings in time and
money for your laboratory.
Transport Media
The following transport media have been tested and found to
be compatible with the BD Directigen™ EZ Flu A+B test*:
Bartel ViraTrans™ Medium PBS plus 0.5% BSA
Cellmatics™ PBS plus 0.5% gelatin
Earle’s Minimal Essential Medium (EMEM) Phosphate Buffered Saline (PBS)
EMEM plus 0.5% BSA Starplex Multitrans™
EMEM plus 1% BSA Sucrose Phosphate (2-SP)
Hank’s Basal Salt Solution Trypticase™ Soy Broth
M4 Medium Trypticase Soy Broth + 0.5% gelatin
M4 RT Medium Trypticase Soy Broth + 0.5% BSA
M5 Medium Veal Infusion Broth (VIB)
Normal Saline** VIB plus 0.5% BSA
BD™ Universal Viral Transport Medium
* Other transport media may be utilized if an appropriate qualification exercise is performed.
** Frozen storage of specimens collected in normal saline is not recommended for testing with the
BD Directigen EZ Flu A+B test.
TECHNICAL BULLETINTech_Bul_Flu.qxd 11/18/05 4:15 PM Page 9
Enhanced Economic Value (continued) 7
III. Financial Impact - Patient Care
Increasingly, more adults are being treated for the flu due to an
increased availability of antiviral drugs. Common antiviral drugs
for influenza fall into one of two categories: those that are
influenza A specific, and those that treat both influenza A and B.
The combined influenza A+B drugs (zanamivir and oseltamivir)
are significantly more expensive than those that are influenza A
specific (amantadine and rimantadine).
The use of a differentiated flu test, which provides separate
results for both flu A and flu B, enables the use of targeted
antiviral therapies that treat specifically for either flu A or flu B.
When using other flu tests that do not differentiate between flu A
and flu B, treatment must rely on the more expensive broad-
spectrum antiviral drugs.
Improper diagnosis of influenza can also result both in improper
therapy as well as continued spread of the disease to high-risk
patients and others in the community.
1
Costs are from http://www.walgreens.com/ on 08.16.05
2
Costs are from http://www.drugstore.com/ on 08.16.05
3
Cost is for a 30-tab packet
4
Cost is for a 60-tab packet
5
Cost is for 20 doses
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8 BD Directigen™ EZ Flu A+B Technology:
Two-step lateral flow process enhanced by proprietary reagents
The BD Directigen EZ Flu A+B test utilizes
a unique, patented form of lateral flow
technology invented by BD. This
technology enables a simpler workflow
while providing maximum performance
and easy readability.
In order to detect all subtypes of influenza
A strains and influenza B strains, rapid flu
tests are typically designed to detect the
influenza nucleoprotein. The nucleoprotein
resides within the virus and is well
conserved among subtypes. As a result,
viral extraction is necessary to release the
nucleoprotein and maximize detection.
The BD Directigen EZ Flu A+B test
utilizes a proprietary sample processing Illustration 1
reagent specially developed to break down Influenza antigen release
mucoid specimens for maximal antigen without sample processing.
release (compare illustrations 1 and 2).
Increased antigen release can allow for
improved sensitivity.
Other lateral flow Flu A+B tests may lack
the sample processing step or may require
that mucoid samples be sonicated prior
to testing.
Illustration 2
Influenza antigen release
after sample processing.
TECHNICAL BULLETINTech_Bul_Flu.qxd 11/18/05 4:16 PM Page 11
BD Directigen™ EZ Flu A+B Technology: 9
Optimal readability
The BD Directigen EZ Flu A+B test is designed for easy readability.
Variations in test line intensity are typically seen with
chromatographic (lateral flow) immunoassays. The sample
processing reagent in the BD Directigen EZ Flu A+B test helps
create a clear white to light pink background in the test result
window. This allows for easier-to-read test lines. Optimized
concentrations of antibodies and detector provide clearer test
lines that are easier to read even with weak-positive samples.
Some of the many benefits of the BD Directigen EZ Flu A+B
test include great performance, increased laboratory efficiency
and enhanced economic value.
Great Performance:
● Analytical testing demonstrates ability to detect H5N1
isolates and the A/California/07/2004 strain
● High accuracy to ensure proper diagnosis:
Flu A Flu B
Accuracy* 95.5% 96.8%
Increased Laboratory Efficiency:
● Single device for both flu A and flu B
● Proprietary reagent for making mucoid samples easy to test
● Easy-to-read test line for rapid result determination
● Results in only 15 minutes with simple-to-use workflow
● Convenient room temperature storage
Enhanced Economic Value:
● Separate test wells for flu A and flu B allows for separate
multi-step test reimbursement
● Compatible with a wide variety of transport media saving
time and resources required for validation
● Liquid positive and negative controls assists with
QC compliance
● Acceptable for use with multiple specimen types minimizing
specimen incompatibility and rejection:
● Nasopharyngeal washes
● Nasopharyngeal aspirates
● Throat swabs
* Accuracy based on nasopharyngeal wash and nasopharyngeal aspirate data.
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➤ Featured in this bulletin:
Cat. No. Quantity Description
256050 30 tests Directigen™ EZ Flu A+B Kit
256010 20 tests Directigen™ Flu A+B Kit
Other BD Directigen™
Respiratory Testing Products:
Cat. No. Quantity Description
256030 30 tests Directigen™ EZ RSV Kit
253020 20 tests Directigen™ RSV Kit
253040 40 tests Directigen™ RSV Kit
256017 30 tests Directigen™ EZ Group A Strep Kit
BD Diagnostics
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