Many countries including Germany are recommending to use the rapid tests for Influenza A and B to test for Swine flu. These tests detect an infection with several Influenza strains including H1N1 within 15 minutes and the sensitivity and specificity levels are sufficiently high to give doctors important extra information for clinical decision making. In connection with the clinical symptoms  and ideally some other simple rapid tests (to differentiate between bacterial and viral infections such as neopterin and ESR), the outcome of the test will help to avoid treatment with antivirals with potential side effects or will support the decision to use antiviral treatment with tamiflu or relenza (oseltamivir and zanamivir) . At the same time other infections such as tonsillitis will not be misdiagnosed as a possible swine flu and not treated appropriately. Without testing patients and doctors are completely blind what they treat.   

The test can be performed in our practice or can be ordered from here for home testing through the patient him/herself. It is easy to perform from the back of the throat (no blood required just a swab with cotton wool) and simple to interpret. The result can be reported to the doctor by the patient and necessary steps can be taken.

Order here: info(at)Internationale-praxis.de

The price for one test is: 45 Euros plus mail

Information for Health Care Professionals
May 2, 2009 10:00 PM ET

Background
Rapid influenza diagnostic tests can help in the diagnosis and management of patients who present with signs and symptoms compatible with influenza. Such tests detect seasonal influenza A and B viral nucleoprotein antigens in respiratory specimens. The currently circulating novel H1N1 influenza virus (also referred to as swine flu) is an influenza A virus. Data are not yet available to inform recommendations on the use of rapid influenza diagnostic tests in patients with novel H1N1 virus infection. It is reasonable to assume that rapid diagnostic tests that detect influenza A viral nucleoprotein antigen can detect novel H1N1 flu infection in respiratory specimens as these nucleoprotein antigens are highly conserved across influenza A viruses. However, the sensitivity and specificity of the different rapid tests is not yet known for this novel virus. CDC has received anecdotal reports of false positive and false negative results. Clinicians may consider using rapid diagnostic tests as part of their evaluation of patients with signs and symptoms compatible with influenza, but results should be interpreted with caution. Confirmation of novel H1N1 flu infection can only be made by reverse-transcription polymerase chain reaction (RT-PCR) or viral culture.

Reliability and Interpretation of Rapid Influenza Test Results
The reliability of rapid influenza diagnostic tests depends largely on the conditions under which they are used, and are entirely based on the experience with seasonal influenza

• For detection of seasonal influenza virus infection, sensitivities of rapid diagnostic tests are approximately 50-70% when compared with viral culture or RT-PCR, and specificities of rapid diagnostic tests for influenza are approximately 90-95%. Sensitivity and specificity of these tests for detection of the novel H1N1 flu virus are unknown.
• False-positive (and true-negative) results are more likely to occur when influenza is uncommon in the community, which is generally at the beginning and end of an outbreak.
• False-negative (and true-positive) results are more likely to occur when influenza is common in the community, which is typically at the height of an outbreak.
• Test sensitivity may vary depending on when in the course of illness the specimen is collected. Respiratory specimens for testing should be collected in the first 4-5 days of illness when viral shedding is greatest.

Given these limitations, the decision of whether or not to test patients with rapid influenza diagnostic tests should be based upon the patient’s presenting symptoms, whether or not cases of novel H1N1 have been confirmed in the area, and/or the patient’s risk for severe disease or other complications.

How to interpret a positive test result
A patient testing positive for influenza B by rapid diagnostic test likely has been infected with seasonal influenza B virus that is continuing to circulate or is a false-positive result. Such a patient is unlikely to have novel H1N1 virus infection.

There are several possibilities when a patient tests positive for influenza A by rapid antigen test:

• The patient might have novel H1N1 virus infection
• The patient might have seasonal influenza A virus infection or
• The patient might have a false positive test result.

Information provided by states and local health authorities should be consulted to determine whether public health authorities are advising that patients who test positive on a rapid influenza antigen test need additional testing. In areas with many new confirmed cases of novel H1N1 flu infection and where community spread of H1N1 is occurring, patients who test positive on a rapid influenza diagnostic test can be treated empirically with antiviral medications if clinically indicated (see Interim Guidance on Antiviral Recommendations for Patients with Novel Influenza A (H1N1) Virus Infection and Their Close Contacts) without further testing. In areas with no or few confirmed cases of novel H1N1 flu, a nasopharyngeal swab/aspirate or nasal aspirate should be collected and sent to the state public health laboratory for RT-PCR to determine if the patient has H1N1 infection, seasonal influenza A virus infection, or a false-positive test result. See Interim guidelines for specimen collection and Interim biosafety guidelines for laboratory workers.

How to interpret a negative result
Novel H1N1 flu virus infection cannot be excluded when a patient tests negative for influenza A by rapid antigen test. If the patient has an epidemiologic link to a confirmed case (i.e. had close contact with a confirmed case), or has either traveled to or resides in a community where there are one or more confirmed novel H1N1 cases, further testing and treatment should be based upon clinical suspicion, severity of illness, and risk for complications. If there is no epidemiologic link and the patient has mild illness, further testing and treatment are not recommended.

What is swine influenza?
Swine influenza (swine flu) is a respiratory disease of pigs caused by type A influenza viruses. This type of flu is normally restricted to pigs, but human infections can and do happen as evidenced by the current outbreak.

What is the influenza strain that is causing the current outbreak of swine flu in humans?
The swine flu virus involved in the current outbreak is a type A, H1N1 subtype, influenza virus.

How widespread is this strain?
The World Health Organization (WHO) is reporting confirmed cases of humans with swine influenza A/H1N1 in North America, South America, Europe and Asia. An updated case count of confirmed swine flu infections worldwide is available at www.who.int/csr/don/en.

How does the current swine A/H1N1 flu differ from A/H1N1 influenza previously known to infect humans?
According to CDC, H1N1 swine flu viruses are antigenically very different from human H1N1 viruses and, therefore, vaccines for human seasonal flu would not provide protection from H1N1 swine flu viruses. On the other hand, regions of the nucleoprotein antigen, targeted by most rapid diagnostic tests including the BinaxNOW test, are highly conserved between strains. This means that newly emergent strains often contain the same nucleoprotein sequences as previous strains in these conserved regions. Sequencing data submitted to GenBank reveals that this is also true for the new swine flu isolates. www.ncbi.nlm.nih.gov/genomes/FLU/SwineFlu.html

Does the BinaxNOW Influenza test detect this swine flu virus?
The BinaxNOW Influenza A & B Test detects the nucleoprotein antigen which is conserved and present in all influenza A strains and has been demonstrated to detect influenza A/H1N1 as reported in the product labeling. Human specimens from infected individuals are not yet accessible.  Therefore, the performance of current rapid point of care tests, including BinaxNOW, has not yet been established.

What is Inverness doing to validate the BinaxNOW test for detection of swine flu?
Inverness is working closely with CDC to identify options for accessing confirmed human specimens needed for this testing. We have offered the agency our full support and will collaborate in any way requested. Any updates will be posted to the Inverness website as they become available. www.invernessmedicalpd.com

Is this swine flu virus contagious?
CDC has determined that this swine influenza A (H1N1) virus is contagious and is spreading from human to human. However, at this time, it is not known how easily the virus spreads between people. www.who.int/csr/disease/swineflu/en/index.html

What are the signs and symptoms of swine flu in people?
The WHO states that the clinical symptoms are similar to seasonal influenza but reported clinical presentation ranges broadly from asymptomatic infection to severe pneumonia resulting in death.
www.who.int/csr/disease/swineflu/en/index.html

If I suspect that my patient is infected with swine flu, what should I do?
If you suspect a patient may be infected with influenza, it is recommended that you follow the government guidelines published by your country for the collection, storage and testing of samples.
For US customers, CDC recommends that you collect a nasopharyngeal swab or nasal wash/aspirate as soon as possible after illness onset. Specimens should be placed into 1-3 ml of sterile viral transport media (VTM) and immediately placed on ice or cold packs or at 4°C (refrigerator) for transport to the laboratory. Contact your public health laboratory immediately.

Because many state public health departments have established specimen collection and transport requirements based on their respective interpretations of CDC guidelines, check with your state public health laboratory for specific instructions. Additionally, consult CDC's website for the most recent information on preferred specimens and appropriate specimen storage. www.cdc.gov/swineflu/specimencollection.htm

For UK customers, consult the Health Protection Agency’s (HPA) website.
www.hpa.org.uk/web/HPAwebFile/HPAweb_C/1241048770758

How can I confirm that my patient has influenza caused by swine flu?
It is not possible for individual laboratories to perform confirmatory testing. In all suspected cases of influenza, it is recommended that you follow the government guidelines published by your country.
In the US, CDC is recommending that in all suspected cases of influenza, whether the rapid test is positive or negative, samples must be sent to state public health laboratories for confirmatory testing.

Can swab samples eluted in the Elution Solution provided in CLIA waived kits be sent in for confirmation testing?
Follow the government guidelines published by your country for the collection, storage and testing of suspected influenza samples.

In the US, CDC recommends that swab samples be collected in 1-3 ml of viral transport medium, such as M4RT or the BD Universal Viral Transport System. If you have already collected the swab in elution solution and the patient is not available for a second swab collection, send the residual elution solution sample for confirmatory RT-PCR testing, with a notation that the sample is in BinaxNOW elution solution. If your public health laboratory requires that the collected swab remain in the solution for transport, we recommend snipping the swab so that just the swab head remains in the solution and capping the vial for transport. Swab samples in elution solution are NOT appropriate for culture.