Detection of Influenza A virus subtype H1N1 using polymerase chain reaction technique
What is this test?
This test detects swine-origin influenza virus in secretions (fluid samples) from the nose, mouth, and throat. Swine-origin influenza is also called swine flu or H1N1 virus. This test is used to diagnose swine flu.
What are other names for this test?
- PCR test for H1N1 influenza A
- PCR test for swine influenza A
Why do I need this test?
Laboratory tests may be done for many reasons. Tests are performed for routine health screenings or if a disease or toxicity is suspected. Lab tests may be used to determine if a medical condition is improving or worsening. Lab tests may also be used to measure the success or failure of a medication or treatment plan. Lab tests may be ordered for professional or legal reasons. You may need this test if you have:
- H1N1 Flu
When and how often should I have this test?
When and how often laboratory tests are done may depend on many factors. The timing of laboratory tests may rely on the results or completion of other tests, procedures, or treatments. Lab tests may be performed immediately in an emergency, or tests may be delayed as a condition is treated or monitored. A test may be suggested or become necessary when certain signs or symptoms appear.
Due to changes in the way your body naturally functions through the course of a day, lab tests may need to be performed at a certain time of day. If you have prepared for a test by changing your food or fluid intake, lab tests may be timed in accordance with those changes. Timing of tests may be based on increased and decreased levels of medications, drugs or other substances in the body.
The age or gender of the person being tested may affect when and how often a lab test is required. Chronic or progressive conditions may need ongoing monitoring through the use of lab tests. Conditions that worsen and improve may also need frequent monitoring. Certain tests may be repeated to obtain a series of results, or tests may need to be repeated to confirm or disprove results. Timing and frequency of lab tests may vary if they are performed for professional or legal reasons.
How should I get ready for the test?
There is no preparation needed for this test.
How is the test done?
Fluid samples from your nose, throat, or mouth may be collected for this test. Caregivers should do this test as soon as possible if you begin to have signs or symptoms of swine flu.
A nasopharyngeal swab, aspirate, or wash is done to collect cell samples from the upper part of your nose and throat. For a nasopharyngeal swab, you will be asked to tilt your head back. The person doing the test will use a special kind of swab and insert it into one of your nostrils. The swab will be rotated gently and then remain still for a few seconds before it is removed. This is to allow the swab to collect a large enough sample to be tested. This process will be repeated in the second nostril. For an aspirate or wash, the healthcare worker will use a syringe to push a small amount of sterile saline into your nose, then either apply gentle suction (for the aspirate) or use gravity to collect the resulting fluid (saline and mucous) into a cup. The sample is then sent to the lab for testing.
How will the test feel?
The amount of discomfort you feel will depend on many factors, including your sensitivity to pain. Communicate how you are feeling with the person doing the test. Inform the person doing the test if you feel that you cannot continue with the test.
During a nasopharyngeal swab, aspirate, or wash, you may feel slight discomfort when the swab or fluid enters into the nostrils. You may gag or cough during the procedure.
What should I do after the test?
There are no special instructions to follow after this test.
What are the risks?
Nasopharyngeal cells: Ask the healthcare worker to explain the risks of this procedure to you before it is performed.
What are normal results for this test?
Laboratory test results may vary depending on your age, gender, health history, the method used for the test, and many other factors. If your results are different from the results suggested below, this may not mean that you have a disease. Contact your healthcare worker if you have any questions. The following is considered to be a normal result for this test:
- Adults and Children: Negative 
What follow up should I do after this test?
Ask your healthcare worker how you will be informed of the test results. You may be asked to call for results, schedule an appointment to discuss results, or notified of results by mail. Follow up care varies depending on many factors related to your test. Sometimes there is no follow up after you have been notified of test results. At other times follow up may be suggested or necessary. Some examples of follow up care include changes to medication or treatment plans, referral to a specialist, more or less frequent monitoring, and additional tests or procedures. Talk with your healthcare worker about any concerns or questions you have regarding follow up care or instructions.
Where can I get more information?
- Centers for Disease Control - www.cdc.gov
 Centers for Disease Control and Prevention: Interim Guidance on Specimen Collection, Processing, and Testing for Patients with Suspected Swine-Origin Influenza A (H1N1) Virus Infection. Centers for Disease Control and Prevention. Atlanta, GA. 2009. Available from URL: http://www.cdc.gov/swineflu/specimencollection.htm. As accessed 2009-04-29.
Last Updated: 11/4/2014