What Is the Test for Swine Flu?

2009 H1N1 influenza is widespread in the U.S.

Originally called the "swine flu" because of its similarity to influenza common in pigs, the 2009 H1N1 virus has been found to have a different genetic composition than originally thought. First detected in the U.S. in April, 2009, H1N1 is now widespread in 48 states, according to the Center for Disease Control and Prevention (CDC). Symptoms may include "fever, cough, sore throat, runny or stuffy nose, body aches, headache, chills, and fatigue," and in some cases, vomiting, diarrhea, and respiratory problems. Physicians have several options in diagnosing 2009 H1N1 (See References 1).

Most Common Test

The most common tests for the flu in clinic settings are "rapid influenza diagnostic tests (RIDT)," and require a swab sample from the interior of the nose. Results generally take about 30 minutes. However, RIDT reliability in diagnosing 2009 H1N1 "ranges from 10% to 70%," according to the CDC.

Temporarily Authorized Tests

The FDA has "authorized the emergency use of the 'Swine Influenza Test Kit,'" which provides generally accurate diagnosis for 2009 H1N1. The test, which has not been cleared or approved by the FDA, requires a nasal or throat swab. Unless revoked earlier than anticipated, the FDA's emergency authorization will expire April 26, 2010, or when the Secretary of Health and Human Services determines the emergency has passed (See References 2).

Blood Tests

Other lab tests require blood samples and can accurately differentiate between H1N1 and other flu viruses, but results generally take several days.

Professional Evaluation

The CDC issued formal recommendations to health professionals encouraging them to reserve influenza diagnostic testing for certain cases, including "people who are hospitalized with suspected flu, and people such as pregnant women with weakened immune systems." The CDC emphasizes that if you have flu symptoms, test results will not change your treatment, except in cases with severe symptoms. You may be diagnosed with the flu without being tested, based on your health care provider's evaluation of your symptoms.

Identification

According to the CDC, if you have been diagnosed with the flu, you likely have 2009 H1N1 since "99% of circulating influenza viruses in the U.S." as of September 2009 are of this strain. Additional testing is unnecessary in most cases. 70% of instances requiring hospitalization and further testing is done for high-risk patients including people over 65 years of age, children under 5 years of age, pregnant women, and people with certain chronic medical conditions, according the the CDC.

References

• Center for Disease Control and Prevention
• Food and Drug Administration