Routinely testing people for Hepatitis A virus (HAV) - when they don’t have clinical symptoms of infection or a history of exposure - raises the likelihood of false-positive results, investigators report.

Hepatitis A is most often caught when sanitation is poor, or when carriers are not careful about personal hygiene. A false-positive test result may mean that a person’s contacts undergo unnecessary treatment to prevent infection.

Dr. Z. F. Dembek, at the Connecticut Department of Public Health, and colleagues investigated cases that tested positive for HAV in Connecticut and Alaska.

They report their findings in the Morbidity and Mortality Weekly Report, put out by the Centers for Disease Control and Prevention.

In Connecticut, 127 positive test results were reported between 2002 and 2003, but only 108 of the patients had illness consistent with acute hepatitis A. Of the remaining 19 considered to be false-positives, 9 had no symptoms of any illness and 10 had clinical signs that were not consistent with hepatitis A.

In Alaska, there were 27 cases consistent with HAV between 2002 and 2004, as well as 10 apparent false positives. Of these 10, seven patients had elevated liver enzyme levels and the other three had no symptoms.

Most false-positives came from older adults without typical risk factors for infection. In fact, most who underwent retesting had negative results.

To improve the value of the HAV test, “clinicians should limit laboratory testing for acute HAV infection to persons with clinical findings typical of hepatitis A or to persons who have been exposed to settings where HAV transmission is suspected,” the team concludes.

Editorialists agree that using the HAV test “as a screening tool or as part of testing panels used in the workup of nonacute liver function abnormalities should be discouraged.”

They add that doctors making decisions about preventive treatment for people who’ve been in contact with someone who has tested positive for HAV, but isn’t sick, should seek additional information.

SOURCE: Morbidity and Mortality Weekly Report, May 13, 2005.