CDC suggests limiting use of IgM anti-HAV testing to curb false positive results

December 25, 2005 at 5:48 pm Leave a comment

Source: Infectious Disease News – June 2005

Physicians should only use IgM anti-HAV testing for people who meet the clinical criteria for hepatitis A infection.

Three investigations into the use of the immunoglobulin M (IgM) anti-hepatitis A virus (HAV) serologic test suggest that the positive tests reported recently are not representative of acute HAV infections.

“To improve the predictive value of a positive IgM anti-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,? CDC officials wrote in a recent Morbidity and Mortality Weekly Report (MMWR).

The investigations

The Connecticut Department of Public Health conducted telephone interviews with patients and health care providers concerning 127 positive IgM anti-HAV tests reported between January 2002 and April 2003 and found 108 had an illness consistent with the criteria for hepatitis A infection.

The 19 who did not meet the criteria for infection did not report recent exposure to a patient with hepatitis A and were either asymptomatic or did not have clinical signs of the illness.

Three of the 19 had elevated alanine aminotransferase (ALT) concentrations. In the four to 59 months leading up to the most recent test, three had a prior positive test. No one specific test brand or lot number was used for the tests, CDC officials said.

In Alaska, the Division of Public Health found that between 2002 and 2004, 27 reported cases of hepatitis A were consistent with the clinical definition of the infection and 10 were not.

Seven of the 10 had abnormal serum ALT concentrations, “indicating likely liver injury or disease,? CDC officials wrote. “However, six did not have an illness with acute onset and were considered unlikely to have hepatitis A.?

Of the 10, one patient was tested to examine the need for and response to vaccination. Another patient had tested positive in 2000.

The CDC examined data from its Sentinel Counties Study of viral hepatitis in the country for 2003 in response to requests from health departments for assistance in figuring out if those who were getting tested were truly infected. The study is a population-based surveillance in six U.S. counties; the six counties represent an age range and a racial ethnic composition similar to the entire country, CDC officials wrote.

One hundred forty people reported a positive IgM anti-HAV test in 2003, but 87 did not have criteria-consistent illness for hepatitis A infection. The CDC noted that those who did not have criteria-consistent illness were significantly older and female (P Test only when needed

“Test results indicating acute HAV infection among [people] who do not have clinical or epidemiologic features consistent with hepatitis A are a concern for state and local health departments because of the need to assess whether contacts need postexposure immunoprophylaxis,? the CDC said.

A lack of reason for testing on many of the people with false positive test results is one of the limitations of the study. Another limitation is that serum specimens without a criteria-consistent illness from Connecticut and Alaska were not available for further testing, while a limited number from the Sentinels Counties Study were available.

Still, the CDC said, “published guidelines for the workup of abnormal liver enzyme tests among asymptomatic patients do not include IgM anti-HAV testing.

“Health care providers should limit use of IgM anti-HAV testing to [people] with evidence of clinical hepatitis or to those who have had recent exposure to an HAV-infected person,? the CDC said.

“Persons who are IgM anti-HAV positive but who do not have illness consistent with the case definition for hepatitis A should not be reported to the CDC.?

For more information:
The CDC. Positive test results for acute hepatitis A virus infection among persons with no recent history of acute hepatitis — United States, 2002-2004. MMWR. 2005;54:453-456.

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Entry filed under: Hepatitis A, Metodos diagnosticos.

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