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Lab tests for herpes often give wrong results

Many labs in the US are using outdated blood tests for genital herpes that often give erroneous results, according to a new report.
/ Source: Reuters

Many labs in the US are using outdated blood tests for genital herpes that often give erroneous results, according to a new report.

“Genital herpes is the most prevalent sexually transmitted disease in the United States affecting about a third of the adult population,” Dr. Zane A. Brown told Reuters Health.

The biggest concern with herpes is that it can be transmitted to newborn infants with devastating results. “Unfortunately, only 10 percent of adults infected with the virus are aware of their infection and are therefore able to spread the infection to sexual partners and newborns infants,” Brown noted.

There are two types of herpes virus -- HSV-1, which is responsible for common 'cold sores,' and HSV-2, which causes genital herpes.

As part of its test proficiency program, the College of American Pathologists recently sent 172 participating laboratories a sample of blood that was positive for HSV-1 antibodies and negative for HSV-2 antibodies.

While virtually all of the laboratories accurately detected HSV-1 in the sample, more than half incorrectly reported that the sample was positive for HSV-2 antibodies, Dr. Brown and Dr. Rhoda Ashley Morrow report in the American Journal of Obstetrics and Gynecology.

Currently, only tests based on a protein called glycoprotein G have been proven effective in typing antibodies to HSV, Morrow and Brown from the University of Washington School of Medicine in Seattle note in their report.

Ninety-four of the laboratories reported the type of test they used for HSV-2 antibody detection. All 44 sites that used a glycoprotein G-based test accurately reported that the sample did not contain HSV-2 antibodies. Labs that used non-glycoprotein G-based assays, on the other hand, “demonstrated high false-positive rates (14 percent to 88 percent) for HSV-2 antibodies.”

Brown said the inaccurate tests “will continue being marketed until the companies voluntarily withdraw them from the market. This places the burden on the health care provider ordering the test to know which lab uses what test, which is beyond the scope of training and capability of most health care providers.”

If the spread of herpes is to be stopped, said the researcher, “it is critical that laboratories use the approved, accurate (type-specific) blood tests that have been readily available in the U.S. since 1999.”