August 29, 2005

Lab tests for herpes often give wrong results

By Megan Rauscher

NEW YORK (Reuters Health) - 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outdated blood tests for genital herpes that often give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 commented to Reuters

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

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."

SOURCE: American Journal of Obstetrics and Gynecology,
August 2005.