Tests commonly used to diagnose oral and genital
herpes are often unreliable, missing some cases of
infection and, in others, identifying an infection
that does not exist, say researchers at the
University of Washington School of Medicine.
In nearly half of patients with commercial test
results indicating that they were infected with the
most common cause of recurrent genital herpes,
herpes simplex virus 2 (HSV-2), a subsequent test
showed that the initial diagnosis was incorrect, the
researchers report in a paper published today in the
journal Sexually Transmitted Diseases.
The high rate of false-positive HSV-2 tests was
particularly troubling, said Dr. Anna Wald, who led
“These tests aren’t as good as they ought to be,
given that they are used to diagnose someone with a
chronic, lifelong sexually transmitted disease.”
Wald directs UW’s Virology Research Clinic and is a
professor of medicine, epidemiology, and laboratory
The investigators examined results from FDA-approved
tests used to diagnose HSV-2 and herpes simplex
virus type 1 (HSV-1), the most common cause of cold
These tests, called enzyme-linked immunoassays,
detect the presence of antibodies to the herpes
simplex viruses in a person’s blood. When the
antibodies are detected, the test is positive,
meaning that the person is infected by the virus. No
detected antibodies indicates no infection.
To assess the tests’ reliability, the UW researchers
reviewed the charts of 864 patients from a private
sexually transmitted disease clinic in Portland,
Oregon, who had been tested for herpes simplex virus
antibodies with one of the commercially available
immunoassays and who then sought a follow-up
confirmation test developed in the UW laboratories.
This test, called the UW Western Blot is considered
a highly accurate, “gold standard” test.
For HSV-1, the researchers found that, among the 278
people whose immunoassay registered as positive, 255
were confirmed infected by blot test, suggesting
that a positive immunoassay result for HSV-1 is
However, the immunoassay missed about 30 percent of
those whose HSV-1 infection was positively
identified with the blot test.
More troubling were the antibody test results for
HSV-2. Of the 381 patients who tested positively,
only 50.7 percent were confirmed as infected with
the blot test.
“These findings indicate that if you didn’t have
signs and symptoms of genital herpes and were
diagnosed by an (immunoassay antibody) test alone
and had a low positive index value, there’s a 50-50
chance the test was wrong,” Wald said. “In that
case, you should get a confirmatory test.”
“We know that lab tests are not perfect, but this
margin of error for both HSV-1 and HSV-2 is not
acceptable. Clearly we need better tests,” Wald
Current guidelines recommend antibody tests for
HSV-1 or HSV-2 for people who have partners with
genital herpes, who have atypical symptoms that
might be genital herpes, or who have been diagnosed
with herpes by visual exam only. General screening
of people who have no symptoms is not recommended.
“People often request HSV tests when they are
concerned about their sexual health. People about to
start a new relationship want to know what they
bring to the bedroom, and since genital herpes is a
common STD, and often asymptomatic, it seems
reasonable to want to be tested for it,” Wald said.
Federal regulators have proposed limiting lab
testing to commercial tests approved by the U.S.
Food and Drug Administration – a change that Wald
“Many laboratories, especially academic
laboratories, have developed and validated their own
tests,” she said. “In case of testing for HSV,
limiting testing to FDA-approved tests will deny
patients access to these more reliable tests.”
Study co-authors include nurse practitioner Terri
Warren, in whose clinic the study was based, and Dr.
Keith Jerome, head of the UW Virology Division, in
whose lab the Western blot test is performed.
For more information
American Sexually Transmitted Diseases
Performance of Commercial Enzyme-Linked Immunoassays
for Diagnosis of Herpes Simplex Virus-1 and Herpes
Simplex Virus-2 Infection in a Clinical Setting.