Gonorrhea Test May Give False-Positive Results; Doctors Encouraged to Learn Patients' Sexual History

ALEXANDRIA, Va. -- Five women from Hawaii in long-term monogamous relationships tested falsely positive for gonorrhea in an 8-month period, according to a study in the March 15, 2004 issue of Clinical Infectious Diseases..

All of the women had been tested by the Roche COBAS AMPLICOR CT/NG test from the same laboratory. Three of the women were tested as part of a family planning examination, and two because of symptoms that were later diagnosed as a non-sexually transmitted disease (STD)-related condition called bacterial vaginosis. None of the women's sexual histories indicated that they were at high risk for contracting an STD.

However, the test, called a nucleic acid amplification test (NAAT) is not really at fault. Its specificity, or the rate at which it correctly identifies people as not having gonorrhea, is greater than 99 percent.

"One must realize that any test with a specificity less than 100 percent will have the potential for false positive results," said Dr. Alan Katz, lead author of the study. "We want doctors to understand the limitations of the test and be selective in who they screen." The potential for false positive results increases if the test is used to screen people from low-risk populations or those living in areas where gonorrhea rates are low. In most areas of the country, chlamydia is much more common than gonorrhea, so routine screening of sexually active women under 25 is appropriate. The proper use of screening tests is a key factor in minimizing false positive test results.

Even more importantly, doctors should obtain the sexual history of their patients in order to evaluate STD risk and allow for the correct interpretation of test results.

"I think every primary care physician should get a sexual history on every patient," said Katz. "A doctor who knows that his or her patient is in a long-term, monogamous relationship will question an unanticipated positive test for gonorrhea and can re-test, perhaps preventing unnecessary psychological distress to a patient who's not expecting bad news."

Katz believes that physicians should even include young adolescents when asking for sexual history, although many people would disagree.

"By asking about sex, there's a perception in some quarters that you condone it," he said. "Not a lot of 10- to 14-year-old kids are sexually active, but those that are, are at high risk for gonorrhea and chlamydia." Such questions may be embarrassing, both for the patient and for the doctor, but that's no excuse. "You can't allow your personal issues to compromise your medical care," he said.

Source: Infectious Diseases Society of America (IDSA)