How to Handle a False Positive STD Test: Confirmation Before Action

A false positive STD test is uncommon but does happen, and the way you handle it matters. Acting on a false positive can mean unnecessary antibiotics, unnecessary partner notification, and significant emotional distress. The correct approach is confirmation before any of that happens.

Quick answer: If your STD test comes back positive and you have no symptoms and no clear exposure, request a confirmatory test before notifying partners or starting treatment. False positives are rare but occur most commonly with herpes IgG (particularly low positive values), syphilis RPR/VDRL in certain conditions, and NAAT tests for chlamydia/gonorrhea due to contamination. Same-day testing for confirmatory results available in Los Angeles, Houston, New York City, Chicago, and Miami.

Which Tests Have the Highest False Positive Rates

Herpes IgG: The most common source of clinically significant false positives. The HSV-2 IgG test has a specificity of approximately 96–98%, meaning 2–4% of negative people will test positive. In low-prevalence populations, this produces a meaningful false positive rate. Low-positive results (index values between 1.1 and 3.5) are particularly unreliable — a significant proportion represent false positives. If you receive a low-positive HSV-2 IgG result, confirmatory testing with the Western blot (the gold standard for herpes serology, performed at the University of Washington) is recommended before acting on the result.

Syphilis RPR/VDRL: Non-treponemal syphilis tests have a biologic false positive rate in certain conditions: pregnancy, autoimmune diseases (particularly lupus), viral infections, IV drug use, and advanced age. A positive RPR or VDRL should always be confirmed with a treponemal test (TPPA or FTA-ABS). A positive non-treponemal test with a negative treponemal test is a biologic false positive — syphilis is not present.

Chlamydia and gonorrhea NAAT: NAAT tests are highly specific (>99%), making false positives rare. When they occur, the most common cause is specimen contamination during collection or processing. If you have a positive chlamydia or gonorrhea result with no symptoms and no plausible exposure, a repeat test on a new specimen — preferably at a different lab — is the appropriate step before treatment.

How to Respond to a Potentially False Positive

Request the specific test name and index/titre value from your result. Ask your clinician what confirmatory test is available for that specific infection. Do not notify recent partners before confirmation if you have genuine reason to suspect a false positive (no symptoms, no exposure). Do not begin antibiotic treatment for chlamydia or gonorrhea based on a single positive result if confirmation is feasible and the delay is short.

For herpes specifically: do not make decisions about long-term suppressive therapy, partner disclosure, or relationship changes based on a low-positive IgG result without Western blot confirmation. The consequences of incorrectly believing you have herpes are significant and long-lasting.

When False Positive Is Less Likely

A false positive is less likely when: you have symptoms consistent with the infection, you have a plausible recent exposure, the index/titre value is strongly positive (not borderline), and the test is a 4th generation HIV Ag/Ab test (extremely high specificity). In these circumstances, treating empirically while awaiting confirmation is often the right clinical decision.

Frequently Asked Questions

My chlamydia test was positive but I have no symptoms. Could it be wrong?

Possibly, but chlamydia is asymptomatic in up to 75% of women and 50% of men. A positive NAAT result is more likely to represent a real asymptomatic infection than a false positive. If you have no plausible recent exposure and the result seems inconsistent, discuss with your clinician whether a repeat test on a new specimen is appropriate before starting treatment.

How do I get a herpes Western blot test?

The herpes Western blot is performed primarily through the University of Washington Virology Laboratory. You need a clinician to order it. Many sexual health clinicians are familiar with ordering it for low-positive IgG results; if yours is not, requesting a referral to a sexual health specialist or infectious disease physician is appropriate.

Related: How to Read Your STD Test Results · Herpes Myths · Syphilis Testing · Get tested today →