Can Chlamydia Testing Ever Be Wrong?

In answering this question, it's important to be clear about which type of chlamydia test is being used. Both the Centers for Disease Control and Prevention (CDC) and the US Preventative Services Task Force (USPSTF) now recommend that nucleic acid amplification tests (NAATs) are used to diagnose chlamydia and also gonorrhea. The CDC has recommended this type of test since 2002.

Older testing technologies, including culture-based methods, are not as accurate and are also more complicated to perform. A proportion of infections may be missed by older tests.

The NAAT tests are very accurate, even if -- like any test -- false results can occasionally occur. If the test says that you do not have chlamydia, this result is accurate for around 99 in every 100 people.

On the other hand, if the test says that you do have chlamydia, this result is accurate for at least 90 people in every 100. In other words, a few people may be falsely diagnosed with chlamydia when they in fact have another infection or nothing at all.

Occasional false results may be due to mistakes in taking the specimen and running the test, or because of contamination in the laboratory environment.

If you have reason to think that a test result is inaccurate, a second test may provide reassurance. If both tests give the same result, it is almost certainly accurate.

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In addition, our Q&A experts sometimes address questions about chlamydia and diagnostic tests in our "Ask the Experts" forums. Here are some of those questions and our experts' responses:

  • False negative STD test?
    A few months ago I tested positive for Chlamydia. My boyfriend recently got tested and his test results came back negative. Is there a chance he doesn't have it? Or was the test a false negative?
  • STD and HIV Test Results
    I have been sick for over the past ten years with so many symptoms of HIV: rashes, night sweats, hot flashes, joint pains, nausea, groin pains, and I easily catch colds. But I always test negative for HIV.