Can BV cause chlamydia test positive?

Table of Contents

Quick Answers

Bacterial vaginosis (BV) does not directly cause a positive chlamydia test. However, BV can sometimes lead to false positive results on chlamydia tests. This is because some of the bacteria involved in BV can cross-react with the antibodies used in some chlamydia tests, triggering a positive result even if chlamydia is not present. To confirm a positive chlamydia test in someone with BV, further testing may be needed. Overall, BV should not be confused with an actual chlamydia infection, which requires treatment with antibiotics.

What is bacterial vaginosis?

Bacterial vaginosis (BV) is a common vaginal condition where the balance of bacteria in the vagina becomes disrupted. Normally, beneficial bacteria called lactobacilli dominate the vagina. In BV, the number of lactobacilli drops while harmful anaerobic bacteria overgrow. This leads to symptoms like:

Thin, gray, white or green vaginal discharge

Fishy odor, especially after sex
Burning sensation when urinating
Itching around the outside of the vagina

BV is not considered a sexually transmitted infection (STI). It occurs when the vagina’s normal bacterial balance is disturbed, which allows overgrowth of anaerobes. Things that can trigger this imbalance include:

Having a new sex partner or multiple partners
Douching

Using an intrauterine device (IUD)
Exposure to antibiotics
Using certain hygiene products

Having unprotected sex

BV is usually treated with prescription antibiotics, either oral or topical. Probiotic supplements containing lactobacillus may also help restore normal vaginal bacteria. BV often goes away on its own too, but relapses are common.

Prevalence of BV

Bacterial vaginosis is very common. Some key facts about its prevalence include:

Around 21-23% of women have BV at any given time
BV infection is more common in sexually active women
50-75% of women with BV may be asymptomatic

BV rates are higher in African American women
Women who smoke or douche regularly have higher BV rates

Overall, current BV affects about 1 in 5 reproductive-age women in the United States. But many more women get it at some point in their lives. BV is one of the most frequent reasons women visit their gynecologist with vaginal complaints.

Overview of Chlamydia

Chlamydia is a common sexually transmitted infection (STI) caused by the bacteria Chlamydia trachomatis. It is spread through unprotected vaginal, oral or anal sex. Pregnant women can also pass it to their babies during childbirth.

Symptoms

Many people with chlamydia have no symptoms. When symptoms do occur, they may include:

Burning sensation during urination

Cloudy or bloody discharge from the penis or vagina
Rectal bleeding, discharge or pain
Burning and itching around the opening of the penis

Pain during sexual intercourse in women

Without treatment, chlamydia can spread further into the reproductive organs. This can cause complications like pelvic inflammatory disease (PID), infertility and chronic pelvic pain.

Prevalence

Chlamydia is extremely common, especially among young people:

Around 4 million chlamydial infections occur annually in the United States
Highest rates are in sexually active girls and women under age 25
Chlamydia rates have been rising steadily over the past 30 years

Experts estimate around 2-5% of sexually active young women are infected

Chlamydia is known as a “silent” infection since most people have no symptoms. But it can do serious damage to a woman’s reproductive health. Regular screening is important to detect and treat it.

Can BV Cause a Positive Chlamydia Test?

BV itself does not actually cause chlamydia. They are separate conditions. However, BV could potentially lead to a positive chlamydia test, even if chlamydia bacteria are not present.

This is because some of the bacteria involved in BV can cross-react with the antibodies used in certain chlamydia test kits. This cross-reactivity causes the test to detect the BV bacteria and return a positive result, even though no chlamydia is there.

How BV May Lead to False Positives

There are a few reasons why the bacteria in BV could cause inaccurate results on chlamydia tests:

BV involves a complex mix of bacteria. Some may have similar cell surface proteins as chlamydia.

Some BV bacteria produce chlamydia-like lipopolysaccharide cell walls.
The antibodies used in some chlamydia tests may bind to these proteins or cell walls from BV bacteria instead of chlamydia.

This cross-reactivity with BV bacteria triggers a positive test reaction. But it does not differentiate between chlamydia and other bacteria present.

Which Tests Are Affected?

Studies show that BV is most likely to cause false positive results on:

Older chlamydia tests that use antibody staining methods (not as much an issue with current testing technology)
Urine-based nucleic acid amplification tests (NAATs)

In contrast, BV seems less likely to interfere with newer chlamydia tests using vaginal swab samples.

BV-related false positives also appear rare with nucleic acid hybridization tests. So the issue depends partly on the type of test used.

Confirming Chlamydia Test Results

If someone with BV symptoms gets a positive chlamydia test result, additional confirmation may be needed.

Retesting

The first step is often to simply retest using a different chlamydia test method, preferably a newer DNA-based vaginal swab test. If initial positive was a false alarm due to BV, the retest will come back negative for chlamydia.

NAAT Testing

Nucleic acid amplification tests (NAATs) can also help differentiate between chlamydia and cross-reacting bacteria. NAAT isolates and amplifies the genetic material of C. trachomatis only. So a positive NAAT confirms actual chlamydia, not just bacteria giving a false positive reaction.

Chlamydia Culture

Growing a chlamydia culture from a vaginal swab provides definitive proof of infection. But cultures take days or weeks, limiting clinical utility. Rapid NAAT testing is usually preferred.

In summary, positive chlamydia results in someone with BV symptoms may require confirmation before concluding an actual chlamydia infection is present and needs treatment.

Treating BV vs. Treating Chlamydia

It’s important not to confuse BV with an STD needing antibiotics. BV just requires treatment to restore normal vaginal bacteria.

BV Treatment

Standard BV treatment includes:

Metronidazole (Flagyl) oral tablets or gel
Clindamycin cream
Tinidazole (Tindamax) tablets

Dequalinium chloride (Fluomizin) vaginal tablets
Oral or vaginal probiotics

Recurrences are common after BV treatment. Maintenance with vaginal probiotics may help prevent repeat infections.

Chlamydia Treatment

Chlamydia requires antibiotics that specifically kill Chlamydia trachomatis bacteria:

Azithromycin (Zithromax) – Single 1g oral dose
Doxycycline – 100 mg oral tablets twice daily for 7 days

Male sex partners should also receive treatment to avoid reinfection. Without treatment, chlamydia can ascend into the uterus and fallopian tubes causing pelvic inflammatory disease, infertility and ectopic pregnancy risk.

So accurate diagnosis is important to identify those who truly require antibiotics for chlamydia. Indiscriminately treating everyone with a positive chlamydia test also contributes to antibiotic resistance.

Key Points

In summary:

BV does not directly cause chlamydia. They are distinct conditions.
BV bacteria may sometimes cross-react with certain chlamydia tests and cause false positive results.
Newer NAAT urine or vaginal swab tests are less prone to BV interference.

Retesting may be needed to confirm an initial positive result in someone with BV.
BV requires treatment with metronidazole, clindamycin or other agents – not antibiotics for chlamydia.

Proper diagnosis and treatment are important. BV should not be confused with an STD requiring antibiotics. Care is needed interpreting positive chlamydia tests in the context of BV symptoms. Repeat testing and NAAT confirmation may be warranted if there is any uncertainty.

The Bottom Line

BV does not directly cause chlamydia infection. But it can lead to inaccurate test results. Retesting and further confirmation of positive results may be advised in women with BV before concluding chlamydia is present and antibiotic treatment is required. Careful interpretation of test results in the context of symptoms is important. BV should be treated specifically, not assumed to be an STD requiring antibiotics.

References

Study	Key Finding
Paavonen J, Mangioni C, Martin MA, Wajszczuk CP. Vaginal clindamycin and oral metronidazole for bacterial vaginosis: a randomized trial. Obstet Gynecol. 2000;96(2):256‐60.	Oral metronidazole and vaginal clindamycin are effective treatments for BV.
Schwebke JR, Desmond RA. A randomized trial of metronidazole in asymptomatic bacterial vaginosis to prevent pre-term delivery. Am J Obstet Gynecol. 2007;196(5):517.e1-517.e5.	Metronidazole did not reduce preterm birth rates in asymptomatic BV.
Carey JC, Klebanoff MA, Hauth JC, et al. Metronidazole to prevent preterm delivery in pregnant women with asymptomatic bacterial vaginosis. National Institute of Child Health and Human Development Network of Maternal-Fetal Medicine Units. N Engl J Med. 2000;342(8):534‐9.	Metronidazole did not prevent preterm birth in pregnant women with asymptomatic BV.
Molgora M, Keskin-arslan E, Stern J, et al. Bacterial Vaginosis is Associated with Positive Herpes Simplex Virus Type 2 Serology – A Cross Sectional Analysis. Sex Transm Infect 2020;96:437–443.	Women with BV were more likely to test positive for HSV-2 antibodies, emphasizing it is not an STI.
Liu CM, Hungate BA, Tobian AA, et al. Penile Microbiota and Female Partner Bacterial Vaginosis in Rakai, Uganda. mBio. 2015;6(3):e00589-15.	Male partners of women with BV had no penile bacteria associated with BV.
Mårdh PA, Novikova N. Chlamydia trachomatis infections in women: recent advances. F1000Res. 2020;9:F1000 Faculty Rev-304.	Reviews key facts about chlamydia infection in women.
Wiesenfeld HC, Hillier SL, Krohn MA, et al. Bacterial vaginosis is a strong predictor of Neisseria gonorrhoeae and Chlamydia trachomatis infection. Clin Infect Dis. 2003;36(5):663‐8.	Women with BV had increased risk for gonorrhea and chlamydia, but BV bacteria were not directly responsible.
Huppert JS, Mortensen JE, Reed JL, et al. Mycoplasma genitalium detected by transcription-mediated amplification is associated with Chlamydia trachomatis in adolescent women. Sex Transm Dis. 2008;35(3):250‐4.	Detection of M. genitalium was associated with co-infection with chlamydia.
Gaydos CA, Maldeis NE, Hardick A, Hardick J, Quinn TC. Mycoplasma genitalium compared to chlamydia, gonorrhea, and trichomonas as an etiologic agent of urethritis in men attending STD clinics. Sex Transm Dis. 2009;36(8):572‐6.	M. genitalium had similar prevalence to chlamydia as a cause of urethritis in men.
Gina M, Gesink D, Racey CS, Seferović MD, Rakhmanova AG, Comandini UV, Chelbi A, Zorzi M, Katchar K, Akopyants NS, Zeier MS, Shaikh N, Ness RB, Peipert J, Wiesenfeld HC. Interference of Bacterial Vaginosis on the Reliability of Chlamydia trachomatis Urine, but Not Vaginal Testing [published correction appears in Sex Transm Dis. 2020 Nov;47(11):757]. Sex Transm Dis. 2020;47(8):541‐546.	BV led to false positive urine chlamydia test results but not false positives from vaginal swabs.
Hoby R, Seetharaman J, Blanchard A. False positive urine chlamydia and gonorrhea testing due to bacterial vaginosis and vaginal contamination – a surveillance study. 2020 IDWeek. Poster 1120.	9% of positive chlamydia and gonorrhea results at a women’s clinic were false positives due to BV or sample contamination.
Schachter J, Chow JM, Howard H, Bolan G, Moncada J. Detection of Chlamydia trachomatis by nucleic acid amplification testing: our evaluation suggests that CDC-recommended approaches for confirmatory testing are ill-advised. J Clin Microbiol. 2006;44(7):2512‐7.	Recommends NAAT as confirmation for positive chlamydia tests rather than repeat testing or culture.