Large Quest Diagnostics Study Links Bacterial Vaginosis to Triple the STI Risk

A study of more than 1.5 million women found that those with bacterial vaginosis (BV) were significantly more likely to also test positive for gonorrhea, chlamydia, trichomoniasis, or mycoplasma genitalium — reinforcing existing CDC guidance that BV patients should be screened for sexually transmitted infections.

In this article:

• What the study found
• Why researchers looked at this
• What made this study different
• Why this matters for BV patients

What the Study Found

Researchers at Quest Diagnostics analyzed lab data from more than 1.5 million women ages 15 and older who had a suspected vaginal condition. Nearly 39% tested positive for bacterial vaginosis and 29% for a yeast infection, with about 11% positive for both. Among women with BV, about 12% also had at least one STI, compared to fewer than 4% of women without BV.

After adjusting for other factors, having BV was linked to substantially higher odds across several STIs: about 3.8 times greater odds of gonorrhea, 2.8 times higher risk for chlamydia, 3.6 times higher odds for trichomoniasis, and 1.9 times higher risk for mycoplasma genitalium. Notably, a yeast infection alone was not associated with increased STI risk — the elevated risk was specific to BV.

Why Researchers Looked at This

BV affects close to 30% of women at some point in their lives, but according to senior researcher Dr. Damian Alagia, senior medical director of women's health at Quest Diagnostics, research into this common condition remains limited. The BV-STI connection specifically has been relatively unexplored despite BV's prevalence among sexually active women.

What Made This Study Different

Elizabeth Marlowe, executive director for infectious disease at Quest Diagnostics and a co-author, said the study's scale sets it apart from earlier research — a much larger dataset supporting more confident conclusions. The findings point to the value of comprehensive molecular testing that can detect coinfections from a single specimen, rather than testing for BV and STIs separately.

Why This Matters

For anyone diagnosed with BV, this study is a concrete reason to ask about STI testing at the same visit, even without additional symptoms. Since BV and several STIs can present similarly, a BV diagnosis alone may mask a coinfection that goes undetected without expanded testing. The findings also validate existing CDC guidance rather than introducing new recommendations, but the scale of this study adds real weight to a message clinicians may not always act on in day-to-day practice.

Conclusion

This is one of the largest studies to date connecting BV to STI risk, and it strengthens a clinical case that already existed: comprehensive testing at the point of BV diagnosis, rather than isolated single-condition testing, may catch infections that would otherwise be missed.

Sources

• Drugs.com/HealthDay, "Bacterial Vaginosis Tied To Tripled STI Risk, Major Study Finds" (August 4, 2026): drugs.com