Bacterial Vaginosis Linked to Increased STI Co-Infection, Finds National Study of 1.5 Million Women from Quest Diagnostics

Largest nationally representative study finds 12% of patients positive for bacterial vaginosis are infected with at least one STI, such as chlamydia or gonorrhea

SECAUCUS, N.J., July 30, 2026 /PRNewswire/ -- Women who test positive for bacterial vaginosis (BV) were over three times more likely to also test positive for one or more non-viral sexually transmitted infections (STIs) than women who test negative for BV, according to a new Health Trends® study from Quest Diagnostics (NYSE: DGX) and Hologic, Inc.

In the largest national study of its kind, scientists at Quest and Hologic analyzed deidentified aggregated laboratory data from over 1.5 million women across the United States who received molecular testing from Quest between 2022 and 2024. Over one-third of women tested (38.7%) were positive for BV. Of these, 12% were co-infected with at least one STI. The findings were published in O&G Open, a peer-reviewed companion journal to Obstetrics & Gynecology, the official publication of the American College of Obstetricians and Gynecologists (ACOG).

"BV is one of the most common health problems in women, and yet research in this area of women's healthcare is sadly lacking. Our new analysis provides compelling evidence that women with BV are at significant risk for STIs based on a uniquely large dataset reflecting the nation's heterogenous population," said co-author Damian P. Alagia III, MD, a board-certified obstetrician/gynecologist and Senior Medical Director, Women's Health, Quest Diagnostics. "STIs can lead to serious reproductive and other health complications when left undetected and untreated. We hope our new data inspires much-needed additional research on this clinical area while also reinforcing for clinicians and policy makers the value of a comprehensive diagnostic approach that considers STI testing for patients with BV."

Growing evidence suggests that changes in the vaginal microbiome may contribute not only to vaginitis, a common condition associated with inflammation, discomfort and infection, but also to increased susceptibility to other STIs, including HIV, chlamydia, gonorrhea and trichomonas.

Key findings:

• Among the more than 1.5 million women tested, 38.7% were positive for BV and 28.5% were positive for vulvovaginal candidiasis. Approximately 10.8% were positive for both.
• 12.0% of BV-positive women had at least one STI, compared to only 3.8% of BV-negative women.
• After adjusting for other factors, BV-positive status was strongly associated with increased odds of having:
  • Chlamydia trachomatis: 2.8 times higher odds.
  • Neisseria gonorrhoeae: 3.8 times higher odds.
  • Trichomonas vaginalis: 3.6 times higher odds.
  • Mycoplasma genitalium: 1.9 times higher odds.
• The presence of vulvovaginal candidiasis alone was not found to be associated with an increased risk of having an STI co-infection.

Nearly 30% of women in the U.S. are believed to experience BV at some point in their life. Guidelines from the Centers for Disease Control and Prevention (CDC) recommend that women with BV should be tested for STIs, which can present with similar symptoms, complicating diagnosis. Modern molecular diagnostics can allow for comprehensive assessment of vaginal infections from a single specimen, supporting timely detection and management of infections.

"This research confirms and expands on previous research on increased STI risk in women with BV, but with the advantage of a much larger data set from which to draw conclusions," said Elizabeth M. Marlowe, MS, PhD, Executive Director, Infectious Disease, Quest Diagnostics. "This large study underscores the value of comprehensive molecular testing when clinically indicated, enabling clinicians to detect coinfections from a single specimen, optimize patient management, and strengthen evidence-based care."

The study's strengths include its large, diverse and nationally representative sample size. The detailed analysis strengthens the evidence-based literature for reliable, impactful clinical guidelines to support the use of advanced molecular testing. The primary limitation to this retrospective study was that the data was provided by a single national laboratory, and that specific patient information like additional risk factors were not available.

In 2024, Quest introduced self-collection services for bacterial vaginitis and other common genital tract infections at its more than 2,000 patient service centers, for patients who prefer to self-collect a specimen, instead of collection by a healthcare provider.

About Quest Diagnostics
Quest Diagnostics works across healthcare to create a healthier world, one life at a time. We connect people, from clinicians to consumers, with laboratory insights that illuminate a path to better health. With a focus on delivering smarter, simpler testing, we help reveal new avenues to identify and treat disease, empower healthy behaviors and improve healthcare management. Quest Diagnostics serves half the physicians and hospitals in the United States and one in three American adults each year, and our nearly 60,000 employees work together to deliver diagnostic insights that inspire actions to transform lives. www.QuestDiagnostics.com

SOURCE Quest Diagnostics