Severity of bacterial vaginosis and the risk of sexually transmitted infection

OBJECTIVE: The purpose of this study was to determine whether the association between bacterial vaginosis (BV) and incident sexually transmitted infection (STI) varies with more extreme BV scores. STUDY DESIGN: We analyzed the data from 535 women who were enrolled in a randomized trial to promote dual method contraceptive use. Incident STI was defined as any case of Chlamydia trachomatis, Neisseria gonorrhoeae, Trichomonas vaginalis, or pelvic inflammatory disease. BV was defined by Gram stain (Nugent score). STI risk was estimated with the use of proportional hazards regression. RESULTS: Binary (0-6 vs 7-10) and 3-level (negative 0-3, intermediate 4-6, or BV 7-10) categorizations were not associated with time to STI; however, women with the highest Nugent scores (9-10) had a 2.1-fold increased risk of STI (95% confidence interval, 1.05-4.28), compared with women with normal flora. CONCLUSION: Nugent score >8 is associated with incident STI. More accurate classification of BV will allow clinicians to identify those women who are at greatest risk of STI.