BACKGROUND: Bacterial vaginosis is the most common vaginal infection among reproductive age women. It has been associated with preterm labor and emerged as a formidable disease entity associated with catastrophic sequelae especially in pregnant patients. Papanicolaou smear is the most successful screening test for cervical carcinoma in the history of medicine. Albeit being used by some clinicians as screening tool for bacterial vaginosis, it was not well established.

OBJECTIVE: To determine the diagnostic accuracy of papanicolaou smear in making the diagnosis of bacterial vaginosis in pregnant patients with the vaginal gram stain used as diagnostic standard.

METHODOLOGY: A total of 321 pregnant patients who consulted for prenatal care at the outpatient department of obstetrics and gynecology of the tertiary training hospital between November 2013 to-June 2014 were included in the study. Each patient had gram-stained vaginal smear and standard pap smear done consecutively. The sensitivity, specificity, positive predictive value, negative predictive value and the likelihood ratios of pap smear were determined.

RESULTS: The sensitivity of pap smear in determining the presence of bacterial vaginosis is 70.5%, its specificity of 93.6%, positive predictive value of 80.5%, negative predictive value of 89.3%. Likelihood ratio of a positive result is 10.9 and 0.3 for a negative result with diagnostic accuracy of 87.23%.

CONCLUSION: These results support the reliability of the pap smear in the diagnosis of bacterial vaginosis in asymptomatic pregnant patients. Since pap smear and gram stain have close diagnostic accuracy, duplication of the test could reasonably be avoided in most patients.