Comparison of Gram-stained smears prepared from blind vaginal swabs with those obtained at speculum examination for the assessment of vaginal flora

Objective To determine whether Gram-stained smears obtained from blind vaginal swabs could be used reliably for the assessment of the vaginal flora.

Design A prospective, blind comparative study.

Setting The antenatal clinic of a district general hospital.

Participants Eighty-eight women examined and screened for the presence of bacterial vaginosis during their first antenatal clinic visit. Two smears were obtained for each woman, the first prepared from a vaginal swab taken blindly and the second at speculum examination. The smears were Gram-stained and classified according to the Nugent score: Grade 1 (normal), Grade 2 (intermediate), Grade 3 (bacterial vaginosis).

Results Eight of the 88 pregnant women were identified as having bacterial vaginosis on the basis of the smear taken at speculum examination, and these were correctly identified as having bacterial vaginosis by smears prepared from the blindly taken swab. This gives the blind vaginal swab technique for detecting bacterial vaginosis a sensitivity and specificity of 100% when compared with swabbing at speculum examination. The flora of two women were graded as intermediate, and of 75 as normal by both techniques. Only in three cases was there a disparity between the two techniques, a difference that was not statistically significant (kappa = 0.8546,95% CI 0.6945 to 1.0).

Conclusions Vaginal smears prepared from correctly taken blind vaginal swabs can be used to assess the vaginal flora and screen for bacterial vaginosis. This method could be used in epidemiological studies of bacterial vaginosis in the general population and for screening antenatal populations for abnormal vaginal flora.