Comparison ofMethodsforDiagnosing Bacterial Vaginosis among Pregnant Women

Thediagnosis ofbacterial vaginosis isusually based on clinical criteria including homogeneous vaginal discharge, an elevated vaginal pH,thepresenceofclue cells, andan amineodor. Wehaveevaluated thevaginal flora andclinical signs for593pregnant women. Gardnerella vaginalis, Bacteroides spp.,andMycoplasma hominis were isolated more frequently among women withclinical signs than among those without clinical signs ofbacterial vaginosis inmultivariable analyses thatcontrolled forother bacteria. Todetermine thelaboratory methodthatbestpredicted bacterial vaginosis, we calculated thesensitivity, specificity, andpredictive value of positive andnegative tests forGram-stained vaginal smears,gas-liquid chromatography ofvaginal fluid, and G.vaginalis cultures compared withclinical signs. G.vaginalis culture was sensitive (92%)andbothgas-liquid chromatography (78%)andGram-stained vaginal smears (62%)were moderately sensitive inidentifying women withthree ofthefourclinical signs ofbacterial vaginosis. However, theGram-stained vaginal smear (95%) was more specific thanG.vaginalis culture (69%) orgas-liquid chromatography (81%). Thepredictive value ofa positive test was alsohigher fortheGramstaining (76%)thanforG.vaginalis culture (41%)or gas-liquid chromatography (48%). Bacterial vaginosis (nonspecific vaginitis) was recognized as a vaginal syndrome over 30years ago byGardner and Duke(9). Theyassociated bacterial vaginosis withtheisolation ofHaemophilus vaginalis, later briefly namedCorvnebacteriumr vaginale andcurrently namedGardnerella iaginalis (10). However, themicrobiology ofbacterial vaginosis iscomplex andinvolves organisms other than G. vaginalis. G. vaginalis can beisolated fromthevaginas of20to40%of women without bacterial vaginosis (1,4,6),andlarge quantities ofnotonly G. vaginalis butalsoanaerobic bacteria(16,18)andMycoplasmna hominis (13,14)can berecoveredfromwomen withbacterial vaginosis. Thediagnosis ofbacterial vaginosis hasusually been based on three or more ofthefollowing clinical signs ofthe vaginal discharge: a thinhomogeneous appearance, an elevated pH,anamineodorafter theaddition of10%KOH,and thepresenceofcluecells (vaginal epithelial cells studded withbacteria) (1,6,9).Fourother laboratory methods have beenusedtodiagnose bacterial vaginosis: culture ofvaginal fluid forG.vaginalis (9), gas-liquid chromatographic analysisofvaginal fluid forshort-chain fatty acids believed tobe products ofanaerobic bacterial growth(16,18),Gramstained vaginal smears readmicroscopically forbacterial morphotypes (5,19),andan assayforproline aminopeptidase(21). Eachlaboratory methodisbasedon theassumptionthatthevaginal flora ofwomen withbacterial vaginosis differs insome quantifiable way fromtheflora ofnormal women. Inprior reports, individual laboratory methods of diagnosing bacterial vaginosis havebeencomparedwith clinical signs (1,4,6,11,18M21). However, multiple laboratorymethods havenotbeencompared within asingle cohort ofwomen. Inthepresentstudy, we determined thevaginal flora of patients withbacterial vaginosis diagnosed byclinical signs, gas-liquid chromatography, and Gram-stained vaginal smears todocument thateachdiagnostic methodwas associated withsimilar vaginal flora. Thesensitivity, specificity,