Diagnosis of Lower Genital Tract Infection in Pregnancy: Routine Midtrimester High Vaginal Swab Followed by Gram Staining, Seems to be the Best Strategy

Abstract

Background: Screening of lower genital tract infection (LGTI) in mid-trimester prevents preterm birth (PTB). There is no consensus on best screening methods for LGTI-symptoms, speculum findings, a point of care tests or high vaginal swab microscopy. Aim: To know diagnostic accuracy of screening of lower genital tract infection (LGTI) in midtrimester by clinical symptom/signs and point of care tests (viz Amsel’s criteria) as against the gold standard microscopic tests using gram stain. Settings and Design: Prospective observational study in a tertiary care hospital over two years. The study population included 228 antenatal women between 18th-24th weeks. Materials and Methods: Symptoms of vaginal discharge were noted. Speculum examination was performed on all, to detect the type of discharge. High vaginal swabs were collected, subjected to the point of care tests (Amsel’s criteria) as well as gram staining. Microscopy (Eg: Nugent’s criteria) was taken as the gold standard, to which other methods were compared. Results: Thirty women (13.5%) were symptomatic. Among 198 that were asymptomatic, 91(45.92%) had LGTI. Speculum examination showed discharge in 221 (96.9%), but gram staining showed LGTI in only 104 (45.61%), among whom 45 (19.7%) had partial Bacterial vaginosis (BV), 14(6.1%) had full BV, and 40(17.5%) had candidiasis. The commonest discharge was homogenous thin white, suggestive of BV but 51% among them had normal vaginal flora (NVF); whereas 27% of those labelled physiological discharge were positive for BV. The appearance of discharge and gram stain thus did not correlate well. Amsel’s criteria had poor diagnostic accuracy compared to Nugent’s, although negative predictive value were high. Conclusion: There is a high prevalence of LGTI, especially BV among asymptomatic pregnant women at mid-trimester, best detected with a routine high vaginal swab and gram staining rather than relying on symptoms/speculum findings/point of care tests. Such testing may guide appropriate treatment for reducing the risk of PTB.