Asymptomatic bacteriuria in women attending an antenatal clinic at a tertiary care centre

Abstract

Objective. To compare the diagnostic performance of urine microscopy, leucocyte esterase and nitrite dipstick tests and various combinations of these as screening tests for asymptomatic bacteriuria in pregnancy.

Methods. Pregnant women (N=800) attending an antenatal clinic were recruited at their first visit. Urine microscopy, culture and dipstick testing were performed on a random clean-catch midstream urine sample. A colony count of >10⁵ colony-forming units of a single organism per millilitre of urine was taken as significant. Dipstick results were read as positive according to the manufacturer’s instructions.

Results. A total of 800 eligible women were screened. The prevalence of asymptomatic bacteriuria as diagnosed by urine culture was 5.0% (n=40). Escherichia coli was the most prevalent uropathogen isolated by culture (60.0%). Neither urine microscopy nor the leucocyte test was found to be sufficiently sensitive to be used as a single screening test for asymptomatic bacteriuria in pregnant patients. The nitrite test alone had a sensitivity of 82.5% and a specificity of 99.9%. Combined dipstick testing had an improved sensitivity of 87.3% and a specificity of 96.2%. Addition of urine microscopy to combined dipstick testing increased the sensitivity to 95.0%, and the specificity became 92.4%.

Conclusion. Combined dipstick testing is a useful screening test for asymptomatic bacteriuria in pregnancy. Addition of urine microscopy to combined dipstick testing further improves its diagnostic performance.