Asymptomatic bacteriuria in pregnancy: evaluation of reagent strips in comparison to microbiological culture

Screening for asymptomatic bacteriuria during pregnancy, the major risk factor for symptomatic urinary tract infection during pregnancy have been recommended. This cross sectional study was conducted to determine prevalence of asymptomatic bacteriuria in Ibadan and evaluate the diagnostic accuracy and relative cost effectiveness of dipstick tests for nitrite and leucocyte esterase in comparison to laboratory culture. Two hundred and five patients, presenting for their first antenatal visit at the University College Hospital, Ibadan, participated in the study. Urine samples obtained from the participants were subjected to two tests; reagent dipstick test for nitrite and leucocyte esterase and routine laboratory culture, which is the gold standard for diagnosis. Main outcome measures were sensitivity, specificity, positive and negative predictive values of the reagent dipstick tests as well as likelihood ratios. The prevalence of asymptomatic bacteriuria in pregnancy with routine laboratory culture and using combined leucocyte esterase and nitrite strip tests were 10.7% and 11.7% respectively. Compared with laboratory culture, combined strip tests had sensitivity, specificity and negative predictive values of 50%, 92.9% and 93.9% respectively, indicating a statistically significant lower level of accuracy (P < 0.05). The corresponding likelihood ratios for positive and negative strip tests (LR+ and LR-) were 7 and 0.5 respectively. The study concludes that combined Leucocyte esterase-nitrite dipstick test is not sufficiently sensitive and specific to be used for routine screening of bacteriuria in pregnancy in place of laboratory culture, though may be more cost effective in low resource settings.