Evaluation of various screening tests to detect asymptomatic bacteriuria in pregnant women.

To evaluate the diagnostic efficacy of various screening tests in detecting asymptomatic bacteriuria among pregnant women. Clean catch midstream urine specimens were collected from 630 consecutive pregnant women and processed. Forty-four (7.4%) of the urine samples were culture positive, with Escherichia coli as the predominant organism isolated (57.4%). The results of the four screening tests, viz., Gram's staining of uncentrifuged urine, pus cell count, nitrite test and leukocyte esterase (LE) test, were compared against urine culture. Gram's stain of the uncentrifuged urine was found to be the single most useful test with a sensitivity and negative predictive value (NPV) of 85.1% and 98.8%, respectively. Pus cell count was the least sensitive. Neither the nitrite test nor the LE test alone was sensitive enough with 74.4% and 61.7%, respectively. However, when either or both tests positive were considered, it increased the sensitivity and NPV comparable with Gram's staining results, with 82.9% and 98.8%, respectively. With the potential to be used as an office diagnostic procedure, the combined nitrite and LE dipstick test may provide an acceptable alternative.