Screening for asymptomatic bacteriuria in pregnancy: urinalysis vs urine culture

Abstract

Background: Asymptomatic bacteriuria is common during pregnancy. Its average prevalence is 6%. It is an important risk factor for acute pyelonephritis, hypertension, preeclampsia, fetal wastage, low birthweight, and prematurity. This study was performed to determine the usefulness of urine microscopy as a substitute for doing a screening urine culture.

Methods: The medical records of all first trimester obstetric visits from 1984 to 1990 were reviewed at a major university. The results of 888 screening urinalyses were recorded and compared with those of subsequent urine cultures.

Results: Fifty-four cultures had growth of a single organism with a bacteria level of at least 1000 organisms per milliliter. In the prediction of a positive culture, the microscopic findings of five or more leukocytes per high-power field (HPF) showed a sensitivity of 94.4% and a specificity of 95.0%.

Conclusion: Physicians should test the urine of all prenatal patients at their first visit and send to the laboratory only those specimens with 5 or more leukocytes per HPF. Using this method, unnecessary screening urine cultures will be substantially reduced.