Diagnostic utility of urine gram stain versus urinalysis in asymptomatic bacteriuria among pregnant patients

Abstract

BACKGROUND: Urine culture remains to be gold standard in the diagnosis of asymptomatic bacteriuria (ASB) during pregnancy but its use is limited because it is not cost beneficial. In low resource settings, urine gram stain and urinalysis maybe utilized as a alternative to urine culture. OBJECTIVE: This study aimed to compare urine gram stain and urinalysis using urine culture as gold standard in the diagnosis of asymptomatic bacteriuria (ASB) among pregnant patients; determine the sensitivity, specificity, positive and negative predictive values as well as compare the likelihood ratios of both tests. METHODS: This was a cross-sectional study conducted from July to December 2016 involving 220 pregnant patients on initial prenatal visit at the OPD of WVSUMC laboratory. Sensitivity, specificity, positive predictive values, negative predictive values and accuracy were computed for both tests in relation to urine culture. To compare for the diagnostic test characteristics, areas under the curve were generated. McNemar's Test was used to compare the superiority of urine gram stain over urinalysis. The research proposal was reviewed nd approved by WVSU Unified Biomedical Research Ethics Review Board. RESULTS: In this study, the prevalence rate of ASB pregnant women was 7.7%. It was found that the urine gram stain is more sensitive (58.82%) in the diagnosis of bacteriuria in pregnant patients as compared to urinalysis (29.41%). Urinalysis however was highly specific (94.09%) compared to urine gram stain (77.83%) in detecting ASB. The likelihood ratios of both tests were equally similar in detecting ASB. Comparing the relative sensitivity of both tests it was found out that urine gram stain had a significantly higher sensitivity than urinalysis (p=0.03). Urine gram stain was more sensitive but less specific than urinalysis in detecting ASB in pregnant women. However, based on Area under the Curve (AUC), both tests were comparable in the detection of ASB (P=0.26). CONCLUSION: Urinalysis because of its high specificity remains to be a good diagnostic tool for ASB while urine gram stain due to its better sensitivity is more effective in detecting the presence of ASB especially in low resource settings. For patients with negative urinalysis, we recommend proceeding to urine gram stain instead of urine culture because of the 7.7% ASB prevalence.

Keywords: Asymptotic bacteriuria, pregnancy, urinalysis, urine Gram stain