Correlation of urine culture with urine microscopy, leucocyte esterase and dipstick nitrite in detection of urinary tract infection

Abstract

Background. Improving diagnostic testing for urinary tract infections (UTIs) is essential to minimize unnecessary antibiotic use, which contributes to the growing problem of antibiotic resistance. This study aimed to evaluate the correlation between urine culture and three commonly used screening methods (urine microscopy, leukocyte esterase, and dipstick nitrite) for detecting UTIs. Method. A prospective observational study was conducted to assess the correlation between urine culture results and urine microscopy, leukocyte esterase, and dipstick nitrite tests. Based on clinical history, findings, and laboratory results, along with inclusion and exclusion criteria, and with parental consent, 76 children were enrolled in the study. Urine samples were collected and tested using microscopy, dipstick leukocyte esterase, and nitrite methods. Results. Of the 76 urine samples examined, 38 were culture-positive and 38 were culture-negative. The pathogens isolated included E. coli (n = 31), Pseudomonas spp. (n = 4) and Klebsiella spp. (n = 3). The sensitivity, specificity, negative predictive value (NPV) and positive predictive value (PPV) of urine microscopy were 97.37%, 18.42%, 54.41%, and 97.5% respectively; those of the urine dipstick leucocyte esterase were 76.32%, 63.16%, 72.73% and 67.44% respectively. For urine dipstick nitrite testing, the sensitivity, specificity, NPV, and PPV were 39.47%, 100%, 100%, and 62.3%, respectively. When any of the three screening tests were considered positive, sensitivity and negative predictive value increased to 100%. A total of 100% may be attributable to the relatively small sample size. Nonetheless, using any one of the screening tests as an indicator significantly improved sensitivity compared to using individual tests alone. Conclusion. This study highlights the benefit of combining dipstick tests (leukocyte esterase and nitrite) with urine microscopy as effective screening tools for UTIs. Employing multiple tests reduces the likelihood of missing a diagnosis, which is critical given that delayed detection of UTIs can lead to complications such as renal scarring and, in severe cases, renal failure.