Comparison of urine dipstick test with conventional urine culture in diagnosis of urinary tract infection.

OBJECTIVE To determine the sensitivity, specificity, Positive Predictive Value (PPV) and Negative Predictive Value (NPV) of Urine Nitrite (NIT) and Leukocyte Esterase (LE) test compared with urine culture for diagnosis of UTI. STUDY DESIGN Validation study. PLACE AND DURATION OF STUDY Department of Microbiology, Army Medical College, Rawalpindi, from January 2013 to December 2013. METHODOLOGY Three hundred fresh uncentrifuged urine samples with suspicion of UTI, were collected and tested for LE and NIT by using (COMBI-10SL, UK) strip. Nitrite was considered as positive if there was a change in color of dipstick from colorless towards pink within 60 seconds. Leukocyte esterase was considered as positive if there was a change in color from off-white towards purple within 2 minutes. Quantitative urine culture was performed by using the strips calibrated to deliver 0.02 ul of urine on Cystine Lactose Electrolyte Deficient (CLED) medium agar. All plates were incubated at 37°C and read after 24 and 48 hours. Culture was considered as gold standard to evaluate the performance of dipstick test. RESULTS Out of 300 samples, 136 were culture positive and 164 were culture negative. Out of 136 positive culture results, 103 were dipstick positive and 33 were negative. Sensitivity, specificity, positive predictive value and negative predictive value of both nitrite and leukocyte esterase were 75.74%, 68.90%, 66.66% and 77.40% respectively considering culture as gold standard. CONCLUSION Dipstick test for the detection of leukocyte esterase and nitrite in urine are sensitive and specific and can be used reliably for the detection of UTI in resource limited setup.