Disappointing Dipstick Screening for Urinary Tract Infection in Hospital Inpatients

Abstract

Aim—To compare the performance of leucocyte esterase and nitrite dipstick tests with microscopic examination and culture offirst morning urines (n = 420) of hospital inpatients. Results—The sensitivity, specificity, and negative predictive value of the leucocyte esterase test for the cutoV of > 10 WBC/µl were 57%, 94%, and 68%, respectively. For > 5 WBC per high powerfield (HPF) these variables were 84%, 90%, and 93%. For >1 0 5 colony counts/ml, the sensitivity of the nitrite test was 27%, specificity 94%, and negative predictive value 87%. When either leucocyte esterase or nitrite positivity was accepted as a marker of urinary tract infection, the sensitivity was 78%, specificity 75%, and negative predictive value 94%, and there were 22% false negative results. Semiquantitative microscopic estimation of bacteria per HPF yielded 40% false positives. Conclusions—Leucocyte esterase and nitrite dipstick tests are not suitable for screening for urinary tract infections. (J Clin Pathol 1998;51:471‐472)