SENSITIVITY AND SPECIFICITY OF NITRATE REDUCTASE AND LEUCOCYTES ESTERASE AS RAPID SCREENING TESTS FOR DIAGNOSIS URINARY TRACT INFECTIONS.

*Wegdan Elsir Ahmed Ebnoof1 Walid Ahmed Hamid Eldaif2

*Wegdan Elsir Ahmed Ebnoof1 Walid Ahmed Hamid Eldaif2 1B.Sc. Medical Microbiology, Department of Medical Microbiology, Faculty of Medical Laboratory Sciences, Al Neelain University, B.O Box 12702 Postal Code 11121 Khartoum-Sudan 2B.Sc. M.Sc. Ph.D. Medical Microbiology, Department of Medical Microbiology, Faculty of Medical Laboratory Sciences, Al Neelain University, B.O Box 12702 Postal Code 11121 Khartoum-Sudan

Abstract

BACKGROUND: Urine analysis particularly leukocyte esterase & nitrate reductase tests are often used to determine whether a culture will be performed or treatment is needed. This study was conducted to assess the usefulness of leukocyte esterase, nitrate reductase and quantitative microscopic urine wet mount examination in rapidly diagnosing urinary tract infections (UTI).

METHODS: Ninety nine urine samples were collected from adult patients presenting to Asia Center, from March to May2010. The samples were tested by culture on Cysteine Lactose Electrolyte Deficient (CLED) medium. Microscopic examination of urine for significant pyuria, leucocyte esterase test (LET) and nitrite test (NT) were also performed. Culture was used as gold standard to evaluate the performance of direct microscopy and dipstick tests (1).

RESULTS: Nitrite test & leukocyte esterase test were found as specific for diagnosing UTI revealed 87.6% & 89.8% respectively. The sensitivity leukocytes esterase as simple diagnostic test for UTI was 50%, where as of nitrite test was 14.2%., The positive predictive value of a positive leukocyte esterase and Nitrite reductase tests were 66.6% and 8.03% respectively with high negative predictive value(91.02%,97,7%) respectively.

CONCLUSION: Urinary dipstick testing for UTI in the near patient setting is a valuable resource to screen out negative urine specimens at the point of care. Negative result for one of test has a sufficient predictive value to exclude disease, and when both test results are positive there is sufficient evidence to rule in infection.