Diagnostic Value of Leukocyte esterase and Nitrite Tests for the Detection of Urinary TractInfection
Melody Omrani Nava1, Nazanin Mirzaei2, Vahid Ebrahimian3, Meysam Molaei4, Fatemeh Tohidnia4 and Mahdi Pursafar41Department of Infectious Disease, Tonekabon Branch, Islamic Azad University,Tonekabon, Iran. 2Department of Clinical Pathology, Tonekabon Branch, Islamic Azad University,Tonekabon, Iran. 3Laboratory Department of Ramsar Imam Sajad Hospital,Ramsar, Iran. 4Faculty of Medical Sciences,Tonekabon Branch, Islamic Azad University,Tonekabon, Iran.
Abstract: Urinary tract infection (UTI)is one of the most important diseases. The laboratory is essential in the diagnosis of UTI. The value of the nitrite and leukocyte esterase tests in detection of UTI has been proved in some studies in various countries.The goal of our study was to determine the utility of such tests in UTI in Ramsar (north of iran). This was a cross-sectional study of patients presenting to Ramsar hospital with dysuria,urgency,or urinary frequency on history, or suprapubic or costovertebral angle tenderness on examination. Patients who had taken antibiotics in the past 72 hours, had indwelling foley catheters, symptomatic vaginal discharge, immunodeficiencydisorders, or were unable to provide a reliable history were excluded. For these patients samples were sent to laboratory center of hospital in order to urine analysis (U/A) and urine culture (U/C).Then we checked leukocyte esterase and nitrite dipsticks and compared them with results of U/C.Sensitivity, specificity and predictive values were calculated. In this study, 420 patients were enrolled 68(68/420) of patients had positive U/C. When the presence of leukocyte esterase and nitrite were assessed , the sensitivity of dipstick testing for leukocyte esterase was72%, the specificity was84.7%, the positive predictive value(PPV) was47.57%,and the negative predictive value(NPV) was94%.The sensitivity, specificity,PPV and NPV were 79.4%,94.3%,72% and 96% respectively. For both of them PPV was 65.5% and NPV was 99%. Among 420 patents with suspected UTI, we determined the high specificity of dipstick testing for leukocyte esterase and nitrite. Our results suggest that a dipstick test result that is negative for both leukocyte esterase and nitrite can effectively exclude the diagnosis of UTI for patients with suspected UTI. The positive predictive value of 65.5% suggests, however, that the dipstick test is relative useful for identifying patients who meet the laboratory criteria for UTI.
Keywords: Urinary tract infection; Leukocyte esterase; Nitrite; Urine culture Back to TOC