Urinary Dipsticks: Efficacy as Predictor of Urinary Tract Infections

Urinalysis and culture are the two most common investigations performed in a microbiology laboratory. Commercial Dipsticks which detect proteins and various enzymes may offer a rapid and inexpensive alternative to urinalysis and culture. An evaluation of the utility of urinary dipsticks (Multistix 10 SG) in predicting urinary tract infections (UTI) was undertaken. A total of 667 urine samples were evaluated from May to August 2012. Sensitivity, specificity, negative and positive predictive values were evaluated. The sensitivity for predicting UTI was low: 62% for leukocyte esterase and nitrite; 67% for leukocyte esterase and proteinuria while it was 74% for leukocyte esterase, nitrite and proteinuria, all three together. However, the negative predictive value (NPV) for UTI was better. NPV for UTI with leukocyte esterase and nitrite was 90.3%; for leukocyte esterase and proteinuria was 90.6% while it was 91.5 % for leukocyte esterase, nitrite and proteinuria together. The positive predictive value was very low. Urinary dipsticks therefore appear to be better tools for excluding UTIs and not for diagnosing UTI.