Evaluation of gram stain of uncentrifuged urine as a screening method for diagnosis of urinary tract infections

Abstract

Significant portion of urine specimens submitted to clinical laboratories fail to grow any pathogen. Besides, there is a substantial delay of 24-48 hours in obtaining culture results. Hence, patients are usually treated by empirical antibiotic therapy. However there is a problem of emergence of drug resistance and also ineffective treatment when using empirical treatment. There have been conflicting reports about sensitivity and specificity of screening methods used to diagnose urinary tract infections (UTI). Aims: to evaluate gram stain of urine specimen as a screening test for urine culture and hence, as a guide to empiric antibiotic therapy. Materials and methods: Ninety eight urine specimens subjected to gram stain and culture. Gram stain findings were correlated with culture results. Gram stain was evaluated for its validity as a screening method by calculating sensitivity, specificity, positive predictive value and negative predictive value. Results: Sensitivity of gram stain was calculated to be 89.1%, specificity 86%, positive predictive value 85.4% and negative predictive value 89.6%. Conclusion: Gram stain of uncentrifuged urine is a very sensitive and specific screening test for diagnosis of UTI.