Validity of pyuria and bacteriuria (detected by Gram-stain) in predicting positive urine culture in asymptomatic female children

Abstract

AbstractBackground & Objectives: Early diagnosis and treatment of urinary tract infections is a cost effective tool in preventing harmful complications in asymptomatic children. The present study assess the validity of two simple and cost saving parameters, namely pyuria determined by general urinalysis and bacteriuria (detected by Gram-stain), in predicting urinary tract infection (established by positive urine culture).Methods: A total of 600 healthy females children less than seven years of age were included in this study. Urine was collected by clean-catch technique. Fresh uncentrifuged urine specimens were examined for pyuria, while Gram-stained specimens were used to detect bacteriuria. Bacterial cultures were set on agar plates. A bacterial colony count of 105/ml of urine was considered as an evidence of significant bacteriuria and established the diagnosis of UTI.Results: The rate of positive urine culture tends to increase with the increasing number of pus cells detected by urinalysis. It also shows a significant positive trend with bacteriuria detected by Gram-stain. Pyuria at cut-off value of  10 pus cells/mm3 of urine provides the best working parameter for validity giving a positive predicting value (PPV) of 92.3% and a negative predicting value (NPV) of 94.2%. Bacteriuria (detected by Gram stain) at cut-off value of  3 bacteria/HPF provides the best working parameter for validity giving a positive predictive value of 85.7% and negative predictive value of 94.1%. Parallel combination of the two criteria is associated with 100% sensitivity and 100% negative predictive value. On the other hand, serial combination of both criteria is associated with 100% specificity and 100% positive predictive value.Conclusion: It is recommended to use both significant pyuria and bacteriuria (detected by Gram-stain) in parallel combination as a screening tool for asymptomatic UTI since their joint sensitivity is 100% in addition to being cheep and easy to perform.Key words: Asymptomatic UTI, pyuria, bacteriuria.