A-359 Feasibility of urinalysis with reflex to urine culture in a large pediatric hospital system

Abstract Background Reflex testing in urinalysis can be a valuable tool to reduce: 1) the number of unnecessary urine cultures 2) the inappropriate use of antibiotics for asymptomatic bacteriuria and 3) healthcare costs. Developing a urinalysis with reflex to urine culture strategy in pediatrics involves several key steps which must be carefully evaluated prior to implementation to ensure the strategy is effective, avoids missing significant infections, and is tailored to specific needs of pediatric patients. Considerations in a pediatric population include patient age, proper urine specimen collection, and optimal cutoff criteria for pyuria and cultures to identify clinically significant urinary tract infections. These considerations were evaluated to determine whether a urinalysis with reflex to culture strategy could be employed at our large pediatric hospital system. Methods A retrospective review was conducted on samples with simultaneous urinalysis and urine culture tests between May 4, 2024 and December 30, 2024. The performance of urinalysis was evaluated using positive urine culture results at three different cutoffs, 1,000 CFU/mL, 10,000 CFU/mL, and 50,000 CFU/mL. A urinalysis result was interpreted as positive if any of the three components, nitrite, leukocyte esterase and white blood cells (WBC) were positive. Pyuria was defined as 10 WBC/HPF. Uropathogens included but were not limited to Escherichia coli, Enterococcus species, Enterobacterales, Staphylococcus species, Beta hemolytic Streptococcus species, Pseudomonas species, and Yeast. Results A total of 4,601 samples were selected for the study which included 885 (19.2%) catheter collections and 3,716 (80.8%) non-sterile collections (clean catch, voided, first morning, unspecified). The results are summarized in the table below. Using 1,000 CFU/mL as the positive culture cutoff, catheter collection had a false negative rate of 6.6%, which decreased to 2.4% with a cutoff of 10,000 CFU/mL. Higher false negative rates of 13.1% (1,000 CFU/mL) and 4.7% (10,000 CFU/mL) were observed with non-sterile collections. However, regardless of collection methods, there was no difference in the false negative rate using a cutoff of 50,000 CFU/mL. With a cutoff of 1,000 CFU/mL, catheter collection had a negative predictive value (NPV) of 91.5%, compared to 77% for non-sterile collection. Increasing the cutoff to 10,000 CFU/mL significantly increased the NPV for catheter collections to 96.9% and non-sterile collections to 91.8%. Conclusion Recent publications have indicated the most commonly used urine culture thresholds in children are 10,000 CFU/mL and 50,000 CFU/mL. By using 10,000 CFU/mL as the cutoff for catheter collection and 50,000 CFU/mL for non-sterile collections, our data indicates a high negative predictive value and a low false negative rate for urinalysis testing. Therefore, urinalysis is a reliable method to rule out urinary tract infections and may reduce the need for unnecessary urine cultures by implementing a urinalysis with reflex to urine culture test.