G96(P) Are white cells in children’s urine diagnostic or a distraction, and does collection and culture method matter? new data from 4910 acutely unwell children

Abstract

AimsTo describe the relationship between urine white cell count (WCC) and the microbiological diagnosis of UTI in acutely unwell children, and explore the influence of culture and collection method.MethodsMulti-centre, prospective, cohort study of acutely unwell children aged 3 months-5 years presenting to UK primary care whose urine samples were collected by clean catch or nappy pad, and cultured by both a Central Laboratory (CL) using spiral-plating, and Local NHS Laboratories (LL) using standard practice. Positive and negative predictive values (PPV and NPV) of diagnosing UTI were calculated for WCC ≥100/mm3 and WCC ≤10/mm3 respectively, comparing laboratories and sampling methods.ResultsOf 4910 samples, 1.9% had UTI in the CL and 5.3% in the LL.Table 1 outlines the PPV of WCC ≥100/mm3 and NPV of WCC ≤10/mm3 for diagnosing UTI by laboratory culture and sampling method.Abstract G96(P) Table 1 CL culture LL culture All Samples Clean Catch Nappy Pad All Samples Clean Catch Nappy Pad PPV of WCC≥ 100/mm3 23.9 % [17.5–31.6%] 33.3 % [25.0–42.8%] 0 30.3 % [22.7–39.1%] 38.7 % [29.3–49.0%] 6.9 % [1.8–23.6%] NPV of WCC≤ 10/mm3 99.0 % [98.7–99.2%] 99.3 % [98.9–99.5%] 98.6 % [98.3–98.9%] 95.8 % [95.4–96.2%] 97.7 % [97.2–98.2%] 93.6 % [92.9–94.2%] ConclusionsLocal NHS Labs diagnose almost 3x more UTIs than a reference Central Laboratory. Many of these may be false positives.A WCC ≥100/mm3 poorly predicts UTI on culture in acutely unwell young children consulting in primary care.Despite WCC≤10/mm3 having a good NPV regardless of collection or culture method, 37 of the 92 positive CL cultures (40%) had WCC≤10/mm3.RecommendationWe propose a diagnostic algorithm selectively utilising spiral-plating culture methods to potentially minimise unnecessary treatment and investigation for 9000 children per year across England and Wales.