Application of analytical performance specifications for urine test strip methods: Importance of reflectance signals

Introduction: Urinalysis is essential for diagnosing kidney-related medical conditions. Urine test strip analysis serves as an initial and efficient screening method for reflex testing with accurate quantitative methods. Materials and Methods: Freshly voided urines (n = 206) were analysed using two urine test strip brands on UC-MAX (Menarini) and cobas u 601 (Roche Diagnostics) instruments. Ordinal scale categories and reflectance signals (if available) were both used for the comparison with reference quantitative methods for glucose, proteins and albumin (cobas 503). Samples were considered positive when glucose > 15 or ≥ 54 mg/dL, proteins ≥ 200 mg/L and albumin ≥ 10 mg/L. Optimized reflectance thresholds were calculated by ROC curve analysis. Analytical performance specifications (APS) for trueness of test strip were gathered from the EFLM guideline (FP_D, FN_G, FN_C). Results: Reflectance signals were significantly lower in urine samples considered positive by the reference method (p < 0.0001). Reflectance signals were also correlated with quantitative measurements, showing strong correlation (0.754 to 0.969). Only the use of optimized reflectance thresholds on cobas u 601 achieved at least the minimum EFLM APS (FP_D < 20%, FN_G < 50% and FN_C < 10%). Conclusion: The use of reflectance signals from urine test strips enhanced accuracy for glucose, proteins, and albumin measurement and may contribute to improve diagnosis of diverse kidney-related conditions.