Comparison of three spot proteinuria measurements for pediatric nephrotic syndrome: based on the International pediatric Nephrology Association 2022 Guidelines

Background Pediatric nephrotic syndrome (NS) requires routine proteinuria monitoring, which is costly and affects patients' quality of life. The gold-standard 24-h urine protein (UP) measurement is challenging in children, and first-morning urine collection requires specific conditions, making it difficult in outpatient settings. Studies have reported comparability of second or random morning urine sample to the first-morning specimen. This study aimed to compare outcomes of random morning proteinuria measurements to 24-h UP and the roles of the urinary protein creatinine ratio (UPCR) and dipstick tests in pediatric NS, based on International Pediatric Nephrology Association (IPNA) 2022 Guidelines.Method Twenty-four-hour and morning urine samples were collected from 92 pediatric NS patients. These were subjected to automated analyses for 24-h UP, UPCR, and semi-automated dipstick analysis. A blinded doctor performed manual dipstick analysis.Results UPCR had a stronger correlation with 24-h UP than with automated and manual urine dipstick tests. UPCR had the highest sensitivity and specificity for predicting no remission/relapse and high sensitivity but low specificity for complete remission. The optimal UPCR cutoff for remission was 0.44 mg/mg and for no remission/relapse was 2.08 mg/mg. Automated and manual dipstick tests demonstrated limited sensitivity but high specificity and similar AUC values for remission/relapse.Conclusion UPCR was sensitive and specific for diagnosing no remission/relapse and sensitive but not specific for detecting remission. Manual and automated urine dipstick tests were comparable for remission and no remission/relapse detection. This study supports the IPNA 2022 Guidelines, as 2 mg/mg was the optimal UPCR cutoff for no remission/relapse, while for remission the optimal cutoff was 0.4 mg/mg.