Case-Based Analysis of Pre-analytical and Analytical Non-Conformities in Urinary Protein Testing

Accurate quantification of urinary protein is fundamental for the diagnosis, monitoring, and management of kidney disease. Despite technological advances, both pre-analytical and analytical non-conformities in laboratory testing remain significant sources of misinterpretation that can adversely affect clinical decision-making. This report analyzes two such cases to highlight common but critical pitfalls in proteinuria assessment. We present two illustrative cases: the first involves a pediatric patient, where a pre-analytical non-conformity led to a significant overestimation of proteinuria severity. The second case describes an elderly diabetic patient where an analytical non-conformity resulted in a profound underestimation of albuminuria. In both instances, discrepancies between semi-quantitative and quantitative results were the critical clues that prompted investigation. These cases underscore that urinary protein results, while quantitative, are not infallible. Vigilant attention to pre-analytical procedures, strict adherence to analytical limits, and the integration of semi-quantitative results as a plausibility check are essential to prevent diagnostic non-conformities. Effective communication between clinicians and laboratory professionals is paramount to ensure that laboratory results accurately inform, rather than misdirect, clinical decision-making.