Establishing Reference Intervals for Biochemical Analytes in Spot (Random) Urine Samples

Introduction: Urine is a dynamic biological fluid influenced by physiological and environmental factors.Spot urine samples offer a convenient alternative to 24-hour collections for evaluating analytes, particularly through analyte-to-creatinine ratios.This study aimed to establish genderspecific reference intervals (RIs) for urinary analytes in a healthy South Indian population.Materials and methods: This cross-sectional study, conducted at a tertiary care hospital in Telangana, India, recruited 240 healthy adults (120 men and 120 women) aged 18-60 years.Fasting blood and morning spot urine samples were analyzed for urea, creatinine, sodium, potassium, chloride, phosphorus, uric acid, magnesium, glucose, and albumin using a Roche Cobas c501 analyzer.Reference intervals were derived using the 95th percentile method, and analytical precision was validated.Results: Men showed higher levels of urine creatinine, urea, uric acid, and sodium, while women exhibited higher levels of chloride and albumin.Key RIs included: creatinine (40.7-400.9mg/dL), urea (men: 486-3052 mg/dL; women: 264-2431 mg/dL), and sodium (49.1-276.9mmol/L).Calcium/creatinine and uric acid/creatinine ratios were higher in women, reflecting gender-based metabolic differences.Analytical precision demonstrated low intra-assay coefficients of variation (<5%), confirming reliability.Significant sex-specific patterns necessitate individualized RIs for better diagnostic accuracy. Conclusion:This study establishes sex-specific RIs for urinary analytes and their ratios in spot urine samples, offering a reliable diagnostic tool for assessing renal and metabolic health.Analytical precision enhances clinical utility, making these RIs valuable for routine laboratory practice in the Indian population.