EVALUATION OF THE EFFECT OF SAMPLE STORAGE ON RENAL FUNCTION TEST BIOMARKERS IN USMANU DANFODIYO UNIVERSITY TEACHING HOSPITAL SOKOTO, NORTH WEST NIGERIA

Abstract

Accurate measurement of serum urea and creatinine is essential for evaluating renal function, yet these biomarkers are highly susceptible to pre-analytical variations, particularly storage conditions and delays before analysis. This study investigated the stability of serum urea and creatinine under three commonly used storage conditions: room temperature (baseline), refrigeration at 2–8°C for 24 hours, and freezing at –20°C for 48 hours and 1 week. A total of 40 healthy male participants provided venous blood samples, which were processed to obtain serum for biochemical analysis. Baseline (fresh) measurements were recorded immediately, followed by repeat measurements after each storage interval. The findings revealed that room temperature storage caused progressive increases in urea and creatinine levels, indicating ongoing metabolic activity and degradation of sample integrity. Refrigeration produced significant reductions in both biomarkers after 24 hours, suggesting that cold storage slows but does not halt biochemical reactions. Freezing resulted in improved stability compared with refrigeration, yet both urea and creatinine showed measurable declines, particularly after one week. Overall, freezing preserved analytes better than refrigeration, but none of the storage conditions maintained complete stability over time. These results underscore the importance of timely sample processing and strict adherence to pre-analytical guidelines. Immediate analysis or proper freezing at very low temperatures is essential to ensure accurate renal function assessment and prevent misleading clinical interpretations.