A-099 Assessment of Stability of Routine Clinical Biochemical Results in 24-h Urine Specimen Under Conditions Simulating Various Preanalytical Variables

Abstract

Abstract Background The preanalytical phase has long been recognized as a source of substantial variability for 24-h urine samples. Hence, we examined the stability of analyte concentrations of 14 clinical biochemistry parameters commonly requested in a 24-h urine sample. The effects of various preanalytical variables simulating preexamination processes of the testing process were assessed. Methods We aimed to examine the effect of time delay in sample processing (up to 7 days), storage temperature (at 4 °C and room temperature), storage container (24-h urine bag, styrofoam box), and the effect of addition of toluene as preservative. The effect of the variables on clinical biochemistry parameters (uric acid, calcium, amylase, LDH, total protein, urea nitrogen, magnesium, phophorus, glucose, creatinine, sodium, potassium, chloride, and micro-albumin) in 24-h urine samples were assessed. Results Most of the analytes (uric acid, calcium, amylase, total protein, urea nitrogen, magnesium, creatinine, sodium, chloride, and micro-albumin) showed values not significantly different (≤± 5%) from baseline after 7 days of storage regardless of the storage temperature or addition of preservative. Three analytes were stable ≤24-h: phosphorus and glucose were stable up to 24-h and potassium up to 4-h. The addition of toluene had significant positive interference with LDH measurements. Conclusion According to our results, major analytes (uric acid, calcium, amylase, total protein, urea nitrogen, magnesium, creatinine, sodium, chloride, and micro-albumin) were stable up to 7 days in ambient storage conditions and toluene as a preservative was not necessary. However, a few analytes (phosphate, glucose, and potassium) were much more unstable and allowed ≤24-h or ≤4-h of storage in ambient or refrigerated conditions.