Implications for the use of acid preservatives in 24-hour urine for measurements of high demand biochemical analytes in clinical laboratories

Abstract

BackgroundEvaluate the level of interference of biochemists dosages in the 24-hour urine using or not the 6mol/l HCl acid in different concentrations and conditions and its implications in the most demanded analytes in clinical laboratory. MethodsTwenty-two volunteers collected three 24-hour urine in 3 conditions: with 5ml/l and 20ml/l of 6mol/l HCl in the container, and without acid preservative. The samples collected without preservative were separated in aliquots and added 5ml/l of 6mol/l HCl after 24h. Analytes, uric acid creatinine, urea, chlorides, glucose, magnesium, sodium, potassium, microalbumin, proteins, amylase, aldosterone, calcium, cortisol, phosphorus, citric acid, oxalate, and metanephrines, were determined. ResultsUric acid, glucose, microalbumin, protein, amylase and aldosterone showed that %CV ranging from 16 to 57% in the presence of acid preservative. Analytes that need acid preservative cortisol, citric acid and oxalate showed %CV ranging from 6 to 27% with r=0.66, r=0.77, r=0.70 respectively provided 5ml/l after delivery and r=0.31, r=0.70 and r=0.48 without preservative acid when compared with the gold standard (with 20ml/l of 6mol/l HCl). ConclusionsGlucose, microalbumin, protein, amylase and aldosterone urinary did not show good performance in the presence of acid preservative. Analytes that need acid preservative showed variation acceptable in condition 5ml/l of 6mol/l HCl added after 24h.