title: Implications for the use of acid preservatives in 24-hour urine for measurements of high demand biochemical analytes in clinical laboratories.
abstract: BACKGROUND
  Evaluate the level of interference of biochemists dosages in the 24-hour urine using or not the 6 mol/l HCl acid in different concentrations and conditions and its implications in the most demanded analytes in clinical laboratory.
  
  
  METHODS
  Twenty-two volunteers collected three 24-hour urine in 3 conditions: with 5 ml/l and 20 ml/l of 6 mol/l HCl in the container, and without acid preservative. The samples collected without preservative were separated in aliquots and added 5 ml/l of 6 mol/l HCl after 24 h. Analytes, uric acid creatinine, urea, chlorides, glucose, magnesium, sodium, potassium, microalbumin, proteins, amylase, aldosterone, calcium, cortisol, phosphorus, citric acid, oxalate, and metanephrines, were determined.
  
  
  RESULTS
  Uric 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 5 ml/l after delivery and r=0.31, r=0.70 and r=0.48 without preservative acid when compared with the gold standard (with 20 ml/l of 6 mol/l HCl).
  
  
  CONCLUSIONS
  Glucose, 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 5 ml/l of 6 mol/l HCl added after 24 h.
authors.affiliation: Psychobiology Department of the Universidade Federal de São Paulo, UNIFESP, São Paulo, Brazil. marciaferes@psicobio.epm.br
authors.forename: Marcia C
authors.initials: MC
authors.lastname: Feres
authors.forename: Rolando
authors.initials: R
authors.lastname: Bini
authors.forename: Maria Cristina
authors.initials: MC
authors.lastname: De Martino
authors.forename: Simone P
authors.initials: SP
authors.lastname: Biagini
authors.forename: Altay Lino
authors.initials: AL
authors.lastname: de Sousa
authors.forename: Paulo G
authors.initials: PG
authors.lastname: Campana
authors.forename: Sergio
authors.initials: S
authors.lastname: Tufik
mesh_terms: D000143:Acids / Q000737:chemistry*; D006801:Humans; D007753:Laboratories; D016482:Urinalysis
chemical_list: D000143:Acids