The effects of pH, temperature and storage on urine oxalate

Efeitos do timol sobre os parâmetros urinários envolvidos na formação de cálculos

“…determinação da excreção urinária dos parâmetros envolvidos na litogênese. Está bem estabelecido que a adição de conservante ácido reduzindo o pH urinário para valores próximos de 1 ou 2 é necessária para correta determinação do OxU (3,8,11,15,18,23,24,28) . Considerando que diversos distúrbios metabólicos podem apresentar variação de acordo com dieta e outros fatores ambientais, podem ser necessárias duas ou até três amostras de urina de 24 h para determinação dos distúrbios metabólicos envolvidos na formação de cálculos, como a hipercalciúria, hiperuricosúria e hipocitratúria (13,22,27) .…”

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

“…In the case of chlorides dosage is not recommended the use of HCl as a preservative because the hydrochloric acid influence this test. Uric acid dosage that did not show good results with the use of acid preservative which would justify that there are many laboratory guides that advocates the use of sodium hydroxide (NaOH) or bicarbonate (Na 2 HCO 4 ) to keep ph = 8 in urine favoring best results in urinary uric acid dosage [7,17]. There are constant reports in the literature validating new parameters in the 24 h urine due to its important diagnostic and monitoring [7].…”

“…There are constant reports in the literature validating new parameters in the 24 h urine due to its important diagnostic and monitoring [7]. Some studies such as determination of oxalate, citric acid, uric acid and creatinine have been described by many authors and in accordance with the methods adopted dosing have greater accuracy when using a preservative concentration of acid in 20 ml/l of 6 mol/l HCl to oxalate and citric acid maintaining the pH= 3-4 [16,17].…”