Evaluation of the interference by homogentisic acid and other organic acids on the enzymatic and Jaff method creatinine assay

摘要

Several inborn errors of metabolism, such as alkaptonuria, glutaric acidemia type I, methylmalonic acidemia and pro-pionic acidemia are associated with the excretion of high concentrations of specific organic acids. These organic acids could interfere with the determination of creatinine in urine. Loken et al. recently reported that the enzymatic measurement of urinary creatinine is unsuited in patients with alkaptonuria because the assay is negatively influenced by homogentisic acid (HGA) (1). The possible interference by other organic acids that can be present at high concentrations has to our knowledge not been studied. Interference of urinary creatinine measurement influences the reported results of all parameters that are normalized to urinary creatinine. Our aim was to investigate whether high concentrations of HGA and three other organic acids that can be present at concentrations of > 100 mmol/L [methylmalonic acid (MMA), 3-hydroxpro-pionic acid (PA), and glutaric acid (GA)] (2) interfere with the enzymatic assay and the Jaffe method.