Oxalate, Glycolate, and Glycerate

Measurement of oxalate in urine is important for the diagnosis of primary hyperoxaluria (OMIM® 259900 and 260000) and the secondary forms resulting from excessive intake or abnormal intestinal absorption of oxalate [Von Schnakenburg and Latta (Physician’s guide to the laboratory diagnosis of metabolic diseases. Springer Berlin Heidelberg, 2003), Williams (Kidney Int 13(5):410–417, 1978)]. Determination of glycolic acid is essential for the diagnosis of primary hyperoxaluria type I (PH-I), caused by low or absent activity of the liver-specific peroxisomal alanine:glyoxylate aminotransferase. In addition, to estimate the risk of stone formation in calcium oxalate urolithiasis and nephrocalcinosis, simultaneous determination not only of calcium, but also of citrate (a potent inhibitor of calcium oxalate and calcium phosphate crystallization) and other constituents (electrolytes, phosphate, and sulfate) are required to calculate the urinary calcium saturation [Leumann et al. (Nephrol Dial Transplant 10 Suppl 8:14–16, 1995)]. Primary hyperoxaluria type II (PH-II) is caused by low or absent activity of D-glycerate dehydrogenase and hydroxypyruvate reductase activity, leading to elevated urinary excretion of both oxalate and L-glycerate [Von Schnakenburg and Latta (Physician’s guide to the laboratory diagnosis of metabolic diseases. Springer Berlin Heidelberg, 2003)]. High-pressure ion chromatography (HPIC) is the method of choice for the quantification of oxalic acid, glycolic acid and glyceric acid, often also referred to by their conjugated base names oxalate, glycolate, and glycerate [Hoppe et al. (Kidney Int 53(5):1348–1352, 1998), Politi et al. (Clin Chim Acta 184(2):155–165, 1989)]. In addition, preservation and storage of the liquid samples may influence the stability of oxalate and glycolate. The use of urinary filter spots is a practical alternative approach for the collection and safe transport of samples to be analyzed for many metabolic disorders [Blau et al. (Clin Chem 44(7):1554–1556, 1998)].