EXTRACTION OF GLYCERIC AND GLYCOLIC ACIDS FROM URINE WITH TETRAHYDROFURAN - UTILITY IN DETECTION OF PRIMARY HYPEROXALURIA

Primary hyperoxaluria (PH) is an autosomal recessive metabolic abnorma lity characterized by excessive oxalate excretion leading to nephrocal cinosis and progressive renal dysfunction. Type I primary hyperoxaluri a (PH I) results from a deficiency of alanine:glyoxylate aminotransfer ase, whereas type II disease has been traced to a deficiency of D-glyc erate dehydrogenase. The two syndromes are often distinguished on the basis of organic acids that are coexcreted with oxalate: glycolate and L-glycerate in type I and type II disease, respectively. Routine orga nic acid analysis with diethyl ether extraction followed by gas chroma tographic analysis failed to detect normal and increased concentration s of these diagnostic metabolites. Subsequent extraction of urine with tetrahydrofuran (THF), however, extracted 75% of added glycerate, 42% of added glycolate, and 75% of added ethylphosphonic acid (internal c alibrator). THF extraction was analytically sensitive enough to allow determination of normal excretion of glycolate (14-72 mu g/mg creatini ne) and glycerate (0-5 years, 12-177 mu g/mg creatinine and >5 years, 19-115 mu g/mg creatinine). Four of five patients with PH I and both p atients with type II disease were correctly identified. Thus, THF extr action is a convenient adjunct to routine organic acid analysis and fa cilitates the detection of PH.