GLYCOLATE DETERMINATION DETECTS TYPE-I PRIMARY HYPEROXALURIA IN DIALYSIS PATIENTS

The detection of type I primary hyperoxaluria is based on the finding of exceedingly high oxalate excretion which is associated with increased glycolate excretion. The differential diagnosis of this disease may become a difficult task once end-stage renal disease (ESRD) and anuria have supervened. The various procedures thus far proposed to obviate this circumstance are complex, inaccurate or not reproducible. In this paper we propose the accurate liquid chromatographic determination of glycolate in blood and dialysate as a means to detect type I primary hyperoxaluria in patients on maintenance hemodialysis (RDT). The method is based on the enzymatic conversion of glycolate to glyoxylate coupled with α-keto acid derivitization with phenylhydrazine. The resulting phenylhydrazone is then resolved by high-performance liquid chromatograph (HPLC). With this method, plasma glycolate in 12 healthy controls was 7.8 ± 1.7 μmol/liter, almost twentyfold less than previously reported. Five dialysis patients with high serum oxalate, of whom four with primary hyperoxaluria and one with Crohn's disease and presumed enteric oxalate hyperabsorption, were checked by this method and compared to nine patients with oxalosis-unrelated ESRD. The patients with hyperoxalemia were also evaluated for their response to pyridoxine therapy. The measurement of glycolate in blood drawn prior to and at the end of the dialysis session as well as in the dialysate soundly discriminated the patients with type I hyperoxaluria from all the other dialysis patients. Glycolate measurement was shown to be much more powerful than oxalate in that patients with oxalosis-induced ESRD exhibited an almost two hundred and fiftyfold increase compared to the oxalosis-unrelated patients. There was no overlapping at all irrespective of timing and type of sampling. Glycolate measurement represented a valuable tool to distinguish Crohn's disease related from genetically induced hyperoxalemia and to assess reponsiveness to pyridoxine treatment.