Spurious hyperphosphatemia in patients with dysglobulinemia.

Following the introduction of the ASTRA automated chemical analyzer to the Brooklyn VA Hospital, we identified 14 patients with normal renal function and marked hyperphosphatemia (9.1 +/- 3.1 mg/dl). Reanalysis of these samples by standard SMA-II autoanalyzer demonstrated normal phosphate concentration (3.5 +/- 0.7 mg/dl). All patients had a dysglobulinemic syndrome and further examination indicated that ASTRA reagents produced significant optical turbidity in these sera. We conclude that chemical analysis of inorganic phosphorus by methods which do not deproteinate sera prior to colorimetric analysis are subject to nephelometry in the presence of dysglobulinemic samples and may result in spurious hyperphosphatemia.