Interlaboratory salicylate variability.

Nineteen patients with juvenile rheumatoid arthritis had salicylate concentration determination by 2 different methods in 2 laboratories. Differences in the results from these laboratories prompted testing at 4 laboratories with known samples of salicylates. Significant variation was shown between spectrofluorometric and Trinder methods. We feel that it is imperative that physicians and clinical pharmacists determine the reliability of salicylate determinations performed in their laboratories prior to making recommendations for changes in patients' drug regimens.