Use of isotope dilution--mass spectrometry for accuracy control of different routine methods used in clinical chemistry.

Serum from patients was pooled, filtered, dispensed and frozen. The serum pool obtained was used for accuracy control in twenty-one participating laboratories in the Stockholm area. Mean values (state of art values) were obtained for creatinine, cholesterol, glucose, urea and uric acid. These values were compared with values obtained with highly accurate reference methods, based on isotope dilution--mass fragmentography. The most marked difference was found in the case of determination of creatinine. It is suggested that immediate access to such a well-defined human serum might decrease the need for conventional interlaboratory control programmes.