Comparison of intermethod analytical variability of patient sera and commercial quality control sera

The intermethod analytical variability of 59 commercially available control sera was compared with that of patient sera. For this purpose, patient and control sera were assayed with respect to ten constituents (albumin, alkaline phosphatase, alpha-amylase, cholesterol, glucose, iron, lactate dehydrogenase, creatinine, protein, and urea), each with two analytical methods. Only 6 of the 59 control materials showed an intermethod analytical variability comparable to that of the patient sera for all of the determinations. The use of patient sera for the calibration of routine analytical methods is recommended.