Stability of mean values of organic analytes in lyophilized quality control serum. A study utilizing data from the Quality Assurance Service (QAS) Program of the College of American Pathologists.

The long-term stability of mean values of six organic analytes in 48 commercial pools of lyophilized chemistry quality control serum is evaluated. These pools, provided by five manufacturers, have been used by nine Regional Quality Control Programs participating in the College of American Pathologists Quality Assurance Service. Creatinine yielded stable mean values in 88% of the pools studied. Both albumin and urea nitrogen demonstrated manufacturer and method-related changes in mean values. Bilirubin, cholesterol, and uric acid changes in mean values were independent of control serum manufacturer, predominant in calibrator-standardized automated procedures, and were clustered by years.