Interlaboratory bilirubin variability.

Stabilized liquid quality control sera, some with elevated bilirubin concentrations, were distributed to laboratories for total and conjugated (direct) bilirubin analyses. Interlaboratory variability was high; for example, results ranged from 10.9 to 24.0 mg/100 ml for a serum with a mean bilirubin concentration of 18.1 mg/100 ml. Coefficients of variation were typically 10% to 12% for total bilirubin ad approximately 24% for conjugated bilirubin analyses. It is believed that these stabilized sera, when used as quality control materials, can help reduce the unacceptably large interlaboratory variability found in this study.