College of American pathologists experience with the linearity surveys, 1987-1991.

The Instrumentation Resource Committee has offered a survey since 1988 to perform and evaluate linearity. The survey uses a serum-based material and satisfies federal regulations that require linearity evaluations in the clinical laboratory. Both statistical and empirical methods to determine linearity were developed for the survey. Participant results have shown a high rate of nonlinear methods that may be due to our inability to accurately determine linearity or may reflect the true state of clinical assays. The survey shortcomings and future projects are discussed.