A study of the accuracy and precision of clinical chemistry determinations in 170 Canadian laboratories.

Lyophilized samples of two serum pools, prepared commercially, were sent to 200 Canadian clinical chemistry laboratories for estimations of total cholesterol, sodium, chloride, glucose, nonprotein or urea nitrogen, total protein, and inorganic phosphorus. The purpose of this evaluation study was to determine if these laboratories, as a group, were performing satisfactorily, and to help individual laboratories to evaluate their performances and detect gross errors in their results. Values were reported from 170 laboratories. A summary of the complete data is presented in the form of tables, scatter diagrams, and frequency charts. It was found that there was a lack of accuracy and precision in many laboratories. Over 40% of the 3762 values reported fell outside of the allowable limits of errors and therefore were classified as unacceptable. These results indicated a need for improved performances in many of the participating laboratories.