Clinical Chemistry
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Clinical Chemistry 20: 1416-1421, 1974;
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Clinical Chemistry, Vol 20, 1416-1421, Copyright © 1974 by the American Association for Clinical Chemistry

Warning Methods for Quality Control in Determinations of Serum Calcium

D. C. Hellbron 1, J. W. Eastman 1, and D. Kelly 1

1 Office of Information Systems and The Department of Clinical Pathology and Laboratory Medicine, University of California, San Francisco, Calif. 94143.

We have examined quantitative warning methods based on the measurement of controls (reference samples) to signal day-to-day displacements in determinations of serum calcium. A warning procedure that uses the mean of two control values (Method 2) was compared to a procedure that tested the two control values individually (Method 1). A simulated baseline shift was used to approximate the mechanism of day-to-day displacement. The two methods compared were calibrated to signal a warning with equal frequency in the absence of shift; then the method that signaled with highest frequency under baseline shift was judged most effective. Some statistical models were evolved for the distribution of serum calcium control values. Theoretical comparisons based on these models showed Method 2 to be more effective on the average under a broad range of conditions. However, in an empirical comparison based on 253 pairs of control values, Methods 1 and 2 were about equally effective.


Key Words: statistical treatment of quality-control data

Submitted on November 29, 1973
Accepted on August 2, 1974






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Copyright © 1974 by the American Association for Clinical Chemistry.