Clinical laboratory quality control: a costly process now out of control.

We studied laboratory internal quality control (QC) processes using the College of American Pathologists Q-Probes program. Over 500 institutions participated, providing practices based on approximately 710,000 cholesterol, 880,000 calcium, 400,000 digoxin, and 1,180,000 hemoglobin QC results. The costs of QC included participant median control samples rates comprising 9.1, 9.4, 37.0, and 6.8% for the four analytes respectively, repeat patient test rates of 0.36% for hemoglobin to 0.65% for digoxin, and median delays in reporting results when QC exceptions occurred of 15.8 min for calcium to 24.7 min for hemoglobin. Quality control practices were complex and highly variable among participants and frequently differed from internal laboratory protocols and from long-established quality guidelines. We conclude that QC is costly, and laboratorians frequently do not follow established QC practices, in part because they are complex. To improve compliance, we believe QC practices must be simplified.