Additional day-to-day precision estimates based on regional chemistry quality control data.

State-of-the-art precision values are presented for the following serum constituents: aldolase (EC 4.1.2.13), alpha-hydroxybutyrate dehydrogenase (EC 1.1.1.30), cholinesterase (EC 3.1.1.8), cortisol, gamma glutamyl transferase (EC 2.3.2.2), haptoglobin, immunoglobulins, lactic acid, leucine aminopeptidase (EC 3.4.1.1), total lipids, osmolality, protein fractions, T3 uptake, thyroxine and vitamin B12. Precision estimates are based on values reported for four lyophilized serum pools analyzed by participants in the Pennsylvania Association of Clinical Pathologists regional quality control program for clinical chemistry, during 1976, 1977 and 1978. Use of the upper limit of the "most common range" of precision (that range including the 75 percent most precise laboratories) as a warning level for trouble-shooting is advocated.