The effect of analyte and analyte concentration upon precision estimates in clinical chemistry.

A significant statistical relationship between concentration and precision is shown for 11 of 14 clinical chemistry analytes, and quantitative expressions of these relationships are given. The relationships are not necessarily the same for automated and manual methods for a given analyte. Automated precision is not significantly better than manual precision for triglyceride, cholesterol and sodium. For 11 other analytes, automated precision is superior at some or all concentrations. State of the art precision is compared with criteria of medical significance. Only calcium shows significantly poorer precision than that required by medical goals.