USING LINEAR-REGRESSION FOR METHODS COMPARISON

Laboratories use linear. regression as a tool to compare methods, eith er to decide whether to replace one method with another, to compare th e analytical performance of two methods, or to make the results of the two methods equivalent. Linear regression is a requirement in the Nat ional Committee on Clinical Laboratory Standards (NCCLS) document EP9- T, Method Comparison and Bias. Computer software programs can simplify the process. Technologists should be aware of four patterns of bias-c onstant error, proportional bias, random error, and outliers. When det erminingg whether the methods are adequate the technologist evaluates against a predetermined medical decision point, and has predetermined an acceptable range of bias. With these pieces of information, he or s he can calculate the bias and its 95% confidence interval using equati ons in the NCCLS document. This is the second article in a continuing education series on statistics. Other articles in this series focus on the control chart, assessment of linearity and the creation of refere nce ranges.