Statistical evaluation of agreement between two methods for measuring a quantitative variable

Abstract

Herein we suggest that two methods for measuring a quantitative variable can be judged interchangeable provided all of the following conditions are met: first, the methods must not exhibit marked additive or nonadditive systematic bias; second, the difference between the two mean readings is not 'statistically significant'; third, the lower limit of the 95% confidence interval of the intraclass correlation is at least 0.75. Statistical procedures to evaluate these conditions of interchangeability are described in detail. A computer program coded in SAS to carry out the procedures is listed in the Appendix. A similar program coded in DBASE III PLUS for the microcomputer is available upon request.