Variability of precision in scoring radiographic abnormalities in rheumatoid arthritis by experienced readers.

Abstract

The variability in scoring radiographic abnormalities is considerable among this group of 11 expert readers. This has important implications for power calculations in comparison studies such as therapeutic trials and for cross-trial comparisons. The correlation between the difference in repeated scores and their means indicates systematic error (bias), which, if corrected, may improve the detection of treatment effects when using a responder-type analysis. These and other design and analysis issues are discussed.