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We read with interest the report of the WOSERACT trial1 that compared the addition of 7 mg daily prednisolone or placebo to sulfasalazine in early rheumatoid arthritis (RA). A number of important aspects of the trial have been dealt with well: the sample size is adequate; appropriate attention has been paid to confounders; two separate and independent readers scored the radiographs; the 2 year trial was of adequate length; and the completeness of the data is satisfactory. Given these strengths, it is all the more disappointing that the results of the main outcome, radiographic damage, cannot be adequately interpreted as they are reported. Indeed, the validity of these results is open to serious doubt. We feel there is a real possibility of a type II statistical error (missing a true difference between treatment arms). There are two (possibly three) reasons for this.
Firstly, there is an absolute difference between the x ray scores of the two readers of about 40 Sharp points. This raises strong doubts over the proficiency of either or both readers. In early RA Sharp scores are typically very low, with most patients scoring 0 and only a few with higher scores. Scores of 80, let alone 159, after one year of RA are without precedent in the literature, and even the baseline medians of 6 and 8 recorded for the conservative reader are quite high. In contrast with the authors, we cannot be “reassured” by their assertion that “the change in x ray score was consistent between the two readers”: these data are simply not provided in the report. All we have is an unsatisfactory correlation of absolute scores between readers of 0.8 (whereas in most trials the intraclass correlation coefficient (the recommended and more severe test of reliability between readers) exceeds 0.9), and the …
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