COMPARISON OF THE COMBINED CORTICAL THICKNESS OF THE 2ND METACARPAL WITH SHARPS METHOD FOR SCORING HAND MICRORADIOGRAPHS IN RHEUMATOID-ARTHRITIS

Objective, To compare the correlation and specificity of the combined cortical thickness of the second metacarpal (CCT-MC) with Sharp's meth od (SM) for scoring joint erosions and joint space narrowing in rheuma toid arthritis (RA) and to compare the degree of interobserver agreeme nt between the 2 methods. Methods. Hand microradiographs of 22 women w ith RA, functional classes III and IV, were scored independently by 3 rheumatologists using the CCT-MC and the CCT of the middle phalanx and SM. Results. (1) There was a highly significant correlation between t he total SM score and the CCT-MC for the 3 observers (r = 0.61, p = 0. 0026), but not between the CCT of the middle phalanx and SM (r = 0.15, p = 0.53). There was a lower degree of agreement between the observer s for SM erosion scores compared to the CCT-MC (intraclass correlation 0.88 for the CCT-MC and 0.63 for the SM); (2) Both joint space narrow ing and erosion scores correlated highly with the CCT-MC (r = -0.60, p = 0.004; and r = -0.51, p = 0.014, respectively); (3) CCT-MC measurem ents are more closely related to the inner (d) as opposed to the outer (D) diameter of the 2nd metacarpal; (4) The mean time to obtain the C CT-MC score was 3.43 min (SD = 1.38) versus 9.83 min (SD = 3.20) for S M (p = 0.0001); (5) the derivative, (D-2-d(2))/D-2, was significantly correlated with SM (r = -0.72, p = 0.0002) and its erosion and joint s pace narrowing components (r = -0.63, p = 0.0019; and r = -0.71, p 0.0 002,respectively). Conclusion. The CCT-MC is a rapid, practical method with higher agreement among observers compared to SM and correlates h ighly with SM scores for joint damage in RA. CCT-MC appears to have a higher degree of specificity than other sites for CCT measurement. The CCT-MC is more closely related to the inner diameter than the outer d iameter, which supports the notion that the principal site of accelera ted bone loss due to RA in the hand occurs at the endosteal surface. T he CCT-MC should be further assessed with respect to monitoring radiol ogical progression in RA.