To compare the sensitivity and efficiency of 3 different radiologic scoring systems in measuring radiologic progression of rheumatoid arthritis (RA) over a 12-year period.
Radiographs of the hands and feet of 112 RA patients were assessed at 0, 3, 6, and 12 years of disease duration using the Sharp score as modified by van der Heijde (SHS), the Sharp score with increased maximum scores (Sharp Max), and the Kellgren score. The sensitivity to change was tested using the standardized response mean (SRM); the efficiency was determined by calculating the number of patients needed to detect 50% difference in progression between 2 patient groups.
Radiologic abnormalities were steadily progressive irrespective of the scoring method used. In early disease, the SRM was significantly larger for the SHS and Kellgren scores compared with the Sharp Max score. In late disease, the Kellgren score was slightly more sensitive to change compared with the SHS and Sharp Max scores; the difference, however, did not reach significance. In erosive disease, the SRM was significantly larger for the Kellgren compared with the SHS and Sharp Max scores. The numbers of patients needed to detect a 50% difference during the 0-3-year followup period were 129, 138, and 124 for the SHS, the Sharp Max, and the Kellgren, respectively. The numbers of patients needed to detect a 50% difference during the 6-12-year followup period were 117, 121, and 104, respectively. The numbers of patients needed to detect a 50% difference during the 6-12-year followup in patients with erosive disease were 74, 78, and 68, respectively, for the 3 scores. The Kellgren required 33 minutes to score 10 sets of radiographs of the hands and feet; the SHS score took 55 minutes.
The Kellgren scoring system is the most efficient method for monitoring the radiologic progression of RA. The Kellgren and the SHS are equally sensitive to change early in the disease, whereas the Kellgren score becomes more sensitive to change late in the disease in patients with erosions.