Assessing the prevalence of hand osteoarthritis in epidemiological studies. The reliability of a radiological hand scale

Objective-The hands are often involved in the osteoarthritic disease proces s. A radiological grading scale is presented, derived from a published atla s, to assess the prevalence of hand osteoarthritis (OA) involvement in clin ical and epidemiological studies and its reproducibility is studied. Methods-This hand scale is based on the radiological feature "joint space n arrowing", which represents the macromorphological process of cartilage los s. Osteophytes and sclerosis are less important unless seen in conjuction w ith joint space narrowing. Nine individual joints per hand (four proximal i nterphalangeal joints (PIP), four distal interphalangeal joints (DIP), firs t carpometacarpal joint (CMC-1)) are scored dichotomously for the presence of OA. To save time and to increase reliability a severity grading of radio logical features is not performed. To determine inter-rater and intra-rater reliability of the individual joints and the presence of OA in two separat e joint groups (greater than or equal to 2 PIP or DIP and at least one CMC- 1, used to define "generalised OA" in the ongoing Ulm Osteoarthritis Study) 50 pairs of anteroposterior hand radiographs were read by two investigator s twice within one month. The kappa coefficient was calculated to quantify the strength of associations. Results-On average five minutes were needed to score one hand radiograph. B oth raters were able to reproduce their own readings in all individual join ts and for the presence of OA in two separate joint groups after one month. Reliability was highest for the PIP joints (kappa: 0.56-1.00) it was sligh tly lower for the DIP joints (0.38-0.87), for the CMC-1 joints (0.58-0.69) and for OA in two separate joint groups (0.54). The values for interrater a greement were good as well, kappa coefficients ranged from 0.52 to 0.92. Conclusion-This grading scale was shown to be reliable within and between r eaders for all the individual joints as well as for the presence of OA in t wo separate joint groups. Scoring a limited number of joints dichotomously makes this scale efficient and therefore useful for clinical and epidemiolo gical trials, when dealing with large patient samples.