Rheumatology 2002; 41: 148-152
© 2002 British Society for Rheumatology
Original papers |
Relevant change in radiological progression in patients with hip osteoarthritis. II. Determination using an expert opinion approach
1 René Descartes University, Cochin Hospital, Institut de Rhumatologie, Paris,
2 INSERM U88, St Maurice Hospital, Paris,
3 NEGMA Laboratories, Toussus le Noble,
4 General Hospital, Dijon,
5 Leopold Bellan Hospital, Paris,
6 Rangueil Hospital, Toulouse and
7 Lyon-Sud Hospital, Pierre Bénite, France
Aim. To determine the minimum clinically important difference (MCID) in joint space width (JSW) progression in patients with hip osteoarthritis (OA), based upon evaluation by a panel of clinical experts as a gold standard.
Methods. A sample of 298 patients with hip OA was selected from a multicentre, prospective, longitudinal, 3-yr follow-up study. A pelvic radiograph was obtained at entry and after 3 yr. For each film, the narrowest JSW was measured using a 0.1-mm graduated magnifying glass. The difference between baseline and 3-yr follow-up JSW was calculated. Two senior rheumatologists, who were experts in osteoarthritis, evaluated each pair of films and noted whether a clinically relevant deterioration in osteoarthritis stage occurred at 3 yr compared with baseline. Interobserver reliabilities were evaluated using the 
coefficient and proportions of agreements. Then, for each measured difference in JSW (0.1 mm per 0.1 mm), the sensitivity and specificity for MCID, defined as the assessment of expert 1, expert 2 or a combination of both, were calculated. This allowed us to obtain, from graphic representations of the correct classification probabilities, the best measured JSW threshold, with the maximal true positive and the minimal false positive results.
Results. The mean measured change in JSW was -0.63±0.74 mm. Experts 1 and 2 considered the decrease in JSW to be clinically relevant in 122 (40.9%) and 100 pairs (33.6%) respectively. The proportion of agreements between the experts was 79.9%, with a coefficient of 0.572. The best measured JSW threshold was -0.4 mm for expert 1, expert 2 and the combination of both; sensitivity and specificity were 0.75 and 0.8, 0.71 and 0.72, and 0.75 and 0.7 respectively.
Conclusion. This study suggests that a change of at least 0.4 mm in the radiological JSW could be considered clinically relevant. Other studies using other sets of patients and other methods are needed for validation.
KEY WORDS: Minimum clinically important difference, Hip osteoarthritis, Joint space width, Outcome measure.
Correspondence to: M. Dougados, Institut de Rhumatologie, Cochin Hospital, 27 rue du Faubourg Saint Jacques, 75014 Paris, France.