The smallest detectable difference and sensitivity to change of magnetic resonance imaging and radiographic scoring of structural joint damage in rheumatoid arthritis finger, wrist, and toe joints: a comparison of the OMERACT rheumatoid arthritis magnetic resonance imaging score applied to different joint combinations and the Sharp/van der Heijde radiographic score.

OBJECTIVE: To compare 2 magnetic resonance imaging (MRI) approaches and radiographic evaluation according to the Sharp/van der Heijde method with respect to sensitivity to change in joint destruction in patients with rheumatoid arthritis (RA).
METHODS: Thirty-five RA patients and 9 healthy controls underwent MRI and radiography on 2 occasions 1 year apart. Conventional radiographs of the hands, wrists, and forefeet were evaluated according to the Sharp/van der Heijde method. MRIs of unilateral wrist and second through fifth metacarpophalangeal (MCP) joints ("few-joints approach") and of bilateral wrist and MCP joints plus unilateral metatarsophalangeal (MTP) joints ("many-joints approach") were assessed for bone erosions according to the scoring system recommended by the OMERACT (Outcome Measures in Rheumatology Clinical Trials) group. The smallest detectable differences (SDDs) of the radiography and MRI scores were computed based on reevaluation of one-third of the study population.
RESULTS: Progressive joint destruction, i.e., an increase in score after the followup period, was observed more frequently with the MRI "many-joints approach" (30 subjects) and "few-joints approach" (25 subjects) than with the Sharp/van der Heijde radiographic method (9 subjects) (P < 0.001 by chi-square analysis). No significant difference between the MRI approaches was observed. When only subjects with a change greater than the SDD were considered, progression was revealed with the MRI "many-joints approach," the MRI "few-joints approach," and radiography in 15, 13, and 5 RA subjects, respectively. With both MRI approaches, significantly more subjects with progression were detected than were detected by radiography (P < 0.05).
CONCLUSION: MRI, regardless of whether it covers unilateral wrist and MCP joints or bilateral wrist and MCP joints plus unilateral MTP joints, is significantly superior to radiography of the hands, wrists, and forefeet with respect to detection of progressive joint destruction in RA.