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Abstract: Objectives. – To quantify asymmetry of radiological joint damage in rheumatoid arthritis (RA), to determine whether asymmetrical damage to joints in RA becomes symmetrical over time, and to identify factors predictive of symmetrization. Patients and methods. – In phase 1, initial, mid-term (mean follow-up: three years) and late (mean follow-up: eight years) radiographs of 48 patients with definite RA (English population) were graded by the Modified Larsen (ML) system. In phase 2, 27 subjects (Canadian population) with at least one asymmetrical pair of joints in the hands or feet were identified. Two successive radiographs of 77 asymmetrical joints, separated by at least two years, were compared. Clinical and biological factors were assessed for their ability to predict symmetrization, defined as a reduction in side-to-side difference over time of two or more ML grades. Results. – In phase 1, the overall rate of asymmetry was 12.9% (95% C.I.: 11.2%–14.5%), increasing from 9.7% (first visit) to 13.8% (mid-term) and 14.4% (last visit). Metacarpophalangeal (MCP) joints were more frequently asymmetrical than thumb (MCP and interphalangeal) joints (p=0.0064) and proximal interphalangeal (PIP) joints (p<0.0001); wrist quadrants were more frequently asymmetrical than PIP joints (p<0.0001). In phase 2, two groups were identified and compared: symmetrizers (22 joints) and non-symmetrizers (55 joints). The overall probability of small joints in the hand and foot symmetrizing was 28.5%. Rheumatoid factor (RF) was predictive of symmetrization. The risk of symmetrization was significantly increased in RF-positive patients with asymmetric joints (p=0.01). The prevalence of asymmetry did not decrease with disease duration, despite symmetrization. Conclusions. – Prevalence of asymmetry in joint damage in RA was 13 to 16%. Symmetry was more evident in PIP joints than in MCP and wrist joints. Seropositive patients are more than twice as likely to symmetrize than seronegative patients. Data regarding the tendency for symmetrization may have value in the clinical management of RA patients with asymmetrical joint damage. [Copyright &y& Elsevier]

Objectives. – To evaluate observer agreement using the Larsen system (LS) and a modified Larsen system (ML) when assessing individual joints of the hands and wrists in rheumatoid arthritis, and to compare the two systems. To determine the minimally important difference (MID) for the ML.Methods. – Thirty radiographs of hands and wrists from 10 patients who presented with RA were graded by two blinded observers, using the LS and then the ML. Patients were followed for a mean of 7.2 years (range: 4–10 years). Inter- and intra-observer agreement were calculated using the kappa statistic with linear incremental weights. Inter-observer agreement was also computed for the summed score, using an intra-class correlation coefficient. Inter-observer error was estimated by calculating the mean and standard deviation of the grading differences between the two observers. Prevalence of damage was calculated as a ratio of damage:no damage and expressed as a percentage. Pairs of radiographs were comparatively graded using a 7-point Likert scale.Results. – The kappa statistic for inter-observer agreement was 0.38 (marginal reproducibility) for the LS and 0.52 (good reproducibility) for the ML (P = 0.004). Using a difference of one grade as perfect agreement, it was 0.56 (good reproducibility) for the LS and 0.87 (excellent reproducibility) for the ML (P = 0.001). Intra-observer agreement was high in both systems. The distribution of ML-grade differences varied according to the level of the Likert scale: for “a little bit worse”, representing the smallest amount of detectable damage progression, the distribution differences peaked around two grades. This value represented a MID 87% of the time.Conclusions. – The LS lacks precision for individual joints. The ML, it is proposed, has more detailed definitions of grades, and is more reliable. When pairs of radiographs were compared, a two-grade difference on the ML was the MID. [Copyright &y& Elsevier]