[Bone mineral density in patients with rheumatoid arthritis]

Patients with rheumatoid arthritis (RA), an immune-mediated inflammatory rheumatic disease with peripheral and systemic involvement, are at increased risk of bone loss and fractures. There are many reasons for the high prevalence of osteoporosis (OP) in RA, including both traditional and specific risk factors such as pain and loss of joint function, medication (corticosteroids, methotrexate), and increased proinflammatory cytokines.

To evaluate bone mineral density status in RA patients, focusing on potential relation with classical risk factors for OP.

One-year prospective observational study on 83 consecutive postmenopausal women, 43 diagnosed with RA (group I), and 40 healthy controls (group II) with no previous condition and medication known to affect bone metabolism and turnover. Bone mineral density (BMD) and T-score evaluated by dual X-ray absorbtiometry (DXA) at three standard skeletal sites (L1-L4 lumbar spine, hip and forearm) (Hologique QDR 100 device), and classical risk factors for osteoporosis were assessed in all patients according to a predefined protocol. Data were analyzed in SPSS-13 using ANOVA, t-Student, chi-square and ROC (Receiver Operator Characteristic).

Decreased BMD was reported in the majority of RA cases, mainly in the spine and femoral neck (86%), but also in total hip (72%); moreover, osteoporosis was commonly demonstrated in lumbar spine and osteopenia at hip level. Statistically significant differences between diagnostic categories (normal, osteopenia, osteoporosis, WHO 1994) (p<0.05), while no significant differences between mean BMD levels in women with and without RA at different skeletal sites were found (t-student, p>0.05). However, considerable BMD variation (51.7% to 102.3%) was suggested in RA as compared to non-RA patients (14.3% to 27%) (ANOVA). Significant differences in mean T-score at total hip and forearm (mainly 33% radius) were noted in patients with and without RA (p<0.05). No relation between osteodensitometric parameters and classical risk factors for OP has been identified in RA, except menopause. Indirect weak statistically significant correlations were found between mean T-score and menopause duration at all skeletal levels (Pearson's rank correlation, p<0.05), except for the femoral neck (r=+0.03, p<0.05).

Decreased BMD is commonly seen in RA patients. Several characteristics based on DXA assessment have been identified, including preference for distinct skeletal sites (spine, hip, distal forearm), and the particular intervention of menopause.