Background In patients with established RA, radiological progression is preceded by metacarpal bone mineral density (mBMD) loss.

Objectives To assess whether in early (rheumatoid) arthritis patients, mBMD loss after 4 months is an independent predictor for radiological progression after 1 year of antirheumatic treatment.

Methods mBMD was measured in metacarpals 2-4 by digital X-ray radiogrammetry (DXR) in patients participating in the IMPROVED study, a single blind multicenter study in 479(79%) RA (2010 ACR/EULAR criteria, symptom duration < 2 years) and 122(20%) UA (arthritis >1 joint, at risk for developing RA by rheumatologists estimation but not fulfilling the 2010 criteria) patients. All patients started treatment with 4 months of methotrexate (MTX) and a tapered high dose of prednisone, followed by tapering or adjusting treatment aiming at DAS <1.6. We performed univariable logistic regression with radiologic progression (increase in total Sharp-van der Heijde Score (tSHS) ≥0.5 after 1 year) as dependent variable and mBMD loss after 4 months and other known predictors as covariates. For power reasons, we selected those two univariable predictive variables (p-value ≤0.10) with the lowest p-value for multivariate regression.

Results Of 237 patients (43(18%) UA, 192(81%) RA, 2 missing classification) mBMD measurements at baseline and 4 months and radiological progression data after 1 year were available. Median mBMD loss after 4 months (4mo-mBMD loss, mg/cm² unless indicated otherwise) was 2.3(-1.7 to 6.8) (corresponding to 0.6(-0.4 to 1.7) mg/cm²/month). Seventeen (7%) patients had radiological progression after 1 year and 220(93%) had not. Patients with radiological progression had a median (IQR) 4mo-mBMD loss of 5.5(2.7 to 13.6) compared to 2.0(-2.0 to 6.6) in patients without progression (corresponding to 1.4(0.7 to 3.4) and 0.5(-0.5 to 1.6) mg/cm²/month), (p=0.002). Univariable predictors for progression (OR (95%CI) were age (1.0(1.0-1.1)), fulfilling the 2010 criteria for RA (6.4(0.9-48)), postmenopausal status (6.2(1.4-27)), ESR (1.0(0.999-1.0)), tSHS (1.1(0.996-1.1)), presence of erosions (4.4(2.0-10.0)) and presence of ACPA (3.5(1.3-9.4)), all at baseline, and 4mo-mBMD loss (mg/cm²/months) (1.5(1.2-1.9)). Female gender, RF positivity, symptom duration, baseline swollen and tender joint counts were not predictive. Independent predictors for progression after 1 year were presence of baseline erosions (5.2(1.7-16)) and 4mo-mBMD loss (mg/cm²/month) (1.5(1.1-2.0)). In 203(86%) patients who had no erosions at baseline, 4mo-mBMD loss (mg/cm²/month) was the only independent predictor for progression after 1 year (1.8(1.3-2.7), adjusted for age).

Conclusions In early (rheumatoid) arthritis patients, mBMD loss after 4 months of MTX and prednisone is an independent predictor for radiological joint damage progression, despite the fact that radiological progression was only present in 7% of patients after 1 year of a remission steered treatment strategy. In particular in patients who are non-erosive at baseline, mBMD loss after 4 months may help to steer treatment decisions as predictor of damage progression.

Disclosure of Interest None Declared