Background Peripheral bone mineral density (BMD) can be decreased in early rheumatoid arthritis but it is unknown if BMD loss emerges already before arthritis is clinically apparent.

Objectives We aimed to study if BMD loss occurs in patients with clinically suspect arthralgia (CSA), if it is associated with progression to clinical arthritis and if it is associated with MRI-detected subclinical inflammation.

Methods Patients with CSA had arthralgia for <1 year and were suspect to progress to RA according to their rheumatologists. At baseline a 1.5T MRI was performed of unilateral MCP, wrist and MTP-joints and scored on synovitis, bone marrow edema and tenosynovitis;. summing these features yielded the MRI-inflammation score. Digital X-ray radiogrammetry (DXR) was used to measure BMD on two sequential conventional hand radiographs (mean interval between radiographs 4.4 months). The change in BMD was studied; BMD loss was defined as decrease of ≥2.5 mg/cm²/month. Patients were followed on arthritis development for median 18.4 months.

Results In CSA-patients (n=108) change in BMD was negatively associated with age (β=-0.03, p=0.007). Within CSA-patients BMD loss was associated with arthritis development (adjusted for age HR=6.1, 95%CI=1.7;21.4) and was most frequently measured in the months before clinical arthritis development. The MRI-inflammation scores were associated with the change in BMD (adjusted for age β=-0.05, p=0.047). The MRI-inflammation score and BMD loss were both independently associated with arthritis development (HR=1.1 95%CI=1.1;1.2 and HR=4.6 95%CI=1.2;17.2 respectively).

Conclusions In CSA-patients BMD loss is associated with MRI-detectable subclinical inflammation and with progression to clinical arthritis.

Disclosure of Interest L. Mangnus: None declared, H. van Steenbergen: None declared, M. Reijnierse: None declared, J. Kälvesten Employee of: Sectra AB, A. van der Helm-van Mil: None declared