BMD Loss Predicts Joint Damage in Rheumatoid Arthritis

A decrease in bone mineral density (BMD) has been shown to predict radiographic joint progression in early rheumatoid arthritis, but a new study suggests BMD loss just 3 months after diagnosis can independently predict radiologic damage at 1 year.

For patients with a diagnosis of rheumatoid arthritis, early treatment with disease-modifying antirheumatic drugs (DMARDs) is known to improve disease outcomes. However, improved prediction of the individual disease course could help doctors optimize antirheumatic therapy.

Digital X-ray radiogrammetry (DXR) uses computerized analyses of standard hand radiographs to estimate peripheral BMD of the 3 middle metacarpal bones (DXR-BMD). Although DXR-BMD loss has repeatedly been shown to predict radiographic joint progression in early rheumatoid arthritis, the majority of previous studies have been based on a 12-month change.

Led by Michael Ziegelasch of Linköping University in Sweden, researchers writing in Arthritis Research & Therapy found that DXR-BMD loss during the initial 3 months after rheumatoid arthritis diagnosis independently predicted radiologic damage at 1 year. Because evaluation of prescribed DMARDs often is performed 3 months after initiation in clinical practice, additional information on the patient’s radiographic prognosis at this time would be highly valuable to optimize future therapy decisions.

The study

This study consisted of 176 patients with early rheumatoid arthritis from 3 Swedish rheumatology centers. All patients fulfilled the 2010 American College of Rheumatology (ACR)/European League Against Rheumatism (EULAR) or the 1987 ACR classification criteria for rheumatoid arthritis.

Pharmacotherapy was prescribed as found appropriate by the treating rheumatologist, according to Swedish guidelines, wherein 91% received conventional synthetic DMARDs (1 patient started on a tumor necrosis factor inhibitor at baseline). Patients were monitored for 2 years, and 14.4% received biologic therapy in the follow-up period.

Radiographs (posterior-anterior projection) of the hands, wrists, and forefeet were performed at baseline, 3 months (hands only), and 1 and 2 years. The radiographs were evaluated according to the Larsen score. Radiographic progression was defined as a difference in Larsen score above the smallest detectable change of the corresponding reader.

DXR-BMD was assessed at inclusion and after 3 months and was categorized as a moderate decrease in DXR-BMD (≥ 0.25 but < 2.5 mg/cm² per month) or a severe decrease (≥ 2.5 mg/cm² per month).

The findings

The analysis included 167 patients, of whom 32 (19%) had radiographic progression at 1 year. The change in DXR-BMD over 3 months showed loss in 98 patients (59%). The DRX-BMD loss was moderate in 73 (44%) of these patients and severe in 25 (15%) patients. “We found that DXR-BMD loss during the initial 3 months independently predicted radiologic damage at 1 year,” the researchers concluded.

Of the 167 patients analyzed, 129 also underwent radiography at 2 years, at which time 45 (35%) showed radiographic progression. However, researchers found no predictive value of DXR-BMD loss in relation to the 2-year radiographic outcome.

Implications for physicians

Based on these results, early DXR-BMD assessments seem to be of clinical value. “Particularly in early disease, additional information on the patient’s radiographic prognosis would be highly valuable in order to optimize therapy decisions,” the researchers concluded.

Although DXR-BMD appeared to have predictive value in relation to 1-year radiographic outcomes, no such relation was found in relation to the 2-year radiographic outcomes. One possible explanation for these disparate findings could be that potent instituted pharmacotherapy attenuated radiographic differences over time.

In addition, the association between DXR-BMD loss and radiographic damage at 1 year remained statistically significant even after excluding the 38 patients without 2-year radiographs.

Still, future studies should compare the value of DXR-BMD with other imaging modalities, the researchers suggested.

References:

Ziegelasch M, Forslind K, Skogh T, et al. “Decrease in bone mineral density during three months after diagnosis of early rheumatoid arthritis measured by digital X-ray radiogrammetry predicts radiographic joint damage after one year.” Arthritis Res Ther. 2017 Sep 2;19(1):195. doi: 10.1186/s13075-017-1403-0.