Digital X-ray: Different Periarticular Hand BMD In PsA and RA After Antirheumatic Treatment

Researchers from St. Vincent’s University Hospital in Dublin have found that in the first year following antirheumatic treatment, those with rheumatoid arthritis (RA) had ongoing bone loss in their hands and those with psoriatic arthritis (PsA) had unchanged periarticular bone density. The research was published in Rheumatology.¹

While previous research has shown that loss of metacarpal bone mineral density (BMD) in the first year after RA diagnosis is predictive of radiologic progression up to 20 years later,² far less is known about periarticular bone changes in early PsA.

To assess changes in hand BMD in patients with early PsA compared with those with RA, Agnes Szentpetery, MD, and colleagues recruited 64 participants (32 with PsA and 32 with RA) ages 18 to 80 years who had recently been diagnosed and were treatment naive.

The researchers performed clinical assessments and radiographic diagnostics, including hand radiographs, and digital x-ray radiogrammetry (DXR) at 0, 3, and 12 months, and compared the mean DXR-BMD for both hands between the two groups, as well as changes in DXR-BMD (mg/cm²/mo).

The researchers found that in RA, mean hand DXR-BMD significantly decreased: it was 578 (66), 574 (71), and 573 (72) mg/cm² at baseline, 3, and 12 months, respectively (0 vs 3 months P = .062; 3 vs 12 months P = .018; 0 vs 12 months P = .043).

In contrast, hand DXR-BMD increased in PsA and was higher throughout the study compared with the RA group, at 584 (55), 585 (54), and 586 (56) mg/cm² at baseline, 3, and 12 months, respectively. Patients on a tumor necrosis factor inhibitor in combination with a synthetic disease-modifying antirheumatic drug (DMARD) had higher hand DXR-BMD at 3 and 12 months compared with those on synthetic DMARD monotherapy (P = .015; P = .021).

“Our observation may indicate that repair mechanisms in periarticular bone are different in early psoriatic arthritis with associated increased cortical bone formation compared with rheumatoid arthritis,” the authors wrote. “This has been suggested previously, but observations were based on patients with established disease.”

Interestingly, increased alcohol intake predicted hand bone loss as early as 3 months after PsA or RA diagnosis. The effect of alcohol on the metacarpal bones has not been previously investigated in the early phase of inflammatory arthritis.

The researchers concluded that their findings support the hypothesis that different mechanisms are involved in hand bone remodeling in PsA, and that further studies are required to assess alcohol’s influence on periarticular bone.

Summary and Clinical Applicability

Researchers have found that following antirheumatic treatment, individuals with RA demonstrated ongoing bone loss in their hands, but those with PsA maintained their periarticular BMD. This suggests that different mechanisms are involved in bone remodeling of the hand in PsA.  This study was limited by the small number of patients analyzed and the nonstandardized treatment regimens used. Future studies employing a standardized treatment protocol may provide further insight into changes in periarticular BMD in the setting of RA and PsA.

Increased alcohol intake and higher swollen joint count were also found to be independent predictors for hand bone loss over 1 year in individuals with RA.  Alcohol intake may be a potentially modifiable risk factor, especially if further studies validate the effects of alcohol on metacarpal periarticular bone in early RA.

References

1.     Szentpetery A, Heffernan E, Haroon M, et al. Striking difference of periarticular bone density change in early psoriatic arthritis and rheumatoid arthritis following anti-rheumatic treatment as measured by digital X-ray radiogrammetry. Rheumatology. 2016; Feb 4. doi:10.1093/rheumatology/kev443. [Epub ahead of print]

1.     Kapetanovic MC, Lindqvist E, Algulin J, et al. Early changes in bone mineral density measured by digital x-ray radiogrammetry predict up to 20 years radiological outcome in rheumatoid arthritis. Arthritis Res Ther. 2011;13(1):R31. doi:  10.1186/ar3259.