Background/Purpose: Rheumatoid arthritis (RA) and ankylosing spondylitis (AS) have both been associated with generalized and localized bone loss. Inflammatory cytokines like tumor necrosis factor (TNF) have been implicated in bone resorption and, therefore, anti-TNF biologics may improve bone status. There have been very few observational or longitudinal data on the use of peripheral quantitative computed tomography (QCT) for determining changes in bone status in anti-TNF-treated RA and AS patients. Therefore, we assessed volumetric bone mineral density (BMD) by forearm QCT in conjunction with disease activity, dual-energy X-ray absorptiometry (DXA) and bone biomarker parameters in a mixed cohort of RA and AS patients.

Methods: Fifty-three consecutive patients including 36 RA patients treated with etanercept (ETN) or certolizumab pegol (CZP) and 17 AS patients treated with ETN were included in a 12-month follow-up study. Volumetric (3-dimensional) and areal (2-dimensional) BMD were determined by peripheral QCT and DXA, respectively. Bone biomarkers, such as calcium, phosphate, PTH, osteocalcin, soluble RANKL, vitamin D3, P1NP, CTX, sclerostin, DKK-1 and cathepsin K (CATHK) were assessed by ELISA. DAS28 and BASDAI served as markers of disease activity in RA and AS, respectively. Determinants of volumetric BMD were investigated by uni- and multivariable regression analyses, as well as RM-ANOVA.

Results: One-year ETN or CZP therapy arrested further progression of bone loss in the radius in RA and AS as determined by peripheral QCT. Volumetric (QCT) and areal (DXA) BMD showed significant, variable correlations with each other (p< 0.05). The univariable analysis showed that total QCT BMD after 12 months was inversely determined by disease activity at baseline (p=0.030). Cortical BMD was negatively determined by baseline disease activity (p=0.005), as well as baseline (p=0.025) and 12-month CATHK levels (p=0.033). The negative associations of 12-month total (p=0.030) and cortical BMD (p=0.012) with baseline disease activity was also confirmed by multivariable analysis. The change in QCT trabecular BMD between baseline and 12 months was related to the anti-TNF treatment together with higher baseline vitamin D3 levels (VITD3-0) (p=0.031). In addition, TNF inhibition and lower cathepsin K determined cortical BMD changes over the one-year period (p=0.006).

Conclusion: QCT may be a suitable methodology to measure volumetric BMD in various compartments (trabecular and cortical) of the radius. QCT confirmed that biologics may arrest generalized bone loss. Moreover, we identified baseline parameters, such as disease activity, CATHK and possibly VITD3 that may predict the effects of one-year anti-TNF treatment on volumetric BMD changes over time.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/use-of-peripheral-quantitative-computed-tomography-in-the-assessment-of-bone-mineral-density-in-anti-tnf-treated-rheumatoid-arthritis-and-ankylosing-spondylitis-patients/