Background In rheumatoid arthritis (RA), the osteoclast pathway is activated by abnormal immune conditions accompanied by chronic inflammation, ultimately resulting in periarticular and systemic osteoporosis. These conditions expose patients to an increased risk of fracture. It is important to predict the effectiveness of anti-osteoporosis drugs early on in these patients.
Objectives The purpose of this study was to investigate clinical factors associated with spine strength assessed by finite element analysis of clinical computed tomography (CT/FEA) increase to daily teriparatide (TPTD) treatment for 12 months.
Methods A total of 29 RA patients were enrolled in this study. Patients were 68.0±7.9 years old, and the duration of symptoms was 12.2±8.7 years. All patients received TPTD for 12 months and changes in serum procollagen type 1 N-terminal propeptide (P1NP) were evaluated from baseline to 1, 3, 6, and 12 months. Bone mineral density (BMD), assessed by dual X-ray absorptiometry (DXA), and bone strength, assessed by quantitative computed tomography (CT), were determined at baseline and at 12 months. Nonlinear finite element analysis (FEA) was performed on CT to estimate spinal-predicted bone strength (PBS). We used multivariate logistic regression analysis to investigate clinical factors that may help predict changes in PBS.
Results Most subjects showed moderate disease activity (mean baseline Disease Activity Scores assessing with 28 joints with CRP, 2.75±0.79). Patients had significantly greater levels of serum P1NP at all points measured. Mean values at baseline and at 12 months were 0.89 mg/cm2 and 0.94 mg/cm2 (p<0.01) for BMD of the spine (median change, 6.3%), and 3508N and 4070N (P<0.01) for PBS of the spine (mean change, 19.8%). Multivariate logistic regression analysis revealed that a significant indicator of a PBS increase at 12 months was a 1-month absolute change of P1NP. The cutoff value for absolute change was 74.8 mg/dL, and the odds ratio was 29.9 (95% confidence interval, 2.8-939.6) after adjusting for bisphosphonate administration, oral prednisolone dose, and age.
Conclusions Our results showed that an absolute change in P1NP at 1-month was a useful predictor for increases in spine PBS. CT/FEA appears to detect the effects of TPTD more sensitively than DXA.
Disclosure of Interest None declared