Background/Purpose:   Digital X-ray radiogrammetry (DXR) is a method to calculate peripheral bone mineral density (BMD) which calculates BMD of the hands (DXR-BMD). The aim of this study was to evaluate whether hand bone loss (HBL) during the initial three months after diagnosis predicts radiographic joint damage after 12 and 24 months in patients with rheumatoid arthritis (RA).

Methods:   Patients with early RA (<12 months since symptom onset) were consecutively included from three Swedish rheumatology departments (and treated according to the Swedish guidelines). Radiographs of hands and feet were taken at baseline, 3 months (hands only), 12 and 24 months. The baseline, 12 and 24 months radiographs were evaluated according to the Larsen score by one reader at each centre. The smallest detectable change (SDC) was established for each reader individually. DXR-BMD was performed on radiographs of the hands taken at baseline and after 3 months. Changes in BMD were evaluated in metacarpals 2, 3 and 4. HBL was defined either as a moderate change in DXR-BMD (≥0,25 but <2,5 mg/cm² per month) or a severe change (≥2,5 mg/cm² per month), as defined by the device manufacturer Sectra AB, Sweden. Radiographic progression was defined as a difference in Larsen score above the SDC [of the corresponding reader]. Statistical calculations were performed using SPSS 23 software. After testing different variables in a simple regression with change in Larsen score as dependent variable, all variables with the lowest p-value (p<0.2) were extracted to perform univariate analysis of variance. ESR and anti-CCP were measured at baseline and DAS28 was evaluated at each visit.

Results:   One hundred and sixty seven patients (64% women) with a mean disease duration of 6 months (SD 3.7) and mean age 58 years (SD 14.5) were included. 63% tested positive regarding serum anti-CCP antibodies. HBL occurred in 58.7% of the patients (44.3% moderate and 14.4% severe HBL). Thirty two patients (19.2%) had radiographic progression at 12 months and 45 (34.9%) at 24 months. Greater HBL within 3 months associated significantly (p= 0.033) with greater increase in Larsen score between baseline and 12 months, adjusted for sex and baseline values of ESR, DAS28, Larsen score and anti-CCP status. No significant association was observed between early bone loss and radiological damage at 24 months (p=0.626).  

Conclusion:   HBL during the initial three months is an independent predictor of radiologic joint damage at 12 months in patients with early RA, but does not predict the 24 months outcome. Thus, DXR-BMD examinations after three months may be useful to detect ongoing joint damage, but the long-term predictive ability seems to be limited.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/decrease-in-bone-mineral-density-during-three-months-of-early-ra-measured-by-dxr-predicts-radiographic-joint-damage-after-one-year/