An evaluation of the efficacy of the toe brachial index measuring vascular involvement in systemic sclerosis and other connective tissue diseases

Objective. The ankle and toe brachial indices (ABI and TBI) are calculated as the ankle and toe systolic blood pressures divided by the highest brachial systolic pressure, respectively. We sought to evaluate the efficacy of ABI and TBI as an objective, non-invasive assessment of vascular involvement in patients with systemic sclerosis (SSc) and to investigate the clinical significance of TBI in SSc. Methods. ABI and TBI were measured using an oscillometric method in 136 outpatients, including 77 with SSc, 29 with systemic lupus erythematosus (SLE), 16 with primary Sjögren's syndrome (SjS), and 14 with dermatomyositis (DM). We also analyzed 21 healthy controls. Results. The mean ABI and frequency of reduced ABI values (<1.0) did not differ significantly between disease groups. TBI values in patients with SSc and lSSc were significantly lower than in those with SjS and DM, respectively (p<0.01). Patients with SSc and lSSc had significantly lower TBI values than healthy controls (p<0.05). Reduced TBI values (<0.6) were significantly more common in patients with SSc, including both dSSc and lSSc, than in those with SLE (p<0.05). Similarly, the frequency of decreased TBI was higher in patients with SSc and dSSc than in those with SjS or healthy controls (p<0.05). Skin ulcers (p=0.041) or overlap with rheumatoid arthritis (p=0.018) were associated with reduced TBI values by logistic regression analysis. Conclusion. The TBI value is a useful, non-invasive tool to evaluate vascular involvement in SSc.