The clinical value of the delta finger to palm distance in systemic sclerosis

Systemic sclerosis (SSc) is a collagen-vascular disorder characterized by fibrosis and vasculopathy. Delta finger to palm distance (delta FTP) is an index measuring the distance between the tip of the third finger to the distal palmar crease in the flexed and extended position. The present study aimed to evaluate the clinical value of delta FTP and to assess the correlation of delta FTP with modified Rodnan skin score (mRSS) and forced vital capacity (FVC) over the 12-month follow-up. This prospective longitudinal study began with 50 participants who were followed for twelve months. Lowess smoothing and linear regression were applied to detect and assess the relationship between delta FTP and mRSS. p-values were adjusted by the Benjamini-Hochberg method (BHM) as a control for false discovery rate. Delta FTP was lower among patients with higher disease duration (p-value^adj: 0.008), diffuse cutaneous SSc (p-value^adj: 0.006), digital ulcers (p-value^adj: 0.003), telangiectasia (p-value^adj: 0.006) and dysphagia (p-value^adj: 0.036). The mRSS has a significant negative linear effect on the delta FTP at the baseline and the end of the follow-up (r: -0.31 and -0.40, respectively). Moreover, changes of mRSS and delta FTP showed a negative linear association over time (r: -0.22). These linear effects remained significant after regrouping the patients based on their SSc subtype. Delta FTP and FVC were not correlated either at the baseline or at the end. It seems that the delta FTP can be a valuable clinical index, supported by its correlated changes with mRSS and other SSc clinical manifestations over the one-year follow-up.