How Variable Is the Volar Subcutaneous Tissue of the Digits on B-Mode and Color Doppler Ultrasound in Non-Psoriatic Individuals and Could It Be Included in a Dactylitis Score?

Abstract

Digital subcutaneous tissue (SCT) changes are involved in dactylitis, a hallmark feature of psoriatic arthritis (PsA). There are no studies on the ultrasound (US) characteristics of the digital SCT in the general population. To investigate the variability in US-measured thickness (TH) and color Doppler (CD)-detected blood flow of the SCT of the volar aspects of the fingers in a non-psoriatic population and to investigate the impact of the scanning method and demographics and clinical features on these measurements. SCT TH and semiquantitative (SQD) and quantitative (QD) Doppler signals were measured in the bilateral second finger at the proximal and middle phalangesin81non-psoriatic volunteers [49 female, 32 men; 18-78years]. Two scanning methods with and without (thick gel layer interposition) probe-skin contact were used. Demographics and clinical features were collected. There was high variability of SCT TH and Doppler measurements between individuals. All US measurements obtained without probe-skin contact were significantly greater than their corresponding measurements obtained with the probe contacting the skin (p < 0.001). SCT TH was positively related to dominant hand, age, masculine gender, weight, height, body mass index, and alcohol consumption while Doppler measurements were positively related to age and non-dominant hand. US-measured SCT thickness and Doppler-detected SCT blood flow of the volar aspect of the fingers seem to be highly variable in the non-psoriatic population aswell as highly dependent on the US scanning method. This variability is of utmost importance for assessing dactylitis in PsA.