Ultrasound and elastography in the assessment of skin involvement in systemic sclerosis: A systematic literature review focusing on validation and standardization - WSF Skin Ultrasound Group.

OBJECTIVE: To summarize the published evidence in the literature on the role of ultrasound and elastography to assess skin involvement in systemic sclerosis (SSc). METHODS: A systematic literature review (SLR) was performed within the "Skin Ultrasound Working Group" of the World Scleroderma Foundation, according to the Cochrane Handbook. A search was conducted in Pubmed, Cochrane Library and Embase databases from 1/1/1979 to 31/5/2021, using the participants, intervention, comparator and outcomes (PICO) framework. Only full-text articles involving adults, reported in any language, assessing ultrasound to quantify skin pathology in SSc patients. Two reviewers performed the assessment of risk of bias, data extraction and synthesis, independently. RESULTS: Forty-six studies out of 3248 references evaluating skin ultrasound and elastography domains were included. B-mode ultrasound was used in 30 studies (65.2%), elastography in nine (19.6%), and both methods in seven (15.2%). The ultrasound outcome measure domains reported were thickness (57.8%) and echogenicity (17.2%); the elastography domain was stiffness (25%). Methods used for image acquisition and analysis were remarkably heterogeneous and frequently under-reported, precluding data synthesis across studies. The same applies to contextual factors and feasibility. Our data syntheses indicated evidence of good reliability and convergent validity for ultrasound thickness evaluation against mRSS and skin histological findings. Stiffness and echogenicity have limited evidence for validity against histological findings. Evidence for sensitivity to change, test-retest reliability, clinical trial discrimination or thresholds of meaning is limited or absent for reported ultrasound domains. CONCLUSION: Ultrasound is a valid and reliable tool for skin thickness measurement in SSc but there are significant knowledge gaps regarding skin echogenicity assessment by ultrasound and skin stiffness evaluation by elastography in terms of feasibility, validity and discrimination. Standardization of image acquisition and analysis is needed to foster progress.

Assessment of capillary density in systemic sclerosis with three different capillaroscopic methods.

OBJECTIVES: Capillary abnormalities, such as the enlargement and/or disappearance of capillary loops, occur early in the majority of patients with systemic sclerosis (SSc). The aim of this study was to compare three capillaroscopic methods of determining the capillary density in patients with SSc. METHODS: Two of the three methods involved stereo-zoom microscopy at a magnification of 20 times, used either for direct counting, or with a camera and imaging software for determination of the capillary density on coded images. The third method was computerised nailfold video capillaroscopy with 300 x magnification using coded images. The capillary density (loops/mm) was determined on the fourth finger of the non-dominant hand with all three methods in 40 patients, 32 with limited cutaneous SSc (lcSSc) and 8 with diffuse cutaneous SSc (dcSSc), and in 21 healthy control subjects. RESULTS: The median values of capillary density assessed with the three methods were: 4.3, 5.4 and 6.1 loops/mm in lc-SSc patients, 4.5, 5.0 and 6.3 loops/mm in dcSSc patients, and 7.0, 7.0 and 6.9 loops/mm in the controls. Capillary density was thus lower in lcSSc and dcSSc patients than in the controls according to all three methods. Agreement between the three methods was good in the controls. In patients, direct counting resulted in lower values than in the two computer-based methods. CONCLUSIONS: Assessment of capillary density with three different methods showed good agreement between methods. All methods could differentiate between SSc patients and controls.

A multicentre study on the reliability of qualitative and quantitative nail-fold videocapillaroscopy assessment.

OBJECTIVE: To investigate the inter- and intra-observer reliability of both qualitative and quantitative parameters used in the assessment of nail-fold capillaroscopy images. METHODS: Fifty mosaic nail-fold images of healthy controls (n = 10), patients with primary RP (n = 10) and SSc (n = 30) were assessed in random order by two blinded observers on two occasions at centres in Sweden, UK and The Netherlands. Each image was therefore scored by six observers twice. RESULTS: Inter- and intra-observer reliability of quantitative parameters showed substantial to almost perfect agreement [inter- and intra-observer weighted κ's for the number of widened capillaries was 0.75 and 0.87 and giant capillaries was 0.84 and 0.92, intra-class correlation coefficients (ICCs) for capillary density was 0.87 and 0.92 and total loop width was 0.94 and 0.98, respectively]. Qualitative parameters including architecture, avascularity, haemorrhage, crossed, ramified and bushy capillaries showed moderate to substantial inter-observer reproducibility (weighted κ ranging from 0.47 to 0.73), and substantial intra-observer repeatability (weighted κ ranging from 0.71 to 0.80), whereas the scoring of tortuous and bizarre capillaries showed poor inter-observer and substantial intra-observer agreement (inter-observer weighted κ's was 0.39 and 0.21 and intra-observer weighted κ's was 0.68 and 0.76, respectively). CONCLUSION: All quantitative and certain qualitative parameters are highly reliable in terms of inter- and intra-observer agreement. A combination of parameters with the highest reliability should be incorporated into future capillaroscopic scoring systems in studies of prediction and monitoring of SSc spectrum disorders.