Nailfold Capillaroscopy Patterns Are Associated with Impairment of DLCO in Very Early Diagnosis of Systemic Sclerosis: Insights of a Pulmonary-Vascular Interplay.

Background/Objectives: Data regarding the association between diffusing lung capacity for carbon monoxide (DLCO) and nail-fold Videocapillaroscopy (NVC) patterns are sparse in Very Early Diagnosis of Systemic Sclerosis (SSc; VEDOSS). The aim of this study was to detect differences in VEDOSS patients exhibiting reduced versus normal values of DLCO/single-breath (SB)% predicted (with a cut-off of 80%). Methods: A cross-sectional study was conducted in 65 VEDOSS patients, enrolled due to their fulfillment of the 2021 criteria, while not meeting the 2013 ACR/EULAR Criteria. Pulmonary function tests and NVC evaluations were conducted from January to March 2026. Univariate tests were used for intergroup analysis. Logistic and linear regression models were employed to identify predictors of DLCO/SB < 80% and DLCO/SB% values, respectively. p-values < 0.05 were considered statistically significant. Results: Forty-two (64.6%) patients reported preserved DLCO/SB% and twenty-three (35.4%) exhibited reduced DLCO/SB%. Patients with only ANA positivity were more prevalent in the DLCO-preserved group (p = 0.026), while SSc-specific autoantibodies were more frequently present in the DLCO < 80% group (p = 0.028), as well as gastrointestinal symptoms (p = 0.039). The late pattern was identified exclusively in the DLCO < 80% group (p = 0.013), while patients with advanced NVC abnormalities (namely, the active/late pattern) reported lower values of DLCO/SB%. A logistic regression model confirmed a trend toward significance in predicting reduced DLCO for the active/late pattern, while the latter was negatively associated with the unitary increase in DLCO/SB% values (standardized β= -0.38, p = 0.008) in linear regression analysis. Conclusions: Reduced DLCO/SB (<80%) is associated with an active/late pattern on NVC in VEDOSS.