Semi-quantitatively scored apical extent of disease predicts change in total lung capacity in patients with systemic sclerosis and early interstitial lung disease

Abstract

Background

Pulmonary function tests (PFTs) and extent of ILD on HRCT predict mortality in systemic sclerosis associated interstitial lung disease (SSc-ILD). It is not known whether location and type in addition to extent of affected lung parenchyma are associated with PFTs changes.

Methods SSc patients from a targeted healthcare program were included when PFTs and visually scored concomitant chest HRCT and PFTs at one year follow-up were available. Lung parenchyma of SSc patients was semi-quantitatively scored by visual assessment (reticulation, ground glass opacities, emphysema and disease extent) at five levels from apex to base. Regression analysis after linearity check and excluding multicollinearity was used to predict changes in PFT parameters (TLC, total lung capacity; FVC, forced vital capacity; DLCO, diffusion capacity for carbon monoxide). Results A total of 185 patients were included (85% female, mean age at first symptoms 40 years). All HRCT variables correlated with PFT parameters cross-sectionally. Disease extent and reticulation at the apices (level 1), reticulation at level 2, disease extent and reticulation at level 3 all correlated significantly with TLC (r 0.151–0.17, p < 0.05). Of these HRCT variables disease extent at level 1 predicted change in TLC (adjusted R2 0.024, p 0.021) and when excluding patients with emphysema or pulmonary hypertension, reticulation at level 3 predicted change in TLC (adjusted R2 0.026, p 0.020). Conclusions In patients with systemic sclerosis and lung involvement, disease extent and reticulation at the mid-upper zones predicted change in TLC which may be of clinical importance.