Induced Sputum Analysis in Subjects With Systemic Sclerosis

Induced sputum is a noninvasive tool, aimed at collecting cellular and soluble materials from lung airways. Induced sputum sampling analysis has been validated in chronic obstructive lung diseases as well as in various diffuse interstitial lung disorders. Our objective was to evaluate the utility of induced sputum speciments of cellular and soluble materials noninvasively sampled from the lung airways of subjects with systemic sclerosis compared with healthy controls and determine possible correlation with disease manifestations.

The study population included 20 consecutive subjects with systemic sclerosis and 16 healthy volunteers (controls). All of the participants underwent pulmonary function testing (PFT), single-breath diffusion capacity of carbon monoxide, and induced sputum cytology analysis.

The systemic sclerosis subjects' induced sputum samples contained a higher neutrophil count (P = .09) and lower lymphocyte count (P = .045) compared with the controls. Within the systemic sclerosis population, several clinical, PFT, and induced sputum findings were positively correlated: the modified Rodnan skin score score and CD3 (P = .044), modified Rodnan skin score and CD4 (P = .04), modified Rodnan skin score and percentage neutrophils (P = .059), and total lung capacity (TLC) and percentage lymphocytes (P = .02). Induced sputum neutrophil counts were inversely associated with TLC (P = .02) and FVC (P = .02). Induced sputum samples from the subgroup of systemic sclerosis subjects with PFT restrictive pattern contained a significantly lower percentage of lymphocytes (P = .004) and lower CD4/CD8 ratio (P = .03) compared with controls. In this subgroup, TLC also was negatively correlated with the neutrophil count (P = .043), and positive correlations were found between TLC and CD3 (P = .053), disease duration and CD4/CD8 ratio (P = .033), TLC and FVC and percentage macrophages (P = .033 and P = .052, respectively), diffusion per unit of alveolar volume, and percentage macrophages (P = .032), and C-reactive protein and percentage lymphocytes, percentage macrophages, and neutrophil count (P = .02, P = .008, and P = .006, respectively).

Induced sputum analysis of subjects with systemic sclerosis, including those with restrictive lung disease, shows changes in cellular pattern and correlation with several highly relevant clinical and PFT parameters.