Exhaled nitric oxide is elevated in patients with progressive systemic sclerosis without interstitial lung disease

Background: Progressive systemic sclerosis (PSS) is a multisystem disorder of unknown etiology. Interstitial lung disease (ILD) is a major cause of mo rtality in this condition, and a major challenge in this regard is to ident ify parameters that would predict the onset or progression of ILD in patien ts with PSS. Abnormal cellularity of BAL fluid (BALF) has been demonstrated in patients with PSS without ILD. Study objectives: We investigated exhaled nitric oxide (NO) as a noninvasiv e marker of pulmonary inflammation in patients with PSS with and without cl inical and radiologic evidence of ILD. This was compared with the cellulari ty of BALF. Our hyothesis was that exhaled NO was elevated in patients with PSS without ILD who had abnormal BALF cellularity. Setting: Pulmonology and rheumatology units of a university-based, tertiary referral hospital in Durban, South Africa. Study methods: Exhaled NO was measured using a chemiluminescence analyzer i n 12 patients with PSS and ILD and in 12 patients without clinical or radio logic evidence of ILD and in 30 healthy control subjects. BAL, was pet-form ed in patients with PSS with and without the presence of ILD and in six hea lthy control subjects. Results: Subclinical inflammation was confirmed by increased inflammatory c ell counts in BALF from patients with PSS without ILD. Exhaled NO (mean [SE M]) was elevated in patients with PSS without ILD at 9.6 (0.7) parts per bi llion (ppb) compared to patients with PSS and ILD at 6.2 (0.6) ppb (p < 0.0 01) and healthy control subjects at 6.3 (0.2) ppb (p < 0.001). Conclusion: Exhaled NO may therefore be an important noninvasive surrogate marker of in flammation in patients with PSS without ILD.