Pulmonary function tests: High rate of false-negative results in the early detection and screening of scleroderma-related interstitial lung disease

Objective Validated methods for the screening and early diagnosis of systemic sclerosis (SSc; scleroderma)-related interstitial lung disease (ILD) are needed. The aim of this study was to evaluate the performance of pulmonary function tests (PFTs) compared with that of high-resolution computed tomography (HRCT) of the chest for the detection of SSc-related ILD in clinical practice, and to identify predictors of lung involvement that is functionally occult but significant on HRCT. Methods Prospectively enrolled patients with SSc were assessed according to the European League Against Rheumatism (EULAR)/EULAR Scleroderma Trial and Research standards. The assessment included PFTs and HRCT. The HRCT images were evaluated in a blinded manner by 2 experienced radiologists. The performance parameters of PFTs for the diagnosis of SSc-related ILD were calculated. Predictors of significant ILD as determined by HRCT in patients with normal forced vital capacity (FVC) values were identified through logistic regression. Results Among the 102 patients, 64 (63.0%) showed significant ILD on HRCT, while only 27 (26.0%) had an FVC <80% of predicted, and 54 (53.0%) had a decrease in the results of at least 1 PFT. Forty (62.5%) of 64 patients with significant ILD on HRCT had a normal FVC value, translating into a high false-negative rate. Notably, 5 of 40 patients with a normal FVC value had severe, functionally occult lung fibrosis; in 2 of these patients, the results of all of the PFTs were within normal limits. Patients with normal FVC values despite evidence of fibrosis on HRCT more frequently had anti-Scl-70 antibodies and diffuse SSc and less frequently had anticentromere antibodies (ACAs) compared with patients with both normal FVC values and normal HRCT results. Conclusion The derived evidence-based data reveal a high risk of missing significant SSc-related ILD when relying solely on PFTs. More comprehensive screening algorithms for early detection are warranted. In particular, additional imaging investigations for the early detection of SSc-related ILD should be considered in ACA-negative patients with normal FVC values.