Assessing the Performance of Pulmonary Function Tests for Detection of ILD in Diffuse Cutaneous SSc

Pulmonary function tests alone are an inadequate screening tool for the detection of interstitial lung disease (ILD) in patients with early diffuse cutaneous systemic sclerosis (dcSSc), according to study results published in Arthritis & Rheumatology. Investigators suggested the concurrent use of high-resolution computed tomography (HRCT) to identify ILD in patients with dcSSc.

To assess the performance of pulmonary function tests in identifying ILD in patients with dcSSc, the investigators extracted data from the Prospective Registry of Early Systemic Sclerosis (PRESS), a multicenter, prospective cohort study of patients with dcSSc enrolled at 11 academic medical centers in the United States.

The present analysis included data from participants enrolled in the PRESS cohort study who underwent pulmonary function tests, spirometry, and HRCT between 2012 and 2019. Expert thoracic radiologists visually inspected HRCT for features of ILD; a positive HRCT result was considered as definitive evidence for ILD. Results from pulmonary function tests were compared with results from HRCT, and the sensitivity and specificity for ILD were calculated for each parameter of the pulmonary function tests, including forced vital capacity (FVC), total lung capacity (TLC), and diffusing capacity for carbon monoxide (DLCO).

Data from 212 patients were included in analyses. Mean patient age was 51.7±13.8 years, and 67.9% of the patients were women. Mean disease duration was 1.2±0.7 years at study enrollment. Mean FVC, TLC, and DLCO were 80.4±18.8%, 86.7±20.4%, and 68.4±24.4% predicted, respectively. Overall, 115 patients (54.2%) had evidence of ILD on radiography, including ground glass opacities, reticular changes, and/or honeycombing. Among these patients with radiographic evidence of ILD, 72 had an FVC <80%. With a sensitivity of 63%, FVC <80% alone was an inadequate predictor of ILD. Combining FVC <80% with DLCO <80% predicted improved sensitivity for ILD to 85%. Negative predictive value for these combined characteristics was 70%, and specificity was 42%. The addition of TLC to these parameters did not improve test sensitivity. Mean time between pulmonary function test and HRCT was 0.3±0.4 years.

According to these data, FVC <80% and DLCO <80% predicted outperformed any individual pulmonary function test parameter in identifying ILD. However, with a sensitivity of 85%, these combined parameters had a substantial false negative rate of 15%.

“We therefore recommend that all patients with dcSSc undergo baseline HRCT, in addition to [pulmonary function tests], to screen for ILD,” the investigators wrote.

Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.

Reference

Bernstein EJ, Jaafar S, Assassi S, et al. Performance characteristics of pulmonary function tests for the detection of interstitial lung disease in adults with early diffuse cutaneous systemic sclerosis [published online June 25, 2020]. Arthritis Rheumatol. doi:10.1002/art.41415