Performance of Forced Vital Capacity and Lung Diffusion Cutpoints for Associated Radiographic Interstitial Lung Disease in Systemic Sclerosis

J Rheumatol. 2018 Nov;45(11):1572-1576. doi: 10.3899/jrheum.171362. Epub 2018 Oct 1.


Objective: Forced vital capacity (FVC) and DLCO are used for screening of systemic sclerosis-associated interstitial lung disease (SSc-ILD). The study purpose was to determine the sensitivity, specificity, and negative predictive value (NPV) (proportion of true negative screening tests) of FVC and DLCO thresholds for SSc-ILD on chest high-resolution computed tomography (HRCT) scans.

Methods: Patients fulfilling American College of Rheumatology 2013 SSc criteria with a chest HRCT scan and pulmonary function tests (PFT) were studied. A thoracic radiologist quantified radiographic ILD. Optimal FVC and DLCO % predicted thresholds for ILD were identified using receiver-operating characteristic curves. The FVC and DLCO combinations with greatest sensitivity and specificity were also determined. Subanalysis was performed in patients with positive Scl-70 autoantibodies.

Results: The study included 265 patients. Of 188 (71%) with radiographic ILD, 59 (31%) had "normal" FVC (≥ 80% predicted), and 65 out of 151 (43%) had "normal" DLCO (≥ 60% predicted). FVC < 80% (sensitivity 0.69, specificity 0.73), and DLCO < 62% (sensitivity 0.60, specificity 0.70) were optimal thresholds for radiographic SSc-ILD. All FVC and DLCO threshold combinations evaluated had NPV < 0.70. The NPV for radiographic ILD for FVC < 80% was lower in patients with positive Scl-70 autoantibody (NPV = 0.05) compared to negative Scl-70 autoantibody (NPV = 0.57).

Conclusion: Radiographic ILD is prevalent in SSc despite "normal" PFT. No % predicted FVC or DLCO threshold combinations yielded high NPV for SSc-ILD screening. "Normal" FVC and DLCO in patients with SSc, especially those with positive Scl-70 autoantibodies, should not obviate consideration of HRCT for ILD evaluation.


MeSH terms

  • Adult
  • Female
  • Humans
  • Lung / diagnostic imaging
  • Lung / physiopathology*
  • Lung Diseases, Interstitial / diagnostic imaging
  • Lung Diseases, Interstitial / etiology
  • Lung Diseases, Interstitial / physiopathology*
  • Male
  • Middle Aged
  • Predictive Value of Tests
  • Radiography, Thoracic
  • Scleroderma, Systemic / complications
  • Scleroderma, Systemic / diagnostic imaging
  • Scleroderma, Systemic / physiopathology*
  • Sensitivity and Specificity
  • Tomography, X-Ray Computed
  • Vital Capacity / physiology*