Forced vital capacity, or FVC, is defined as the amount of air that can be forcibly exhaled from the lungs after taking the deepest breath possible. Patients suffering from systemic sclerosis, or scleroderma (a chronic systemic autoimmune disease) often undergo this type of spirometry testing to assess their status of interstitial lung disease.

However, a group of researchers led by Dr Elizabeth Volkmann, a rheumatologist at the University of California, Los Angeles, have found evidence suggesting that a structural, physiologic, and patient-oriented composite outcome may be a more comprehensive measure of treatment response instead of FVC measurements for patients with systemic sclerosis and interstitial lung disease.