Forced Vital Capacity Found To Be Inadequate When Assessing Scleroderma
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.
Dr. Volkmann and her team based their study on 158 U.S patients enrolled in the first Scleroderma Lung Study, run in 2000-2004 at 13 U.S. centers to compare treatment with oral cyclophosphamide against placebo in patients with active SSC and interstitial lung disease. From all 158 patients, 125 had a high-resolution CT (HRCT) scan at baseline and within these, 83 also had a HRCT scan after 12 months. This last group formed the basis for the latest analysis, which included 41 patients randomized to cyclophosphamide treatment and 42 randomized to placebo. The data, presented at the annual European Congress of Rheumatology, revealed that the more robust association in the analysis were Transition Dyspnea Index (TDI), the scleroderma modified Health Assessment Questionnaire Disability Index (HAQ-DI), and quantitative, serial assessment of HRCT images of the patient’s lungs, all three proving to be stronger and more comprehensive than FVC alone.
Dr. Volkmann said that “ many physicians rely solely on FVC for following patients, and I think this may not be the best measure. Now that we have great imaging options we should use them. And the strongest correlates [in the new analysis] were with the HAQ-DI, a measure of what patients can do, and the TDI, in which patients say how much their disease has progressed. They are both patient oriented and tell you how the patient is doing.”
A senior collaborator on the study, Dr. Daniel Furst, professor of rheumatology at UCLA, said that it was still early to completely drop FVC as a tool to assess systemic sclerosis patients, however it was definitely relevant to add the two patient-oriented questionnaires and HRCT imaging.
“Using all four of these tools is not being widely done right now in U.S. rheumatology practice and I really think it’s a step forward,” said Dr. Furst.
However, he also alerted that he would like to see evidence documenting this approach has a positive impact on patient outcomes.
Although the main goal in this analysis was to identify the best assessment of lung disease in systemic sclerosis patients enrolled in clinical trials, the findings can also have implications for managing patients with this disease in routine practice.