Objective: To determine the ability of initial forced vital capacity (FVC) of patients with scleroderma to predict subsequent pulmonary function deterioration.
Methods: Data on 78 patients with scleroderma were retrospectively collected and analyzed. FVC (percent predicted), diffusing capacity for carbon monoxide (percent predicted), and various clinical and laboratory parameters were recorded. Pulmonary function decline (outcome) was defined as at least a 15-point sustained decrease in FVC (percent predicted). Kaplan-Meier analyses were performed separately for 60 patients initially assessed within the first 3 years from disease onset (group A) and 16 patients whose FVC values in the fourth or fifth year from disease onset were ascribed as baseline measurements (group B).
Results: Based on baseline FVC, patients in each group were categorized into those with normal FVC (> or =80% predicted) and those with decreased FVC (<80% predicted). In group A, the percent-predicted FVC of 89% of patients with normal initial FVC and of 75% of patients with reduced baseline FVC did not decrease by > or =15 points at 5 years (log rank P = 0.04). Four patients with decreased baseline FVC developed respiratory failure (FVC <50% predicted) versus none with normal initial FVC. Analysis of group B showed no difference between patients with normal baseline FVC and those with decreased FVC in the ability to further predict pulmonary function decline (log rank P = 0.13). Clinical and laboratory parameters (age, male sex, baseline diffusion capacity, anti-topoisomerase I, or duration of Raynaud's phenomenon preceding skin manifestations) were not associated with pulmonary function decline.
Conclusion: Measured within the first 3 years from disease onset, baseline FVC (percent predicted) may predict deterioration of pulmonary function in patients with scleroderma. Patients with normal pulmonary function at initial assessment are at low risk to develop considerable impairment of pulmonary function.