Predicting Lung Function Decline with Serum Pneumoproteins: A Case Control Study

Introduction: Predictors of lung function decline in systemic sclerosis (SSc) are unknown. Serum pneumoprotein levels, surfactant protein-D (SP-D) and Krebs von den Lungen-6 (KL-6), correlate with pulmonary damage. We aimed to test whether levels can predict rapid lung function decline in SSc. Methods: SSc patients who had serial pulmonary function tests (PFT) were analyzed for SP-D and KL-6 levels by enzyme linked immunosorbent assay. Levels were correlated with an annual rate of decline in % predicted forced vital capacity (FVC) of >﹣2% (out-come); controls did not experience this FVC decline. Uni- and multi-variate analysis, adjusting for age, disease duration, gender, baseline % predicted FVC, SP-D, and KL-6, was performed. Results are reported as mean ± SD. Results: Thirty three cases and 25 controls had a disease duration of 8.8 ± 7.3 and 8.3 ± 6.1 years, respectively. In adjusted analyses, lung function decline correlated with greater baseline FVC OR = 1.03 [95% CI of 1.00-1.07]; a trend towards significance was observed for greater levels of SP-D with FVC decline, OR = 1.37 [95% CI of 0.96-2.12]. Conclusion: Our data provide evidence that SSc patients with long-standing disease are still at risk for lung function decline and SP-D levels may predict lung function decline.