Are the pulmonary function tests and the markers of activity helpful to establish the prognosis of sarcoidosis?

The prognosis of sarcoidosis is difficult to establish. It depends mainly on the persistence of activity over time and the degree of functional impairment of the involved organs. The aim of this study was to analyze whether the pulmonary function tests and the more commonly used markers of activity, such as serum angiotensin-converting enzyme (SAGE) and gallium-67 scan, are helpful to evaluate the prognosis of sarcoidosis, besides the clinical data. Over a 14-year period (1974-1987), 209 patients were diagnosed as having sarcoidosis at the Bellvitge Hospital, a 1,000-bed teaching hospital in Barcelona, Spain. Clinical, radiological, pulmonary function tests, and activity markers (SAGE and gallium-67 scan) data at diagnosis were collected and classified as variables, and a definition of disease activity was established. One hundred sixteen patients were on follow-up, had all the variables available and were included in the statistical analysis. A Cox proportional-hazard regression model identified the following variables as independently influencing the persistence of activity over time: absence of erythema nodosum [risk ratio (RR) = 2.78; 95% confidence interval (CI): 1.48-5.18], age greater than or equal to 40 years (RR = 1.67; 95% CI: 1.008-1.04), SAGE level greater than or equal to mean + 2 SD U/ml (RR = 1.45; CI: 0.99-1.07), hyperglobulinemia (RR = 2.47; CI: 0.98-6.24), forced vital capacity < 80% predicted (RR = 2.17; CI: 0.97-4.85), and male sex (RR = 1.8; CI: 0.95-3.45). We conclude that the pulmonary function tests and the SAGE level but not the gallium scan are helpful to identify the factors predicting persistence of activity in sarcoidosis. Therefore, we recommend to add these tests to the initial clinical evaluation of patients with sarcoidosis in order to establish the prognosis and improve the therapeutic approach.