BACKGROUND: Lung involvement occurs in over 95% of sarcoidosis cases. The World Association of Sarcoidosis and Other Granulomatous Disorders (WASOG) organ assessment tool does not assign the likelihood of lung involvement based on Pulmonary Function Testing (PFT). Clinical characteristics linked to normal and abnormal physiologic pattern on PFT's in sarcoidosis are incompletely understood.
RESEARCH QUESTION: What is the frequency of obstructive physiology (OP), restrictive physiology (RP) or normal physiology in sarcoidosis patients and are there laboratory parameters linked to these different patterns?
STUDY DESIGN AND METHODS: We evaluated 253 sarcoidosis patients by their PFT findings and grouped them into OP, RP, and normal spirometry. We correlated these PFTs to demographic, clinical, and laboratory parameters. In some cases, we correlated the PFT abnormalities with proteins in the Olink metabolic and immune response protein panels.
RESULTS: Of the 253 cases studied, 64% had normal spirometry, 20% had OP, and 15% had RP. Abnormal PFTs were more frequent in males with 61.2% of the OP group and 82.1% of the RP group (p=0.002). The average lymphocyte percentage was lower in OP vs. RP (normal: 21.5%, OP: 17.3%, RP: 23.7%, p =0.04), sIL-2R was lower in OP vs normal (normal:632.1, OP 335.5, RP:563.4, p =0.026) and CRP was lower in OP vs RP, and in normal vs RP (normal:11.7, OP 8.2, RP:35.6, p =0.018). Those with RP had less splenic involvement (normal: 21.5%, OP 21.6%, RP: 2.6%, P=0.008). Five Immune Response proteins had differential abundance in the three comparison groups.
INTERPRETATION: Most of our sarcoidosis cohort has normal spirometry. When abnormal, OP was more common than RP. There may be a difference in immune mechanisms in those with OP compared to those with RP or normal spirometry. Continued comprehensive assessments of serum proteins may identify biomarkers to identify physiologic abnormalities and guide management.
