Pulmonary function tests in sarcoidosis

Abnormalities in pulmonary function tests (PFTs) are present in approximately 20% of patients with radiographic stage I sarcoidosis and in 40% to 80% of patients with stages II, III, or IV (6,9,10,28,53,54). Reduced lung volumes [e.g.. 

Alterations in cardiopulmonary exercise tests (CPET) have been noted in 28% to 47% of patients with sarcoidosis (6,63,65,66). Typical findings include ventilatory limitation or increased dead space/tidal volume ratio (Vd/Vx) or widened alveolar-arterial O2 (A-a O2) gradient with exercise (63,65). CPET may be abnormal when static PFTs are normal (63,67). Exercise-induced desaturation correlated with reductions in DLco (63,68-70), whereas lung volumes and expiratory flow rates did not (70). 

Although CPET is more sensitive than static PFTs in predicting work and exercise capacity, the practical value of CPET is limited. Spirometry and oximetry are usually adequate to follow the course of the disease (6). For patients with more severe disease, noninvasive six-minute walk tests (6MWT) provide additional quantitative data. 

Honeycomb change is most often associated with restriction and low DLco. whereas bronchial distortion is often associated with reduced expiratory flow rates (45). Airflow obstruction may be suggested on CT when bronchial mural thickening, small-airway narrowing, or patchy air trapping is present (46,74,75). Reticular shadows and thickened bronchovascular bundles on HRCT were independently associated with lower FEVi/FVC ratio (57). 

CT patterns may evolve over time. Serial CT in 40 patients with pulmonary sarcoidosis showed several distinctive evolutionary patterns (76). Macroscopic nodules often disappeared or decreased in size at follow-up. Consolidation and GGO resolved in some patients, but evolved into honeycombing in other patients (associated with a decline in FVC). A conglomeration pattern shrank and evolved into bronchial distortion and a decline in FEVi/FVC ratio. 

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Suhramanian I, Flaherty K, Martinez F. Pulmonary function testing in sarcoidosis. In Baughman RP, ed. Sarcoidosis. New York Taylor and Francis Group, 2006 210 415 33. 

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