Increase of lung transfer factor in early sarcoidosis

Dynamic spirometry and the lung transfer factor for CO (TLCO) were determined in 41 non-smoking patients with sarcoidosis before and after steroid treatment. Dynamic spirometry revealed usual stage-dependent restrictive and/or obstructive abnormalities; only maximal expiratory flow rate at 75% FVC (MEF75) was significantly increased after steroid treatment in stage 2 patients. The new finding is that TLCO was increased in stage 1 [on average 21% above the predicted values (p.v.)], but it was decreased in stage 2 (11% below p.v.) and stage 3 (27% below p.v.). The increase in TLCO in stage 1 was predominantly caused by an increase in TLCO membrane component (Dm) (33% above p.v.), while the pulmonary capillary blood volume (Vc') increased less (19% above p.v.). Steroid treatment significantly reduced TLCO, Dm and Vc' in stage 1 (for 14, 17 and 18% of the respective baseline values), whereas it caused TLCO and Dm increases in stage 2 (for 8 and 10% of the respective baseline values). In conclusion, a TLCO in pulmonary sarcoidosis may not only be decreased in its advanced stages, but also exhibit increased values, which appeared related to the subclinical inflammatory reaction in the stage 1 patients.