Plasma lactate dehydrogenase: a marker of disease activity in cryptogenic fibrosing alveolitis and extrinsic allergic alveolitis?

Total plasma lactate dehydrogenase (LDH) activity may be elevated in cryptogenic fibrosing alveolitis (CFA) and extrinsic allergic alveolitis (EAA), and may be a useful monitor of disease progress. In a retrospective, primary referral centre study, we compared LDH at presentation, prior to bronchoalveolar lavage BAL, and after treatment and follow-up with changes in pulmonary function, in patients with CFA, EAA and pulmonary sarcoidosis. Plasma levels of LDH at presentation in CFA (n = 47) and EAA (n = 10) were significantly higher than in patients with sarcoidosis (n = 36). LDH activity decreased in patients with improving lung function (EAA, p = 0.008; CFA, p = 0.02), whereas it increased in CFA patients with deteriorating lung function (p = 0.015). Total plasma LDH is a simple, though nonspecific test, which appears to reflect changes of disease activity in patients with CFA and EAA.