Biochemical and immunologic features of an outbreak of Legionnaires disease: comparative study between community-acquired pneumonias.

Legionella pneumophila has been recognized as an important cause of community- and hospital-acquired pneumonia. This study evaluates the interrelationship between that patients group with Legionnaires disease (LD) and the possible factors that may predispose hosts to acquire this infection. Likewise, we search for preliminary biochemical and immunologic evidences that could help physicians to differentiate between LD and other pneumonias. We analyzed biochemical parameters and immunoglobulin levels in 61 LD patients and a control group (n = 30) who were non-Legionella pneumonia diagnosed. We observed statistically significant differences in LD patients versus control group in serum sodium, albumin, gamma-band, IgG levels, (P < .01) and for total proteins, aspartate aminotransferase (AST), and lactate dehydrogenase (LDH) (P < .05). Our study shows a trend between the presence of LD and immunoglobulin deficiencies in the group studied. Deficit in IgG or IgG plus IgM, during the exposure period, may predispose individuals to suffer legionellosis (P < .05). Overall, hypoalbuminemia, hyponatremia, and high AST and LDH levels can represent a useful prognostic marker in patients with severe pulmonary infection suspected to be legionellosis.