Community-acquired pneumonia: serum adenosine-deaminase activity in the aetiological diagnosis

Adenosine deaminase (ADA) is a cytoplasmic enzyme which activity is increased in disorders that stimulate cells involved in the immune system. In community-acquired pneumonia (CAP), increased levels of serum ADA have been associated with the presence of atypical microorganisms as the source of the former. Previous studies have shown ADA increases in non-infectious diseases. We evaluated the factors that may influence plasmatic ADA (ADAp) levels in CAP patients. A study with cases (245 episodes of CAP) and controls (49) was designed, and the differences in ADAp activity with regard to organisms, comorbidity factors and complications were analyzed. A logistic regression analysis was performed. CAP caused by atypical microorganisms were found to have increased ADAp values. Variables that independently increased ADAp levels were: atypical etiology (OR = 5.9), liver disease (OR = 5.8), diabetes mellitus (OR = 1.9), and prior antibiotic consumption (OR = 1.7). ADAp is an etiologic marker that could be useful in the empiric approach of the treatment of CAP.