Adenosine deaminase activity and free IL-2 receptor levels in serum from patients with mycoplasma pneumonia.

Adenosine deaminase (ADA) activity and free interleukin (IL)-2 receptor levels were assayed in serum samples from patients with mycoplasma and bacterial pneumonia to evaluate the usefulness of these parameters in distinguishing between these diseases at an early stage. Serum ADA and free IL-2 receptor levels in patients with mycoplasma pneumonia (32.4 +/- 9.2 U/l, 960 +/- 204 U/ml) were significantly higher than those in patients with bacterial pneumonia (12.5 +/- 3.3 U/l, 425 +/- 86 U/ml) and in healthy controls (14.0 +/- 3.4 U/l, 286 +/- 49 U/ml) (p less than 0.001). Of the 20 mycoplasma pneumonia cases, 19 showed increased levels of ADA over 20.8 U/l; in 17 of the 19, the increase of ADA was seen before the elevation of the specific antibody to Mycoplasma pneumoniae. In contrast, serum ADA levels in all 20 cases of bacterial pneumonia were lower than 20.8 U/l. There results indicate that assays for serum ADA and free IL-2 receptor levels are useful in distinguishing between bacterial and mycoplasma pneumonia at an early stage.