Beta2Microglobulin in Pleural Effusions

. Beta2microglobulin (β2m) concentrations in serum and pleural fluid from 64 patients with pleural effusion were studied. The level of β2m in pleural fluid was generally twice that in serum. The ratio of pleural fluid β2m to serum β2m in patient groups defined according to the final diagnosis showed an interestingly high value in tuberculous pleuritis and in patients with rheumatoid arthritis with pleural effusion. There was a positive correlation between the β2m and lysozyme contents in pleural fluid, suggesting local and simultaneous activation of different cell lines when the pleura is involved. We suggest that pleural fluid and concomitant serum β2m measurements should be taken into consideration when pleural effusion of tuberculous origin is suspected. Furthermore, β2m determination might help to differentiate between rheumatoid pleural fluid and pleural involvement due to other systemic diseases.