PLEURAL FLUID BETA-2-MICROGLOBULIN AND ANGIOTENSIN-CONVERTING ENZYME CONCENTRATIONS IN RHEUMATOID-ARTHRITIS AND TUBERCULOSIS

Concentrations of beta(2)-microglobulin (B2M) and angiotensin-converti ng enzyme (ACE) were measured in pleural fluid (Pi) and serum (S) of 3 64 patients with pleural effusions. Eleven patients had rheumatoid art hritis (RA), 36 verified tuberculosis(TB), 15 suspected TB, 120 cancer , 21 empyema, 34 pneumonia, 33 various defined diseases, 67 effusions of unknown aetiology and 27 congestive heart failure. The median conce ntrations of Pf-B2M and Pf-ACE were significantly higher in patients w ith RA than in patients with any other disease (p < 0.005). Tuberculou s effusions contained higher Pf-ACE concentrations than any other type of non-rheumatoid effusion (p < 0.05). With sensitivities of 91%, the specificity of Pf-B2M and Pf-ACE for the diagnosis of RA was 86% and 55%, respectively, Local cellular immune events probably account for t he abundance of B2M and ACE in rheumatoid and tuberculous pleural effu sions. Pf-B2M and Pf-ACE determinations may aid in the differentiation of rheumatoid and tuberculous pleurisy from other types of pleural di sease.