[Pleural effusion in rheumatoid arthritis (R.A.). Biochemical study of the pleural fluid (author's transl)].

The diagnosis of pleural effusion in R.A. is largely done by exclusion. Histopathological data, obtained by pleural punch-biopsy, are unreliable. It is generally a serofibrinous pleural effusion. Biochemical study of the pleural fluid shows a high protein level (> 40 g/l), high latex factor (larger than or equal to 1/2560) and, predominantly, low sugar rate in pleural fluid (< 0,35 g/l) and low complement level (whole hemolytic complement C3 and C4).