Laboratory diagnosis of pleural effusion with special reference to pH
Hsu, C.Y.
Journal of the Formosan Medical Association 87(7): 736-741
1988
ISSN/ISBN: 0371-7682 PMID: 3249203 Document Number: 325124
From February 1983 to August 1986, 142 pleural effusion patients who underwent diagnostic thoracentesis were reviewed. The cause was undetermined in 25 cases (17.6%). There were 23 transudates and 94 exudates in the remaining 117 cases. Most of the pleural fluid pH values fell in the range between 7.20 and 7.50, including 22 of 23 transudative and 69 and 94 exudative pleural effusions. Lower pH values (< 7.20) could be found in tuberculosis, malignant effusion, parapneumonic effusion and hemopneumothorax. However, low pleural fluid pH had neither a diagnostic nor prognostic value in tuberculous and malignant pleural effusion. Parapneumonic effusion had the most frequent chance (15 out of 19 cases) to yield low-pH (< 7.20) pleural field. Pleural fluid complement levels (C3 and C4) were significantly lower in immunologic disorders than in tuberculous pleural effusion with 4.9 .+-. 3.5 mg/g protein vs 19.1 .+-. 7.5 mg/g protein for C3, and 1.8 .+-. 1.9 mg/g protein vs 6.5 .+-. 2.7 mg/g protein for C4, respectively (p < 0.05). In conclusion, measurement of pleural fluiid pH is not so useful as is recommended in the literature. However, measurement of pleural fluid complement levels (C3 and C4) may be helpful in the diagnosis of pleural effusion caused by immunologic disorders.