Diagnostic value of ferritin, haptoglobin, alpha 1-antitrypsin, lactate dehydrogenase and complement factors C3 and C4 in pleural effusion differentiation

Searching to define diagnostic criteria for malignant and non-malignant pleural effusions, the differential diagnostic value of ferritin (FRT), haptoglobin (Hp), alpha 1-antitrypsin (alpha 1-AT), lactate dehydrogenase (LDH) and complement factors C3 and C4 were investigated prospectively in 100 consecutive patients with pleural effusions of various aetiologies. Pleural effusion FRT, C3 and C4 concentrations were found to be useful in differentiating exudates from transudates, so that transudates practically could be excluded in pleural effusion: serum FRT ratio lower than 0.5 and/or in pleural effusion values for C3 and C4 higher than 300 mg dl-1 and 70 mg dl-1, respectively. A pleural effusion: serum C3 ratio greater than 2 is seen only in malignant effusions. No discriminative pleural: serum ratio could be found in FRT and C4 values capable of differentiating malignant from non-malignant effusions. Pleural effusion alpha 1-AT and LDH values were elevated in exudates, as compared with transudates, and had an excellent sensitivity and predictive value, but low specificity, in differentiating malignant from non-malignant effusions. Finally, the sensitivity, specificity and positive predictive value of pleural effusion Hp concentrations were lower than those of FRT and complement factors C3 and C4, respectively.