DIAGNOSTIC-VALUE OF LACTATE-DEHYDROGENASE ISOENZYME PATTERN IN PLEURAL EFFUSIONS

Lactate dehydrogenase isoenzymes have been used to classify the nature of pleural effusion. Nevertheless, studies have reported conflicting results. The objective of this study was to evaluate the diagnostic va lue of lactate dehydrogenase isoenzymes in the analysis of pleural eff usions. Pleural fluid samples obtained from three respective diagnosti c groups: group I transudate (n = 23), group n para-pneumonic effusion (n = 29) and group III malignant effusion or pleuritis carcinomatosa (n = 41) were evaluated. Total lactate dehydrogenase activity and lact ate dehydrogenase (LDH) isoenzyme pattern were significantly different between transudative (group I) and exudative (group II and III) effus ions. Group II and III showed a low percentage of LDH1 (p < 0.001), wh ereas the percentages of LDH4 (p < 0.001) and LDH5 (p < 0.001) were hi gher compared to group I. Moreover, in exudative effusions the percent age of LDH1 (p < 0.005), LDH4 (p < 0.005), as well as LDH5 (p < 0.005) were significantly different between parapneumonic and malignant effu sions. In contrast to relative lactate dehydrogenase isoenzyme values, the absolute values of lactate dehydrogenase isoenzymes did not diffe r between group II and group III. Logistic regression analysis yielded a strong discrimination between group I and II+III, simultaneously us ing lactate dehydrogenase, glucose and protein as explanatory variable s. Logistic regression analysis yielded only a weak discrimination bet ween group II and III, simultaneously using lactate dehydrogenase, glu cose and the absolute values of LDH2 and LDH4 as explanatory variables . In conclusion, the lactate dehydrogenase isoenzyme pattern differed between pleural effusions of transudative and exudative origin. Howeve r, including lactate dehydrogenase isoenzyme activities in the biochem ical work-up of pleural effusions did not reveal an additional discrim inatory value in the assessment of the classification of these effusio ns.