Measurements of M-subunit lactate dehydrogenase before therapy as an aid to tumour typing in serous effusions.

The levels of lactate dehydrogenase (LDH) isoenzymes were assayed in serous effusions from 111 hospital patients under investigation for cancer. The levels of M-subunit LDH in effusions from patients proven to have cancer were significantly higher than in patients in whom cancer was not proven (p less than 0.001). Chemotherapeutic agents used to combat cancer such as 5-fluorouracil, vincristine and cyclophosphamide are known to affect lactate dehydrogenase. On excluding these effects by studying patients before therapy was instituted, levels of M-subunit LDH were found to be significantly different for certain tumour types found in serous effusions, such as mesothelioma, adenocarcinoma and dedifferentiated carcinoma (p less than 0.005).