The diagnostic value of the serum lactic dehydrogenase determination in the evaluation of unexplained thrombocytosis.

Thrombocytosis may reflect a primary myeloproliferative disorder or be a secondary reaction to other pathologic processes. Patients with persistent unexplained thrombocytosis meeting criteria of primary thrombocythemia had elevated levels of serum lactic dehydrogenase, whereas comparable patients with secondary thrombocytosis did not. The findings of an elevated serum lactic dehydrogenase supports the diagnosis of a myeloproliferative syndrome in patients who have unexplained thrombocytosis, and should be useful in the differential diagnosis of this hematologic abnormality.