Detection of leukemic blasts in peripheral blood specimens by reverse transcriptase polymerase chain reaction assay...

The enzyme myeloperoxidase (MPO), an important constituent of granulocytes, is used clinically in the diagnosis and classification of acute leukemia. Whereas MPO protein or enzyme activity is detectable in mature granulocytes, MPO RNA is present only in myeloblasts or promyelocytes. Some undifferentiated, biphenotypic, or lymphoblastic leukemias, although lacking MPO enzyme activity, express low levels of MPO RNA, a fact that may be of prognostic and therapeutic importance. However, current methods are inadequate for reliably detecting low levels of MPO RNA in leukemic cells containing few copies of the message. We have developed a new and highly sensitive reverse transcriptase-polymerase chain reaction (RT-PCR) assay for detecting low levels of MPO RNA in peripheral blood specimens of leukemic patients. This report describes the assay, and demonstrates its potential applicability to the diagnosis and classification of acute leukemias.