Myeloperoxidase-deficient polymorphonuclear leucocytes. Longitudinal study during the preremission--and the remission phase in acute myeloid leukaemia. Comparison to neutrophil alkaline phosphatase (NAP) activity.

Serial determinations of MPO and NAP activities in granulocytes were performed during the preremission phase and the remission phase in patients with AML. Of 18 patients examined during the preremission period, 9 showed an increased number of MPO deficient PMN. Complete remission was attained in 4 of these, in 3 the number of abnormal granulocytes changed to normal 7, 7 and 14 days before and in 1 simultaneously with the attainment of complete remission. In the other patients no changes in granulocyte MPO activity occurred during the preremission period. All 20 patients examined during complete remission showed a normal MPO activity in granulocytes. Of eight patients, who at diagnosis had shown abnormal granulocyte MPO activity, three developed relapse. In two of these, an increased number of MPO deficient PMN reappeared two and eight months prior to and in one simultaneous with clinical and laboratory suspicion of relapse. A statistically significant relation between low NAP scores and an increased number of MPO deficient PMN was found (P = 0.011). Serial determinations of MPO activities in PMN, although restricted to cases of AML with initially abnormal values, may prove helpful in predicting achievement of complete remission and may furthermore prove to be useful as an indicator of early relapse.