[An improved method for biochemical measurement of the activity of neutrophil alkaline phosphatase and its application to myeloproliferative disorders].

The activity of neutrophil alkaline phosphatase (NAP) has been commonly measured semi-quantitatively by rating the intensity and number of positive granules on cytochemical staining. This method has been widely adopted because of quickness and simplicity. However, the scoring system, in itself, seems to have several demerits that it has poor reproducibility and has limit for expressing enhanced NAP activity. We improved previous methods for measuring biochemical activities of NAP. Our method was as quick and simple as cytochemical measurement and had more excellent reproducibility. Biochemical activities of NAP ("b-NAP"s) in extract from 2 x 10(6) neutrophils of 7 patients with polycythemia vera were about six times as high as those of 7 cases of essential thrombocythemia [144.8 +/- 33.2, 23.1 +/- 9.1 U, respectively], while NAP scores in the former showed only twice the degree of elevation of those in the latter. These observations suggest that our method can represent high NAP activity more exactly than NAP score and may be a potential tool in differentiating polycythemia vera from essential thrombocythemia.