Leukocyte Alkaline Phosphatase Score in Myelodysplastic Syndrome: A Comparison of Patients with Normal and Abnormal Proportions of Bone Marrow Blasts.

Abstract

The expression of leukocyte alkaline phosphatase (LAP) in neutrophils has been shown to be reduced in some patients with myelodysplastic syndrome (MDS), but increased in the refractory anemia (RA) subtype. We performed a retrospective study looking at the LAP scores of 14 patients with MDS. Patients were grouped according to bone marrow blast percentage. Those with less than 5% blasts in the marrow (refractory anemia and refractory anemia with ringed sideroblasts) comprised one group (n=7) and those with 5% to 19% blasts (refractory anemia with excess blasts) comprised a second group (n=7). LAP scores in the group with fewer than 5% blasts were significantly higher (range 71 to 116, mean 93.6) than LAP scores in the 5%–19% group (range 2 to 46, mean 26.6) (p<0.0001). Our results suggest that LAP score may correlate with disease severity in MDS. If this finding is confirmed in larger prospective studies then LAP score may be a useful, relatively non-invasive aide in assessing the course and progression of myelodysplastic syndrome.LAP Scores for Patients 1 through 7 in the Groups “Marrow Blasts <5%” and “Marrow Blasts 5%–19%”1234567Blasts < 5%9176881031167190Blasts 5%–19%164530425246The LAP scores of the two groups differed significantly (p<0.0001). The mean for the “Blasts<5%” group was 93.6 (SD=16.9), and the mean of the “Blasts 5%–19%” group was 26.6 (SD=7.1). There was no crossover between groups, in that the lowest LAP score in the <5% group was 25 points higher than the highest LAP score in the 5%–19% group.