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%”

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The 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. 
Blasts < 5% 91 76 88 103 116 71 90 
Blasts 5%–19% 16 45 30 42 5 2 46 
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The 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. 
Blasts < 5% 91 76 88 103 116 71 90 
Blasts 5%–19% 16 45 30 42 5 2 46 
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Topics:
blast cells, bone marrow, myelodysplastic syndrome, neutrophil alkaline phosphatase score measurement, refractory anemias, leukocyte alkaline phosphatase, refractory anemia with excess blasts, refractory anemia with sideroblasts, severity of illness, basic local alignment search tool

Disclosure: No relevant conflicts of interest to declare.

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2006, The American Society of Hematology
2006
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