Leukocyte Alkaline Phosphatase (LAP) Score is valuable in the work-up of certain hematological diseases. Most notably, the score is decreased in Chronic Myelogenous Leukemia and Paraoxysmal Nocturnal Hemaglobinurea but increased in leukemoid reaction to infection and Polycythemia Vera. Last year we reported the LAP scores of 14 patients with Myelodysplastic Syndrome (MDS). Our results showed that patients with less than 5% bone marrow blasts had significantly higher LAP scores than patients with 5–19% bone marrow blasts. We raised the possibility that LAP scores decrease as MDS progresses (

Blood
, Nov
2006
;
108
:
4865
). In the present study we attempt to further evaluate the utility of LAP in MDS. In addition to our original cohort, bone marrow aspirate results and LAP scores were reviewed from 14 more patients with MDS, for a total of 28 patients. We again assessed the relationship of LAP to bone marrow blast percentage. Furthermore, we recorded a second LAP score, taken at a later date, from 16 of the 28 patients. For those patients with two LAP scores we compared the trend of LAP score to the interval activity of MDS, using transfusion requirement, complete blood cell count (CBC) and clinical assessment as markers of disease activity. In our analysis of LAP score relative to bone marrow blast percentage we again found a significant difference between patients with less than 5% blasts (n=8) and those with 5% to19% blasts (n=20). Patients with less than 5% blasts had significantly higher LAP scores (90.25 ± 18.27) than those with 5 to19% blasts (44.35 ± 52.09) (p<0.0048) (see charts 1 and 2). In our analysis of LAP score in relation to disease progression we found that among patients for whom LAP score decreased, 42.9% (3/7) had disease progression. In patients whose LAP score increased, 11.1% (1/9) had disease progression (p<0.2615) (chart 3). Overall, our results confirm that LAP scores do tend to be lower in patients with more severe disease, as assessed by bone marrow blast percentage. However, although a trend was observed toward change in LAP score correlating with disease activity this was not statistically significant, and larger prospective studies are necessary to assess whether LAP is an accurate marker of MDS progression.

Chart 1: LAP scores of patients 1 through 8 with bone marrow blasts less than 5% (mean 90.25, median 96) . / Chart 2: LAP scores for patients 1 through 20 with bone marrow blasts of 5% to 19% (mean 44.35, median 30)
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Chart 1: LAP scores of patients 1 through 8 with bone marrow blasts less than 5% (mean 90.25, median 96)

Chart 2: LAP scores for patients 1 through 20 with bone marrow blasts of 5% to 19% (mean 44.35, median 30)

Chart 1: LAP scores of patients 1 through 8 with bone marrow blasts less than 5% (mean 90.25, median 96) . / Chart 2: LAP scores for patients 1 through 20 with bone marrow blasts of 5% to 19% (mean 44.35, median 30)
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Chart 1: LAP scores of patients 1 through 8 with bone marrow blasts less than 5% (mean 90.25, median 96)

Chart 2: LAP scores for patients 1 through 20 with bone marrow blasts of 5% to 19% (mean 44.35, median 30)

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Chart 3: Percent of patients with disease progression among those with decrease in LAP score (white) and those with increase in LAP score (gray) (p<0.2615).
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Chart 3: Percent of patients with disease progression among those with decrease in LAP score (white) and those with increase in LAP score (gray) (p<0.2615).

Chart 3: Percent of patients with disease progression among those with decrease in LAP score (white) and those with increase in LAP score (gray) (p<0.2615).
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Chart 3: Percent of patients with disease progression among those with decrease in LAP score (white) and those with increase in LAP score (gray) (p<0.2615).

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Topics:
myelodysplastic syndrome, neutrophil alkaline phosphatase score measurement, disease progression, bone marrow aspiration, hematological diseases, infections, leukemia, myelocytic, chronic, leukemoid reaction, leukocyte alkaline phosphatase, polycythemia vera

Author notes

Disclosure: No relevant conflicts of interest to declare.

2007, The American Society of Hematology
2007
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