Alkaline Leukocyte Phosphatase

Alkaline leukocyte phosphatase (ALP; synonyms: alkaline granulocyte phosphatase, AGP; leukocyte AP; leukocyte alkaline phosphatase, LAP; neutrophil alkaline phosphatase, NAP) is an enzyme found in rod- and segment-nucleated neutrophil granulocytes, metamyelocytes (few), and in eosinophils (few) of blood and bone marrow. It catalyzes the hydrolysis of phosphoric acid esters in alkaline environments.

The process

Material needed

  • 2 air-dried blood smears (not older than one day).
  • Heparin blood

Normal values

ALP index: 10-100 points

Rating

ALP Index Rating
< 10 Decreased
20-100 normal
> 100 Increases

Indications

  • Suspected chronic myeloproliferative disorders or differentiation from chronic myeloid leukemia (CML).
  • Suspicion of cytopenias of the peripheral blood (aplastic anemias, agranulocytosis, leukemia, aleukemic forms).

Interpretation

Interpretation of increased values

  • Chronic myeloproliferative disorders:
    • Essential thrombocythemia (ET) – chronic myeloproliferative disorder (CMPE, CMPN) characterized by chronic elevation of platelets.
    • Osteomyelofibrosis (OMF; synonym: osteomyelosclerosis, PMS) – myeloproliferative syndrome; represents a progressive disease of the bone marrow.
    • Polycythaemia vera (PV, also called polycythemia or polycythemia) – rare myeloproliferative disorder in which all cells in the blood proliferate excessively (particularly affected are erythrocytes, and to a lesser extent platelets and leukocytes).
  • Leukemoid reaction
  • Bone marrow carcinosis
  • Pregnancy

Interpretation of lowered values

  • Chronic myeloid leukemia (CML; pathognomonic (evidence of disease) for the chronic phase of CML).
  • Immature myeloid leukemia
  • Paroxysmal nocturnal hemoglobinuria (PNH).
  • Sideroachrestic anemia – form of anemia in which there are increased sideroblasts in the bone marrow smear. These are the sign of impaired iron utilization, which leads to ineffective erythropoiesis (formation of mature erythrocytes (red blood cells) from hematopoietic stem cells of the hematopoietic bone marrow).