Medical Laboratory Scientist (MLS) ASCP Practice Exam

A low leukocyte alkaline phosphatase (LAP) score is particularly associated with conditions such as Paroxysmal Nocturnal Hemoglobinuria (PNH) and Chronic Myeloid Leukemia (CML). In CML, the abnormal proliferation of myeloid cells contributes to a decreased activity of alkaline phosphatase, leading to low LAP scores. Similarly, in PNH, which involves a mutation in hematopoietic stem cells affecting the red blood cells and their susceptibility to hemolysis, there is significantly reduced LAP activity.

In contrast, conditions like Acute Lymphoblastic Leukemia (ALL) typically feature a different profile of enzyme activity. Parasite infections and reactive thrombocytosis may occur with normal or elevated LAP scores, as they generally involve a reactive increase in leukocytes which would not correspond with a low LAP reading. Thus, the association of low LAP scores with CML and PNH makes the selection of that answer a sound choice for understanding the hematological implications of these conditions.