A patient has a leukocyte alkaline phosphatase score of 9. The ...

[lb_gilbert]

A patient has a leukocyte alkaline phosphatase score of 9. The positive control is 5. Select the correct interpretation.
 
  a. Chronic myelogenous leukemia
  b. Acute lymphocytic leukemia
  c. Polycythemia vera
  d. Test must be repeated

Question 2

A myeloperoxidase stain is performed on peripheral blood cells of a patient with acute leukemia and 85 blasts; the patient has an occasional mature neutrophil.
 
  When the stained slide is evaluated, the blasts are all negative but the mature neutrophils are strongly positive. What is the significance of this finding?
 
  a. The stain worked (internal positive control).
  b. Nothing can be determined until a positive control is also examined.
  c. Nothing can be determined because mature neutrophils are always positive.
  d. Nothing can be determined because only examination of the blasts is useful.

[Dominic]

Answer to Question 1

ANS: D
Positive controls should always be run with any cytochemical stain to assure that the stain worked. The positive control in this case is essentially negative (score of 5), so the stain must be repeated.

Answer to Question 2

ANS: A
The finding of positive neutrophils on the slide serves as an internal quality control to validate that the stain worked. If only blasts had been present (no mature neutrophils), and they were all negative, it would be crucial to examine the positive control stained at the same time before a negative result in the blasts would be significant. Proof that the staining was successful must exist before any result on blasts has meaning.