Leukocyte alkaline phosphatase

[Phloston]

I'm a bit confused as to when leukocyte alkaline phosphatase should be elevated vs reduced.

I just got a question on Kaplan QBank where it was very explicit in the vignette: "...leukocyte alkaline phosphatase is elevated..." Then it asked for the diagnosis.

The answer was CML.

Meanwhile, I specifically didn't answer that because I had read on Wikipedia some time ago (yes, I know that sounds ridiculous to cite Wiki as a reliable source) that LAP is reduced in CML, AML and PNH.

However, when I had seen that on Wiki, the following source was cited, so I thought it was reliable:

Ian M. Hann; Owen P. Smith (26 September 2006). Pediatric hematology. Wiley-Blackwell. pp. 763–. ISBN 978-1-4051-3400-2. Retrieved 5 November 2010.

I'd appreciate anyone's thoughts...

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[ijn]

Sounds like Kaplan might be wrong.

The leukocyte alkaline phosphatase (LAP) score, which is high in infection, inflammation, and polycythemia vera (PV) and low in chronic myeloid leukemia (CML) and paroxysmal nocturnal hemoglobinuria, may also be of help. It must be kept in mind, however, that the LAP score can be normal in PV and CML, particularly juvenile CML. Normal ranges for the LAP vary among laboratories; results may be unreliable in laboratories with minimal experience in performing the test.

LAP can be normal and still be CML, but I can't find anything to support a high LAP with CML unless the person has a secondary infection. What else was in the prompt?

 

[Phloston]

Sounds like Kaplan might be wrong.



LAP can be normal and still be CML, but I can't find anything to support a high LAP with CML unless the person has a secondary infection. What else was in the prompt?

The vignette mentioned something along the lines of 45M with 65% haematocrit and elevated LAP. That was it.

For CML, I thought the age was a little young and that we'd expect increased neutrophils, basophils and metamyelocytes (I assumed the increased metamyelocytes would correspond to increased haematocrit; is that correct?), but the high LAP threw me so I was like, "this can't be CML...this must be some sort of trick..."

 

[KillaCam]

Yeah I agree it must be wrong in Kaplan. LAP levels are often used as a differential diagnosis between CML and Leukamoid reactions, with LAP low in CML (more immature) and Leukamoid (more mature) being normal/higher than CML..........This is straight out of FA and everywhere else I have read

 

[Phloston]

I've done ~1200 questions from their QBank so far and I've found at least 20 errors. I had also found one this morning in one of their cardiac physiology graphs, which was outright appalling, and I am yet to have discovered a box where I can submit comments. I've literally been shocked by some of the mistakes they've made.

The worst part is I believe I've picked up on quite a few of these errors only because I've done so many questions already. I would be scared for a fresh MS2 do go through this QBank thinking that everything in there is to be taken with conviction.

 

[Dallas]

Told ya, kaplan qbank sucks.
Anyway, Goljan says LAP is low in CML.

 

[islandCrazy]

Funny because in Kaplan HY lectures they spend some time making sure you understand that LAP is not elevated in CML.

 

[OberynMartell]

Told ya, kaplan qbank sucks.
Anyway, Goljan says LAP is low in CML.

Pathoma says the same, "negative LAP stain..."

 

[HelpPleaseMD]

kaplan is definitely wrong in this.

I have a follow up question. Does a high leukocyte alkaline phosphatase add to the alkaline phosphatase levels measured in labs?

 

[ugetwutugiv]

I was JUST thinking that when I did this question yesterday! I spent 10 minutes trying to figure it out and freaking because my final is in two days.

Pulled up the question, and it turns out that the patient HAS polycythemia vera. The question was asking which of the following is most related to PV.

The choices are CML, multiple myeloma, sickle-cell, B12 deficiency, and warm antibody autoimmune hemolytic anemia.

So while CML does have low LAP, it is indeed related to polycythemia vera because both are proliferation of mature myeloid cells. CML = granulocytes, PV = RBCs