Pathology Associates Of Lexington, P.A.

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LAP lower normal range study report

To the e-mail report, below, Dr. Carter noted: Andrena, This is a good study, and thanks...Though I'm not sure that I agree w/ the final suggestion of "13-130".
Essentially the LAP score is an obsolete test, though still useful as an on-site proxy test for the Ph1 chromosome or the BCR/ABL mutation. On chromosome 9, the "abl" gene can translocate onto chromosome #22 at the "BCR" gene & make a "BCR/abl gene" mutation which then causes the cells to release tyrosine kinase which drives the stem cells to produce too many WBCs (95% of CMLs have this 9/22 translocation).

A morphologic review w/ pathologist sign-out for scores counted <20 is a good idea...and the work for a precise count >100 or 200 may be of doubtful usefulness. Do you think LAP scores are ever ordered for their high range?

The heparin tube requirement has a disadvantage of often requiring a new draw--not using the EDTA tube on hand. How variant were the EDTA scores?

I was prompted into this topic by a recent CML patient whose score was 15, which was interpreted by Dr. Madden's team as "Normal LAP score"--which it wasn't, of course. Then looking into it, you find "normal" low points from 0-33 w/ an average of 17.6--so really this is a false sense of precision at the low end.

Thus the morphologic correlated sign-out is probably optimal...Thanks, John Carter.

Dr. Carter (e-mail report to Dr. Carter 9/2/07),

We conducted a study of 20 normal individuals for LAP counts drawn in purple and green top tubes. Each sample was counted in duplicate by two different techs for a total of 80 counts, results as follows:

1. The purple and green top tubes study - 73% correlation
Recommendation - to use only green top tubes for LAP studies. A different normal range would be required for EDTA.

2. Reproducibility indicated a correlation of 92% which validated the results of the study. The EDTA results were not included for the

remainder of the study.

3. The normal results ranged from 15 to with a mean of 70.
Recommendation - Test results which fall within the range of 0-20 should be resulted by pathologist interpretation only (the score

may or may not be included in the interpretation). We currently report scores on all normal and high results with

low scores going back for pathologist interpretation after resulting. The lower normal range is very difficult to

establish as indicated in our study as well as when searching other sources. Here are a few examples or ranges

found: 0-160, 14-143, 25-130, 22-124, 33-149, 13-130, 20-100, 20-120, and 11-95. I think having a gray range of

0-20 will cover the patient with leukemia and a score 1-2 within the normal range.

I think we should leave the normal range as 13-130 with the range of 0-20 for pathologist interpretation.

Raw data and statistical analysis on file.

Andrena C. Wilson, MT (ASCP) SH
Hematology Specialist
Hematology Supervisor
Lexington Medical Center Laboratory
West Columbia, South Carolina 29169 (posted on website 1/19/08; latest addition 7/5/09)