LS/MWLS/MW

MT 417 – Clinical Hematology IIManual/Special Tests Unit

Leukocyte Alkaline Phosphatase Exercise

LAP Questions KEY

LS/MWLS/MW

1. What is the main reason this stain is performed?

Mainly done to differentiate CML and leukemoid reactions caused by a severe bacterial infection; both are characterized by a neutrophilic leukocytosis.

The LAP is also used to help differentiate chronic myeloproliferative disorders (PV, MMM, ET, CML), differ polycythemias (primary versus secondary type) and monitor remission.

LS/MWLS/MW

2. What is an acceptable patient specimen?

Blood drawn from a woman in her third trimester of pregnancy or within 2 days post-partum.

3. What control is used?

Fingerstick blood smears are best but fresh, heparinized blood is most often used. EDTA anticoagulated blood is not acceptable because enzyme activity may be inhibited. Thin slides are made and must be fixed within 8 hours of blood collection.

Note: The LAP stain is NOT done on bone marrow smears.

LS/MWLS/MW

4. List in correct order the following LAP procedure steps:

Incubate slides in staining substrate solution

Fix smears within specified time limit

Count patient slide

Prepare patient & control smears

Validate control slide

Counterstain smears

3

2

1

4

5

6

LS/MWLS/MW

5. Which cells stain positive?Neutrophilic leukocytes are positive, staining from a pale pink to a deep red color (color depends on type of salt used).

Detects activity of the enzyme alkaline phosphatase, pH 8.6, in the cytoplasm of neutrophils (secondary granules/membrane associated). The amount of dye precipitated is proportional to the amount of enzyme present. Generally, a high WBC with increased neutrophils is associated with increased enzyme.

5. What is being detected?

LS/MWLS/MW

6. How are the cells graded?One hundred consecutive band & segmented neutrophils are rated 0-4+ on the basis of the quantity & intensity of the precipitated red dye in their cytoplasm.

A normal LAP score is 13-130 (established by institution). Healthy individuals have a normal score.

6. What is a normal score?

The sum of the ratings of 100 cells is the LAP score; the cell ratings and total score are reported.

LS/MWLS/MW

7. On the LAP control slide, cells were rated as follows:

0 20 =

1+ 60 =

2+ 20 =

What is your next step? (Select one)a. Count the patient LAP slide.b. Repeat stain with a new control and fresh

reagents.The control score is not within the acceptable range (>140) for this procedure. Check that procedure protocol was followed.

0

6040

Total LAP score = 100

LS/MWLS/MW

8. State the expected LAP score (Increased, Decreased, or Normal) for the following conditions:

Primary polycythemia

Secondary polycythemia

CML and Hodgkin’s lymphoma in remission

Paroxysmal nocturnal hemoglobinuria

Bacterial septicemia

Late pregnancy

N

N

I

D

I

I

LS/MWLS/MW

9. A STAT LAP is ordered on a 5-year-old male with a WBC of 8.5 K/µL and a differential of 20 segs-5 bands-70 lymphs-5 monos. Should you question this order?

An LAP does not appear to be indicated. The CBC/diff results are normal for a 5-year-old. The leukocyte alkaline phosphatase order should probably be an alkaline phosphatase order.

LS/MWLS/MW

You are now ready to perform a Leukocyte Alkaline Phosphatase

count/interpretation on the case slides provided and report your results on the lavender worksheet found in the Special

Tests Unit of the Hemo II manual.