Acetylcholinesterase, Erythrocytes

CPT CODE:

USEFUL FOR:

Detecting effects of remote (months) past exposure to organophosphatase inhibitors (insecticide poisoning)

SPECIMEN REQUIRED:

Submit only 1 of the following specimens:
Whole Blood to be Washed at Mayo Medical LaboratoriesHeparinized whole blood must arrive within 72 hours of draw.Note:   If specimen cannot arrive within 72 hours, please send washed                 erythrocytes.
Draw blood in a green-top (heparin) tube(s) from a fasting patient(4 hour preferred, nonfasting acceptable), and send 5 mL of heparinized whole blood refrigerated. Specimen cannot be frozen.Note:      1.  Draw date is required on request form for processing.                  2.  Include type of specimen sent (heparinized whole blood)                      on request form. 
If preferred, washed packed red blood cells will also be acceptedas follows:
Washed ErythrocytesDraw blood in a green-top (heparin) tube(s) from a fasting patient(4 hour preferred, nonfasting acceptable), and process 2 mLof heparinized whole blood as follows:1. Immediately centrifuge for 10 minutes at 650 x G.2. Discard the plasma and buffy coat layers.3. Add a cold 0.9% saline solution to the erythrocytes (about 2    times the volume of erythrocytes).4. Mix gently by inversion and centrifuge again for 10 minutes     at 650 x G.5. Remove and discard the saline.6. Repeat the wash steps (3-5) 2 more times.7. After the final centrifugation, remove and discard the saline    and a thin layer of the top cells.8. Immediately freeze the washed, packed cells (red cell pellet    from step 7), and send specimen frozen in a plastic vial.Note:      1.  Draw date is required on request form for processing.                  2.  Include type of specimen sent (washed packed red blood                       cells) on request form.

TRANSPORT TEMPERATURE:

VariesRefrig\Ambient NO\Frozen NO - Whole BloodFrozen\Refrig NO\Ambient NO - Washed Packed Red Blood Cells

CLINICAL INFORMATION:

Acetylcholinesterase (AChE) is anchored to the external surfaceof the red blood cell.  Its appearance in a lysate of red cells is diminished in paroxysmal nocturnal hemoglobinuria (PNH).  The use of red cell AChE for PNH has not gained widespread acceptance, and flow cytometry testing is most often used for PNH (see #81156 "PI Linked Antigen, Blood").
Red cell AChE is most often used to detect past exposure toorganophosphate insecticides with resultant inhibition of the enzyme.Both the pseudocholinesterase activity in serum and red cell AChE are inhibited by these insecticides, but they are dramatically different vis-a-vis the temporal aspect of the exposure.  The half-life of the pseudo-enzyme in serum is about 8 days, and the "true" cholinesterase (AChE) of red cells is over 3 months (determined by erythropoietic activity).  Prior exposure up to several weeks is determined by assay of the pseudo-enzyme and months after exposure by measurement of the red cell enzyme.  The effect of the specific insecticides may be important to know prior to testing.

CLINICAL INTERPRETATION:

Activities less than normal are suspect for exposure to certaininsecticides.

REFERENCE VALUES:

26.7-49.2 U/g of hemoglobin