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1298 Acanthocyte Acetylcholine Receptor Antibody Test

Acanthocyte
VetBooks.ir Definition

prepared, fresh blood films.
rule out specimen age artifact
Erythrocyte morphologic abnormality char- numbers of circulating acanthocytes on properly prepared when specimen was collected to help
acterized by irregularly spaced, usually blunt
projections from the normally smooth round Causes of Abnormally High Levels Relative Cost: $/$$ (depending on reflex
cell membrane with loss of normal erythrocyte Hemangiosarcoma; liver, splenic, or renal testing included in CBC panel)
central pallor (from the Greek akantha, meaning disease; artifact of blood film preparation
“thorn”). Pearls
Next Diagnostic Steps to Consider • Considered nonspecific and a common
Synonyms if Levels Are High artifact; should be evaluated in a second,
Burr cell, spur cell, echinoacanthocyte Repeat CBC to confirm; if consistent finding, fresh specimen before drawing diagnostic
evaluate for liver, splenic, or renal disease and conclusions.
Physiology metabolic abnormalities as suggested by clinical • Acanthocytes can be difficult to differentiate
Altered red blood cell shape may be an artifact signs. Evaluation of a saline preparation can help from crenation. Crenated erythrocytes have
of blood film preparation. True acanthocyte differentiate artifactual erythrocyte shape change regularly placed “tent-shaped” projections
morphology is associated with altered lipid from in vivo changes in erythrocyte shape. and retain an area of central pallor.
metabolism, sometimes due to liver disease,
resulting in abnormalities in the lipid structure Lab Artifacts AUTHOR: Sharon M. Dial, DVM, PhD, DACVP
EDITOR: Lois Roth-Johnson, DVM, PhD, DACVP
of the red blood cell membrane. Vascular disease Specimen age artifact (delay in preparing blood
(vasculitis, DIC) may also disrupt normal red film, sample not refrigerated); artifact of blood
blood cell shape. film preparation
Reference Interval Specimen Collection and Handling
Not reported unless seen on blood film. Healthy Whole blood in EDTA (lavender top tube) or
dogs and cats should not have appreciable heparin (green top tube); include a blood film

Acetylcholine Receptor Antibody Test

Definition Next Diagnostic Steps to Consider Important Interspecies Differences
Detection of serum autoantibodies aimed at if Levels Are High Acquired MG is more common in dogs than
skeletal muscle acetylcholine receptors (AChR). An increased value is considered confirmatory cats.
Used to confirm the presence of acquired for myasthenia gravis. Thoracic imaging is
myasthenia gravis (MG). recommended to assess for the presence of Drug Effects
a cranial mediastinal mass (thymoma associ- Recent immunosuppressive therapy can decrease
Synonym(s) ated MG) and to evaluate the patient for the titer, potentially causing a false-negative
MG test, AchRAb titer potential megaesophagus, a common problem result.
in MG patients. General health screening
Physiology and evaluation for other forms of neoplasia Lab Artifacts
Acetylcholine is used to transduce signals from coinciding with acquired MG may also be Lipemia and hemolysis may cause false-positive
nerves to skeletal muscle. Functional AChR on prudent (p. 668). results.
skeletal muscle (the post-synaptic membrane
in the neuromuscular junction) are necessary Next Diagnostic Steps to Consider Specimen Collection and Handling
for normal signal transduction. In acquired if Levels Are Low Serum, 2 mL (red top tube, separated from cells
(immune mediated) MG, autoantibodies deplete AChR antibody testing is the gold standard for as soon as possible) should be submitted with
AChR. An immunoprecipitation radioimmu- diagnosing MG. If the result is negative but MG a cold pack overnight. Fasting patient prior to
noassay is used to detect these autoantibodies. is still suspected clinically, consider retesting in blood draw is recommended to minimize risk
a few weeks. It is rare for acquired MG patients of lipemia. Serum is stable for testing up to a
Reference Interval to be seronegative. Repeating neuromuscular week at 2°C to 8°C, longer if frozen.
0-0.6 nmol/L in dogs, 0-0.3 nmol/L in cats examination, use of electrophysiologic testing,
and muscle biopsy can be considered if other Relative Cost: $$$
Causes of Abnormally High Levels neuromuscular disorders have not been satis-
High levels of AChR autoantibodies indicate factorily ruled out. AUTHOR: Angela Royal, DVM, MS, DACVP
EDITOR: Lois Roth-Johnson, DVM, PhD, DACVP
the patient has acquired MG.

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