Why Is My Dog's M:E Ratio Abnormal ?

Why Is My Cat's M:E Ratio Abnormal ?

To see what normal blood and urine values are for your pet, go here

For an explanation of causes of most abnormal blood and urine tests go here

To see how tests are often grouped, go here

Ron Hines DVM PhD

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Your Pet's Myeloid To Erythroid Cell Ratio

M:E ratio, (Of A Bone Marrow Sample)

Your pets White Blood Cell (leukocyte) Count (=WBC or ~CBC) and red cell (erythrocyte) count are both the result of what is going on in its bone marrow.

The only white blood cells that didn’t originate in the dog or cat 's bone marrow are its lymphocytes - those were produced in its lymphatic tissues (lymph nodes, etc.); In dogs and cats, those are also the ones most likely to become cancerous.

When the laboratory reports back that your pet's circulating white blood cell numbers (WBCs) or their characteristics are unusual and the the pet's blood chemistry panel, physical exam and related procedures do not indicate the cause, your veterinarian might consider an M:E ratio test to be an appropriate next step.

That will be even more the case if cells that belong in the pet's bone marrow are found circulating around in the pet's blood. Examining what is going on in your pet’s bone marrow “factory” is a logical decision whenever that occurs.

Other specific reasons an M:E test might be ordered are unexplained (non-regenerative) anemia, unexplained bleeding, or a lack of one or more classes of white blood cells that should have been in your pet's blood CBC/WBC but weren't. An overabundance of a single cell type without a good explanation is another.

Repeated, unexplained fevers or infections, or a lack of expected response response to therapy might also indicate that an M:E test is desirable.

When veterinary pathologists examine bone marrow samples submitted by your veterinarian, they look for abnormalities in the "founding" cells (progenitor cells, myeloid cells, stem cells) that produce the white cells and the "founding" cells that produce red cells (erythroid cells, erythroid precursor cells). They also compare the number of each to the other, looking for an overabundance (too many) of any one type.

Reasons Why Your Pet’s Myeloid:Erythroid Ration Might Be Abnormal :

In mature and older pets, leukemia (cancer) of one of the cell lines in the marrow is a common cause. Those go by multiple names and some are pre-cancerous (hyperplastic) rather than cancerous states.

Some are: Myeloid leukemia, multiple myeloma, myelodysplastic syndrome (MDS), defective blood platelet production in cats (dysthrombopoiesis, often associated with feline leukemia virus), eosinophilic leukemia and myeloid metaplasia. Some have progressed to cancer, some will progress to cancer and some will never do so. How they progress is highly unpredictable.

Other factors that can cause an abnormal M:E ratio include: FIV infection in cats, parvovirus infection in dogs and cats with panleukopenia. Severe cases of Ehrlichia parasites in dogs or hemobartonella in cats and autoimmune diseases directed at the bone marrow can also affect the pet's M:E ratio.

Certain medications can affect your pet’s M:E ratios:
Those include trimethomprim/sulfa, chloramphenicol antibiotic or methimazole medication given to hyperthyroid cats. Albendazole wormer for intestinal parasites, phenobarbital for seizures, griseofulvin for ringworm fungus have also caused altered M:E ratios.

Giving estrogens to abort a pregnancy (the infamous mismate shot) or when the pet naturally produces too much estrogen will also alter M:E ratios.

Deficiencies in folate or vitamin B12 can also be the cause as can chronic blood loss anemia.

Gray collies with a condition called cyclic hematopoiesis and dogs with congenital (born with) dyserythropoeis, dogs with a rare condition of having too many red blood cells (polycythemia vera) all often have abnormal M:E ratios as well.

Complementary Tests :

A CBC/WBC should be obtained at same time the M:E is run. When CBC blood films are examined by a trained clinical pathologist’s eye, subtle changes in the white blood cells can help make the diagnosis. Cytochemical staining of marrow cells, immunohistochemistry tests

.................... DxMe