7. Lab Evaluation of Erythrocytes: Indices, Coombs, Methemoglobin, Iron

What would be the reasons for low HCT and low TPP?

S
O

• substantial ongoing or recent blood loss

• overhydration

What would be the reasons for low HCT and normal TPP?

I
D
C

• increased erythrocyte destruction

• decreased erythrocyte production

• chronic hemorrhage

What would be reasons for low HCT and high TPP?

A
M
L

• anemia of inflammatory disease

• multiple myeloma

• lymphoproliferative disease

What would be reasons for normal HCT and low TPP?

G
P
L

• GI protein loss

• proteinuria

• liver disease

What would be reasons for normal HCT and normal TPP?

nothing, this is normal

What would be reasons for normal HCT and high TPP?

I
D

• increased globulin synthesis

• dehydration masked anemia

What would be reasons for high HCT and low TPP?

protein loss combined with relative or absolute erythrocytosis

What would be reasons for high HCT and normal TPP?

S
A
D

• splenic contraction

• absolute erythrocytosis

• dehydration masked hypoproteinemia

What would be reasons for high HCT and high TPP?

dehydration

average volume of a single erythrocyte determined directly in hematology analyzers but determined by manual calculation for camelids and non-mammals

MCV

How do you calculate MCV?

MCV = (HCT / RBC count) X 10

average amount of hemoglobin in a single RBC that is determined by calculation but is not generally useful

MCH

What does MCH depend on?

erythrocyte size and internal hemoglobin concentration

When is MCH lowest?

with iron deficiency when MCV and MCHC are low

How do you calculate MCH?

MCH =(Hb / RBC count) X 10

value that is determined by calculation and is reported as g/dL of packed erythrocytes

MCHC (mean cell hemoglobin concentration)

How do you calculate MCHC?

MCHC = (Hb / HCT) X 100

When is macrocytosis (high MCV) commonly seen? Especially what type?

regenerative anemia; hemolytic anemia

When is it common to see macrocytosis in cats? What can be said about the anemia?

FeLV positive cats; nonregenerative

What is interesting about poodle dogs?

will have macrocytosis but are not anemic

When can erroneous macrocytosis occur?

A
P
P

• autoagglutination of erythrocytes

• prolonged blood storage before assay

• persistent hypernatremia

When is it common to see microcytosis (low MCV)?

chronic iron deficiency

When else will you see microcytosis?

P
O

• portosystemic shunts, primarily in dogs

• oriental dog breeds without anemia

When will you see spurious microcytosis in animals?

P
P

• platelets counted as erythrocytes in severely anemic patients

• persistent hyponatremia in dogs

When will you see low MCHC values?

R
C

• regenerative anemia, especially with high numbers of reticulocytes present (macrocytic)

• chronic iron deficiency anemia (microcytic)

When will you see high MCHC values (macrochromic)?

I
I
H
L
E

• intravascular hemolysis

• in vitro hemolysis

• heinz bodies within erythrocytes

• lipemia

• erythrocyte agglutination in electronic counters

coefficient of variation of erythrocyte volumes and an electronic measure of anisocytosis

red cell distribution width (RDW)

direct antiglobulin test

Coomb’s assay/test

What test is most important for erythrocyte transfusions?

major cross match

What does the major cross match test do? What might incompatibilities cause?

T
T

• tests RBC of donor against serum of recipient

• tests for RBC antibodies in the serum of the recipient

serious transfusion reactions

What test is most important for neonatal isoerythrolysis test or plasma transfusions?

minor cross match

What does the minor cross match test do? What will incompatibilities cause?

T
T

• tests serum of donor against RBCs of recipient

• tests for RBC antibodies in serum of donor

less likely to cause serious blood transfusion reactions but can cause serious hemolytic reactions after colostrum absorption or plasma transfusion

When will there be increased serum iron concentration?

H
H
I
G

• hemolytic anemia and dyserythropoiesis

• hypoplastic or aplastic anemia

• iron overload

• glucocorticoids in dogs and horses

When will there be decreased serum iron concentrations?

I
A
P
M
G
I

• iron deficiency

• anemia of inflammatory disease

• portosystemic shunts

• marked erythropoiesis with inadequate iron mobilization

• glucocorticoids in cattle and goats

• intense exercise in dogs and horses

What does serum ferritin concentration correlate with?

total body iron stores

When will there be increased serum ferritin concentration?

I
H
I
M
T

• iron overload

• hemolytic anemia

• inflammation

• malignant histicytosis

• transiently in exercising horses and dogs

When will there be decreased serum ferritin concentration?

iron deficiency

What is a commonly used methemoglobin assay?

methemoglobin spot test

What typically causes methemoglobinemia? What are specifics?

A
B
P
H
F
C
R
N
S

• acetaminophen

• benzocaine

• phenazopyridine

• hydroxyurea

• fermented bok choy

• copper toxicity in sheep and goats

• red maple toxicity in horses

• nitrite toxicity in ruminants eating nitrates

• skunk musk

recognized in many breeds of dogs and in DSH cats that is an autosomal recessive inheritance that generally has no clinical signs except cyanotic appearing skin, mucous membranes, and tongue that is often not recognized until surgery when blood appears brownish

methemoglobin reductase deficiency (cytochrome-b5 reductase deficiency)

What is the concentration of serum EPO dependent on?

production by the kidney and utilization by erythroid cells

Where will there be increased serum EPO?

M
S

• most anemias

• secondary erythrocytosis

When will there be decreased serum EPO?

C
P

• chronic renal disease

• primary erythrocytosis