Cross Species - Red Blood Cell Parameters

Question 1

what are the 3 cell types evaluated on a CBC? what does it provide information on?

Answer 1

erythrocytes, leukocytes, & platelets - info on production, structure, & function

Question 2

what is hematopoiesis?

Answer 2

blood cell production that occurs primarily in the bone marrow

Question 3

what does the bone marrow contain which produce cells? what are the precursors?

Answer 3

progenitor/stem cells & mesenchymal stromal cells that secrete cytokines to control stem cell differentiation - myeloid precursors for WBC, erythroid precursors for RBC, & megakaryocytes for platelets

Question 4

why is it important that hematopoietic stem cells are multipotent?

Answer 4

they can self-renew & can differentiate into all cell types

Question 5

what causes red blood cell production?

Answer 5

erythropoietin is released from the kidneys in response to tissue hypoxia

Question 6

what is seen on a CBC in an animal with a lack of erythropoietin?

Answer 6

non-regenerative anemia

Question 7

what is the exception to circulating nucleated red blood cells?

Answer 7

snakes, fish, amphibians, & birds all have circulating nucleated red blood cells

Question 8

how do you differentiate between immature & mature RBC?

Answer 8

immature red blood cells, rubricytes, have a nucleus while mature RBC don’t

Question 9

what is the last red blood cell stage prior to a mature RBC? what do they look like?

Answer 9

reticulocytes - no nucleus, but they contain RNA that can be seen with a special stain

Question 10

what is the purpose of counting reticulocytes on a CBC?

Answer 10

to assess the bone marrow response to anemia

Question 11

T/F: you can count reticulocytes from a horse CBC to assess their anemia

Answer 11

false - reticulocytes are not present in horses!!!

Question 12

T/F: red blood cells are very susceptible to oxidative damage

Answer 12

TRUE

Question 13

what are heinz bodies?

Answer 13

RBC containing oxidized precipitated hemoglobin

Question 14

what are the big causes of oxidative damage to RBC?

Answer 14

toxins - acetaminophen in cats, red maple leaf toxicity in horses, & alium species in onions & disease - feline hepatic lipidosis, systemic inflammation, & neoplasia

Question 15

what is the lifespan of RBC in cats?

Answer 15

2 months

Question 16

what is the lifespan of RBC in dogs?

Answer 16

3 months

Question 17

what is the lifespan of RBC in cows & horses?

Answer 17

about 5 months

Question 18

how are RBC removed from circulation?

Answer 18

splenic macrophages remove them, iron is recycled & used again in bone marrow - poryphrin produced by heme breakdown is excreted via a bilirubin pathway

Question 19

what does it mean if hemoglobinemia is seen in circulation?

Answer 19

indicates RBC rupture is occuring within the vasculature - intravascular hemolysis, clinically correlates with babesiosis

Question 20

what does extravascular hemolysis cause?

Answer 20

bilirubinemia (pre-hepatic icterus) from increased production of bilirubin precursos (canine IMHA & equine infectious anemia)

Question 21

T/F: hematocrit & PCV are not the same

Answer 21

TRUE

Question 22

how is HCT calculated?

Answer 22

HCT = (MCV x RBC)/10

Question 23

how is PCV measured?

Answer 23

directly measured from centrifuged microhematocrit tube & then interpreted in conjunction with total solids

Question 24

how are total solids measured?

Answer 24

measurement of plasma protein using a refractometer

Question 25

what is the buffy coat?

Answer 25

layer of WBC & platelets on top of the RBC

Question 26

what does a spurious increase in HCT/PCV indicate?

Answer 26

insufficient centrifugation or cell swelling with storage for HCT

Question 27

what are the main causes of a pathologic increase in HCT & PCV?

Answer 27

dehydration is most common, splenic contraction, epinephrine release in horses, & polycythemia

Question 28

what is polycythemia?

Answer 28

primary myeloproliferative disease such as polycythemia vera or secondary polycythemia due to increased erythropoetin production (congenital heart disease causing left to right shunting)

Question 29

what does a spurious decrease in HCT or PCV indicate?

Answer 29

in vitro hemolysis or underfilled EDTA tube causing sample dilution

Question 30

what are the 3 mechanisms of true anemia?

Answer 30

RBC breakdown, RBC loss, & lack of production

Question 31

what is an example of a disease causing break down of RBC resulting in anemia?

Answer 31

IMHA in dogs

Question 32

what is an example of a disease causing blood loss of RBC resulting in anemia?

Answer 32

external - trauma, guttural pouch mycosis & internal/occult - gi losses, renal losses, & body cavity bleed

Question 33

what is an example of a disease causing decreased production of RBC resulting in anemia?

Answer 33

neoplasia & toxin-mediated bone marrow suppression

Question 34

what is an example of an iatrogenic cause of anemia?

Answer 34

over hydration

Question 35

what parameters are related to hemoglobin on a CBC?

Answer 35

mean cell hemoglobin (MCH) & mean cell HGB concentration (MCHC)

Question 36

hemoblobin can be estimated based off of HCT how?

Answer 36

1/3 of hematocrit

Question 37

what are some causes of a spurious increases in hematocrit?

Answer 37

lipemia, heinz bodies, & high numbers of nRBC

Question 38

how is MCH calculated?

Answer 38

HGB/RBC - detects the average amount of HGB in cells, but rarely used because it is affected by cell size, so the result is difficult to interpret

Question 39

how is MCHC calculated? what does it represent?

Answer 39

(HGB/HCT) X 100 - average RBC hemoglobin concentration, calculation accounts for cell size because HCT = RBC X MCV

Question 40

T/F: an increase in MCHC is ALWAYS spurious

Answer 40

TRUE

Question 41

why are increases in MCHC always spurious? what are some examples of causes?

Answer 41

RBC cannot contain increased hemoglobin!!!! causes include lipemia, hemolysis, many rRBC, & agglutination

Question 42

what are causes of decreased MCHC?

Answer 42

regenerative anemia & iron deficiency anemia - immature RBC contain less hemoglobin!!!

Question 43

what are some spurious causes of increased MCV?

Answer 43

agglutination & excessive blood storage time

Question 44

what does an increase in MCV mean?

Answer 44

macrocytosis is present

Question 45

how is MCV calculated? what does it represent?

Answer 45

(PCV/RBC) X 10 - measure of RBC volume

Question 46

what are some pathologic causes of an increased MCV?

Answer 46

regenerative anemia, RBC swelling due to membrane abnormalities, folate deficiency, B12 deficiency, & myelodysplasia (cats with FeLV)

Question 47

what breed is associated with a physiologic cause of a decreased MCV?

Answer 47

akita

Question 48

what is an example of a physiologic cause of a decreased MCV?

Answer 48

young animals - puppies & kittens less than 16 weeks old & calves & foals less than 2 months old

Question 49

what is an example of a pathologic cause of a decreased MCV?

Answer 49

iron deficiency - chronic external blood loss (gi bleeding) or insufficient intake (piglets)

Question 50

what is RDW?

Answer 50

measures the variation in RBC volume (anisocytosis)

Question 51

what does an increase in RDW indicate?

Answer 51

more variation in RBC size/volume - seen with anemia due to larger immature RBC if regenerative or smaller/older RBC if non-regenerative

Question 52

what special stain is required for a reticulocyte count?

Answer 52

methylene blue

Question 53

how long does a regenerative anemia take to see on a CBC?

Answer 53

3-5 days

Question 54

what does a higher count of reticulocytes indicate?

Answer 54

there is a regenerative anemia

Question 55

T/F: it is difficult to assess if an anemia is regenerative or non-regenerative in a horse without a bone marrow aspirate

Answer 55

TRUE

Question 56

when do you need to manually count WBC when considering nRBC?

Answer 56

if greater than 5/100 WBC - analyzers count the nRBC as WBC!!

Question 57

when may you see an increase in nRBC?

Answer 57

regenerative anemia, bone marrow injury, dogs with heat stroke, lead poisoning, & splenic hemangiosarcoma

Question 58

why do you need to do a microscopic slide for RBC?

Answer 58

analyzers won't tell you anything on changes in RBC morphology