Clin Lab Med Quiz #2

what percent of our weight is our blood volume (in liters)

7%

how many liters of blood does a 70 kg pt have

4.9 L

what are the two components of blood volume

RBCs and plasma

how does acute blood loss affect the components of blood volume (and hematocrit)

- low plasma

- low RBCs

the hematocrit is still considered normal

how does chronic anemia affect the components of blood volume (and hematocrit)

- low RBCs (body is unable to produce them for whatever reason (most commonly iron deficiency))

- extra plasma (body can still produce it and is compensating for low RBCs)

the hematocrit is low

how does volume-overload affect the components of blood volume (and hematocrit)

- normal amount RBCs

- too much plasma (due to lots of salt and water)

the hematocrit is low

how to write fishbone diagram for a CBC

write hemoglobin over hematocrit, WBC on the left and platelets on the right

what is hemoglobin (and what is the normal range)

molecule that carries O2 in the blood

- units are g/dL

- 14 - 17.5 g/dL for men (less for women)

what is hematocrit (and what is the normal range)

percentage of blood volume made up of RBCs

- % of RBCs/blood

- if half of our BV is RBCs and the other half is plasma, hematocrit should be around 50%

- 42 - 50% (less for women)

what is RBC count (and what is the normal range)

estimation of how many RBCs are in the body

- units are millions/uL

- 4.5 - 6 mill/uL (less for women)

relationship between hemoglobin and hematocrit

hemoglobin x 3 = hematocrit

normal WBC range

4,000-11,000 per microliter

normal range of neutrophils (PMN)

45-75%

normal range of lymphocytes

15-45%

normal range of monocytes

0-15%

normal range of eosinophils

0-5%

normal range of basophils

0-3%

normal platelet range

150,000-450,000 per microliter

how can aggregated platelets affect the RBC and platelet count

clumps of plts may be counted as RBCs

- falsely elevated RBC count

- falsely lowered platelet count

what does a neutrophil look like

numerous lobes

what does a lymphocyte look like

large round nucleus

what does a monocyte look like

kidney bean shaped nucleus

what does an eosinophil look like

pink, bi-lobed cell

what does a basophil look like

purple and granulated

two ways to count the number of cells in a CBC

- light impedance

- manually (looking at a peripheral smear under microscope--morphologic changes may be helpful in diagnosis)

proper definition of anemia

functional inability of blood to supply tissue with adequate oxygenation for proper metabolic function

real-life definition anemia

decrease in the circulating red cell mass

what is mean corpuscular volume (and what is the normal range)

average size of the circulating RBCs

- units are femtoliters

- 80 - 96 fL

what is red cell volume distribution width

how big is the range in RBC sizes (are they all around the same size or are some big and some small)

- even if MCV is normal, the sizes could be off

- 11.5 - 14.5

microcytosis

cells are small

- MCV <80 fL

macrocytosis

cells are large

- MCV >100 fL

anisocytosis

variation in RBC size

- RDW >14.5

anisochromia

variation in color of RBCs

poikilocytosis

abnormal cell shapes

- examples: spherocytes, acanthocytes

schistocytes

fragments of RBCs

what does a peripheral blood smear look like for a pt with iron deficiency

- microcytic (they should be similar size to nucleus of lymphocyte)

- hypochromic (little pigmentation- white area within RBC is more than 1/3 of size of cell)

- poikilocytosis (some cells may have weird pencil shape)

megaloblastic vs microcytic

- microcytic- large RBCs

- megaloblastic- large AND too many lobes in nucleus

causes of megaloblastic anemia

b12 or foalte deficiency

what are reticulocytes

immature RBCs

what does the reticulocyte count tell us

can the bone marrow produce new RBCs in response to anemia?

what does it mean if the reticulocyte count is low

bone marrow does not have the materials or ability to make more RBCs

- iron, vitB12, or folate deficiency

- anemia of inflammation (can't put RBCs together)

what does it mean if the reticulocyte count is high

bone marrow CAN make RBCs and its not a supply or ability issue

- high bc BM is trying to compensate for RBC loss

- hemolytic anemia

- anemia d/t acute blood loss

what does it mean if reticulocytes have ribosomal RNA in them

they are VERY immature

- body is trying SO hard to increase RBC count and is releasing blood cells well before they are ready

what labs should you order if you suspect missing substrate as cause of anemia

- iron studies

- vit B12 levels

- folate levels (serum and RBC folate levels)

(suspected with low retic count)

what labs should you order if you suspect hemolysis as cause of anemia

- bilirubin (would go up)

- lactate dehydrogenase (would go up)

- haptoglobin (would go down)

- direct antiglobulin test

- UA

what labs should you order if you suspect abnormal hemoglobin production as cause of anemia

- hemoglobin electrophoresis

functional approach to anemia diagnosis

think about WHY someone became anemic

- blood loss (acute or chronic)

- impaired production

- increased destruction (hereditary or inherited)

morphologic approach to anemia diagnosis

- determine MCV (are cells small, normal, or large)

what are the microcytic anemias

- iron deficiency

- thalassemias

- anemia of inflammation (chronic disease)

- heavy metal poisoning

- hereditary sideroblastic

what are the normocytic anemias

- acute blood loss

- EARLY iron deficiency anemia

- anemia of inflammation (chronic disease)

- renal insufficiency

what are the macrocytic anemias

- folate deficiency

- ethanol abuse

- vitB12 deficiency

- AML

- reticulocytosis

CBC abnormalities consistent with iron deficiency

- decreased RBCs, Hgb, and HCT

- microcytic (low MCV)

- increased RDW (anisocytosis)

- hypochomia

- poikilocytosis

iron studies (and when would you get each one)

- serum Fe/total iron binding capacity ratio (percent that transferrin is saturated with Fe)

- ferritin (under normal circumstances, ferritin is a DIRECT reflection of body iron stores; ferritin rises during inflammation)

ferritin is best, but you can't get it if pt is sick

normal serum Fe/total iron binding capacity ratio

25-40%

how do the labs change as patient develops Fe deficiency

- ferritin begins to decrease early

- anisocytosis (high RDW)- more small cells than large

- MCV and MHC decrease

- hypochromia, low Hgb, tranferrin sat <16%

why is a retic count so important

- if high, it implies there is hemolysis or blood loss- these are URGENT kinds of anemia

- if retic count is low or inappropriately normal, lab workup is done based on MCV

if the patient has macrocytic anemia and you suspect folate deficiency, what tests do you do

- START with serum folate (cheap and easy, but can easily be affected by outside factors [eating])

- if normal or high, do RBC folate level

tests for vitB12 deficiency (due to malabsorption)

Schilling test

- radiolabeled vitB12 ingested

- check urine (if low, it suggests malabsorption of B12)

- to figure out WHY give: intrinsic factor (pernicious anemia), abx (bacterial overgrowth), pancreatic enzymes (pancreatic dysfunction)

what do you do if CBC shows normocytic anemia

- check all iron studies to rule out early Fe deficiency

- differentiate anemia of chronic disease from Fe deficiency

how does anemia of chronic disease affect iron

- iron storage in organs increases and iron gets trapped in macrophages (serum Fe is LOW)

- ferritin increases

- transferrin is normal/low (body still detects iron so it doesn't increase transferrin)

lab values for Fe deficiency vs chronic disease

- transferrin: increased in Fe, decreased in chronic D

- % saturation: decreased in Fe D, normal in chronic D

- ferritin: decreased in Fe D, increased in chronic D

how do chronic diseases cause anemia

- trapped iron --> less utilization

- decreased EPO (kidney disease)

- inflammatory disease --> cytokines decrease iron utilization

etiologies of anemia of chronic disease

- infections (HIV, chronic viral infections, fungal, bacterial)

- connective tissue disorders

- systemic malignancy

- renal failure

- liver disease

- alcoholism

- endocrine disorders

hallmark of anemia of chronic disease

high ferritin

what does it mean if retic count is high but there is no sign of acute blood loss

hemolysis is likely

- drug and family history

- check haptoglobin, LDH, bilirubin, and Coombs test

- do hemoglobin electrophoresis if indicated

what is haptoglobin

- protein that binds to free hemoglobin from RBC breakdown (or hemolysis)

- delivers hemoglobin to liver to convert it to bilirubin

- if low- think LOTS of free hemoglobin --> hemolysis

what is considered very low haptoglobin

< 7 mg/dL

what happens if there is too much free hemoglobin and not enough haptoglobin

- free hemoglobin in plasma

- gets filtered by kidneys --> urine or some is reabsorbed

increased serum LDH and decreased haptoglobin is a sign of

hemolysis

how is bilirubin affected in hemolysis

- breakdown of RBCs causes release of unconjugated bilirubin

- indirect/unconjugated bilirubin is elevated

how do you measure indirect bilirubin

order total bilirubin and direct bilirubin

- then calculate indirect

which form of bilirubin is water-soluble (and may be excreted in urine if liver becomes damaged and it back-leaks)

conjugated/direct bilirubin

why is it that if the liver is damaged, the main sign is conjugated hyperbilirubinemia

when liver becomes damaged, all steps of bilirubin conjugation are affected (uptake of bili by hepatocytes, conjugation, and excretion into bile) but excretion is affected the MOST and the EARLIEST

- later on in the disease course, it will be a mixed hyperbilirubinemia

etiologies of unconjugated hyperbilirubinemia

overproduction of bilirubin in blood d/t hemolysis

- hemolytic drugs

- autoimmune rxn

- sickle cell

- infections like malaria and babesiosis

can unconjugated bilirubinemia cause urine darkening

no

what is the direct Coombs test

direct antiglobulin test

- used to see if RBCs have antibodies already bound to them (and causing hemolysis)

- examples: autoimmune (body made antibodies binding to own RBCs), drug-induced (drug made body make antibodies binding to own RBCs)

how to do direct Coombs test

- take sample of blood from pt

- remove pts serum (we want JUST the RBCs)

- combine RBCs with Coombs reagent (anti-human globulin)

- if RBCs are coated with antibodies, reagent will bind to antibodies and cause RBCs to clump

intravascular vs extravascular hemolysis (what is it, what are examples, and how to tell difference)

- intravascular: occurs in circulation, releasing Hgb into plasma; causes: trauma, DIC, toxic damage; produces schistocytes

- extravascular: RBCs are phagocytized by macrophages in spleen and liver; causes: RBC membrane or structure abnormalities; produces spherocytes

what to do if intravascular hemolysis is suspected

- measure plasma Hb concentration (looking for hemoglobinemia)

- measure free Hb in urine (looking for hemoglobinuria)

what happens if a patient has anemia with pancytopenia

this means ALL cell lines are affected (RBCs, WBCs, platelets)

- this is a bone marrow issue!- aplastic anemia