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AMT MLS Exam - Hematology > Hematology - Hemoglobin, Hemoglobinopathies, & Thalassemia > Flashcards

Hematology - Hemoglobin, Hemoglobinopathies, & Thalassemia Flashcards

1
Q

What is the function of hemoglobin?

A

transport oxygen

-it is an oxygen-transporting protein within RBCs

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2
Q

Describe the hemoglobin molecule.

A

-made of 4 polypeptide chains (globin) and 4 heme groups, each containing a protoporphyrin ring with ferrous (Fe2+)iron

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3
Q

Where is hemoglobin produced?

A

-in the cytoplasm of the developing normoblasts in the bone marrow, primarily the polychromatophilic normoblast

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4
Q

What is the reference method for determining hemoglobin concentration?

A

cyanmethemoglobin method - measures all type of hemoglobin EXCEPT sulfhemoglobin

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5
Q

65% of hemoglobin synthesis occurs in ___________.

A

immature nRBCs

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6
Q

35% of hemoglobin synthesis occurs in __________.

A

reticulocytes

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7
Q

Where does globin synthesis occur?

A

ribosomes

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8
Q

Describe intravascular hemolysis.

A

occurs when hemoglobin breaks down in the blood and free hemoglobin is released into the plasma

-the free hemoglobin binds to haptoglobin and is phagocytized in the liver by macrophages

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9
Q

Describe extravascular hemolysis.

A

occurs when senescent/old RBCs are phagocytized by macrophages in the liver/spleen

-the protoporphyrin ring is metabolized to bilirubin and urobilinogen; excreted in urine/feces
-globin chains are recycled into the amino acid pool for protein synthesis
-iron binds to transferrin and is transported to the bone marrow for new RBC production OR stored as ferritin/hemosiderin

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10
Q

What type of iron can bind to oxygen?

A

ferrous (Fe2+)

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11
Q

What type of iron binds to transferrin?

A

ferric (Fe3+)

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12
Q

What type of iron is measured by serum iron?

A

ferric (Fe3+) bound to transferrin

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13
Q

What does TIBC measure?

A

the total amount of iron that transferrin can bind when fully saturated

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14
Q

What does serum ferritin measure?

A

indirectly measures the storage iron in tissues and bone marrow

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15
Q

What is the Fe transport protein called?

A

transferrin

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16
Q

What must be present for heme synthesis?

A

iron and protoporphyrin

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17
Q

What is the major Fe storage form?

A

ferritin

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18
Q

What is the water insoluble Fe storage form (long term)?

A

hemosiderin

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19
Q

What happens to excess iron?

A

stored in tissues and organs -> can lead to hemosiderosis, hemochromatosis (organ damage)

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20
Q

What are the protoporphyrin synthesis precursors?

A

early precursors: delta aminolevulinic acid, porphobilinogen

later precursors: uroporphyrinogen, coproporphyrinogen, protoporphyrin

REMEMBER: While in the DELTA, POUR YOUR COP, PRONTO, a cup of HEME.

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21
Q

Describe the molecular structure of hemoglobin A.

A

2 alpha chains
2 beta chains

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22
Q

What is the adult reference value for hemoglobin A?

A

> 95%

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23
Q

What is the newborn reference value for hemoglobin A?

A

20%

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24
Q

Describe the molecular structure of hemoglobin A2.

A

2 alpha chains
2 delta chains

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25
Q

What is the adult reference value for hemoglobin A2?

A

1.5-3.7%

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26
Q

What is the newborn reference value for hemoglobin A2?

A

<1%

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27
Q

Describe the molecular structure of hemoglobin F.

A

2 alpha chains
2 gamma chains

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28
Q

What is the adult reference value for hemoglobin F?

A

<2%

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29
Q

What is the newborn reference value for hemoglobin F?

A

50-85%

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30
Q

Describe the molecular structure of hemoglobin S.

A

valine substituted for glutamic acid in the 6th position of the beta chain

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31
Q

What is the reference range for hemoglobin S in the adult and newborn?

A

0

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32
Q

Describe the molecular structure of hemoglobin C.

A

lysine substituted for glutamic acid in the 6th position of the beta chain

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33
Q

What causes methemoglobin?

A

iron oxidized to ferric (Fe3+) state

-usually acquired from exposure to oxidants
-rarely inherited

34
Q

What effect does methemoglobin have?

A

-it cannot bind oxygen (since iron is in ferric state)
-cyanosis, possibly death

35
Q

What is the reference range for methemoglobin?

A

</=1%

36
Q

What RBC inclusions are seen on the peripheral smear when methemoglobin is present?

A

Heinz bodies

37
Q

How is methemoglobin treated?

A

with methylene blue

38
Q

What causes sulfhemoglobin?

A

sulfur bound to heme

-acquired from exposure to drugs/chemicals

39
Q

What effect does sulfhemoglobin have?

A

oxygen affinity is 1/100th normal

-cyanosis

40
Q

What is the reference range for sulfhemoglobin?

A

0

41
Q

Can sulfhemoglobin be converted back to hemoglobin?

A

NO

42
Q

Is sulfhemoglobin detected in the cyanmethemoglobin method?

A

NO

43
Q

What causes carboxyhemoglobin?

A

carbon monoxide bound to heme

44
Q

What is the effect of carboxyhemoglobin?

A

decreased oxygen to tissues

-can be fatal

45
Q

What is the reference range for carboxyhemoglobin?

A

<1%

46
Q

Why does the skin turn cherry red for carboxyhemoglobin?

A

affinity of hemoglobin for carbon monoxide is 200x greater than for oxygen

47
Q

What is deoxyhemoglobin?

A

hemoglobin with ferrous iron but no oxygen

-seen in venous circulation

48
Q

What forms of hemoglobin are normally found in circulation?

A

-primarily oxyhemoglobin and deoxyhemoglobin
-to a lesser extent, carboxyhemoglobin and methemoglobin

-sulfhemoglobin is NOT normal

49
Q

What is the normal value for hemoglobin in an adult male?

A

14-18 g/dL

(140-180 g/L)

50
Q

What is the normal hemoglobin value for an adult female?

A

12-15 g/dL

(120-150 g/L)

51
Q

What is the normal hemoglobin value for a newborn?

A

16.5-21.5 g/dL

(165-215 g/L)

52
Q

What are the normal hemoglobins?

A

A, A2, and F

53
Q

What globin chains are found in Hb A?

A

2 alpha and 2 beta

54
Q

What globin chains are found in Hb A2?

A

2 alpha and 2 delta

55
Q

What globin chains are found in Hb F?

A

2 alpha and 2 gamma

56
Q

What are the 2 broad categories of hemoglobin disorders?

A
  1. Qualitative - structurally abnormal hemoglobin such as Hb S or Hb C is produced
  2. Quantitative - (thalassemias) normal hemoglobins are produced in abnormal concentrations
57
Q

What is oxygen affinity?

A

the ability of hemoglobin to bind or release oxygen

58
Q

Oxygen Dissociation Curve - right shift

A

-decreases oxygen affinity, more oxygen released to tissues

-HIGH 2,3-bisphosphoglycerate level
-INCREASED body temperature
-DECREASED body pH

59
Q

Oxygen Dissociation Curve - left shift

A

-increases oxygen affinity, less oxygen released to tissues

-LOW 2,3-bisphosphoglycerate level
-DECREASED body temperature
-INCREASED body pH

60
Q

Describe the migration of hemoglobins on cellulose acetate at pH 8.6.

A

Cathode (-) to Anode (+):
(slowest to fastest)
1. C, A2, E, O(arab), C(Harlem)
2. S, D, G, L
3. F
4. A

“Crawl” => “Slow” => “Fast” => “Accelerated”

61
Q

What controls are required for hemoglobin electrophoresis?

A

at least Hgb A, F, and S

62
Q

Describe the migration of hemoglobins on citrate agar at pH 6.2.

A

application point in middle of cathode (-) and anode (+): (left to right)

  1. F
  2. A, A2
  3. S
  4. C

“Florida (citrus) Association of (application point) Smelly Cats.”

63
Q

Why is citrate agar at acid pH used when abnormal hemoglobins are identified on cellulose acetate at pH 8.6?

A

it separates hemoglobins that migrate together on cellulose acetate

64
Q

What is the most common thalassemia in the U.S.?

A

heterogenous beta thalassemia (beta thalassemia minor)

-usually benign

65
Q

What are lab findings in beta thalassemia minor?

A

-mild anemia
-increased RBCs
-mild to moderate microcytosis and hypochromia
-normal RDW

HALLMARK of this disorder = elevated Hb A2 (3.5-8%)

66
Q

Which hemoglobin is resistant to alkali denaturation and acid elution?

A

Hemoglobin F

-Kleihauer-Betke stain can be used to demonstrate Hb F; cells containing Hb F resist acid elution and stain pink; cells containing Hb A lose hemoglobin and appear as “ghost cells”

67
Q

How does the fetus benefit from a high concentration of hemoglobin F?

A

Hb F has increased oxygen affinity so the fetus is able to extract oxygen from the maternal blood supply

68
Q

Describe the hemoglobin electrophoresis pattern and RBC morphology typically seen with sickle cell anemia (SS).

A

> 80% Hb S
1-20% Hb F
normal A2
no A

Blood smear:
-sickle cells
-anisocytosis
-target cells
-nRBCs
-spherocytes
-Howell Jolly bodies
-basophilic stippling
-Pappenheimer bodies
-polychromasia
-RBCs = normocytic, normochromic

69
Q

Describe the hemoglobin electrophoresis pattern and RBC morphology typically seen with sickle cell trait (AS).

A

50-65% Hb A
35-45% Hb S
normal Hb F (<2%)
normal to slightly increased A2

Blood smear:
-normal except for a few target cells
-sickle cells not seen except under extreme hypoxic conditions

70
Q

What causes sickle cells to sickle?

A

when deoxygenated, Hb S polymerizes and the resulting intracellular crystals deform the RBC

71
Q

A solubility test for sickling hemoglobins is performed and the black lines cannot be seen through the tube due to turbidity. What should be done next?

A

cellulose acetate electrophoresis

-the solubility test is a screening test and is not specific for Hb S
-the solubility test does not differentiate SS from AS

72
Q

How is sickle cell anemia differentiated from sickle cell trait?

A

hemoglobin electrophoresis

73
Q

What additional testing is required when a hemoglobin migrating to the “S” position is observed on cellulose acetate hemoglobin electrophoresis?

A

because other hemoglobins (Hb D and Hb G) migrate to the same area, a solubility test or other acceptable confirmatory test must be performed before the hemoglobin is reported as hemoglobin S.

74
Q

Why can screening tests not detect sickle cell anemia in newborns?

A

the predominant hemoglobin in newborns is Hb F

-the amount of Hb S in newborns with sickle cell anemia is below the sensitivity of the screening tests

75
Q

Describe the electrophoretic pattern and RBC morphology typically seen with hemoglobin C disease (CC).

A

> 90% Hb C
<7% Hb F
no Hb A

Blood smear:
-numerous target cells
-few spherocytes
-Hb C crystals
-normocytic, normochromic RBCs

76
Q

Describe the electrophoretic pattern and RBC morphology typically seen with hemoglobin C trait (AC).

A

60-70% Hb A
30-40% Hb C

Blood smear:
-many target cells
-slightly hypochromic RBCs

77
Q

Describe the electrophoretic pattern and RBC morphology typically seen with sickle cell disease (SC).

A

> Hb S than Hb C
normal to 7% Hb F
no Hb A

Blood smear:
-target cells
-pocketbook cells
-occasional spherocytes
-Hb SC crystals

78
Q

Describe the electrophoretic pattern and RBC morphology typically seen with beta thalassemia major.

A

little or NO Hb A
95-98% Hb F
2-5% Hb A2

Blood smear:
-target cells
-nRBCs
-basophilic stippling
-anisocytosis
-poikilocytosis

79
Q

Describe the electrophoretic pattern and RBC morphology typically seen with beta thalassemia minor.

A

> 90-95% Hb A
3.5-7% Hb A2
2-5% Hb F

Blood smear:
-hypochromic microcytic RBCs
-poikilocytosis
-target cells
-basophilic stippling

80
Q

Name a method other than electrophoresis that is used to quantitate Hb A2.

A

chromatography - either anion exchange column chromatography or HPLC

AMT MLS Exam - Hematology (6 decks)

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