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Heme/Onc > Complete Blood Count and Red Cell Morphology > Flashcards

Complete Blood Count and Red Cell Morphology Flashcards

1. Understand the definition of each red cell parameter (such as MCV, MCH and MCHC) and “rule of three” (MKS 1a) 2. Identify the most common interferences that may cause false CBC results (MKS 3c) 3. Recognize variations in red cell morphology and the associated underlying clinical conditions (MKS 1b)

1
Q

What are the components of blood?

A
  • Blood is a fluid connective tissue constituting ~7% of total human body weight (~5 liters)
  • The peripheral blood allows us a “window” into the functional and biologic status of a patient
  • It is easily accessible via a “blood draw” and the composition of the cells and plasma contents gives the physician the ability to quickly assess the health status of the patient
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2
Q

What are the components of the CBC and the differential report?

A
  • CBC: Measurement of total WBC count and specific RBC parameters by automated hematology analyzers
    • The principles of measurement vary depending on the instrument
  • Differential: The percentage (%) of each subtype of WBC over total WBC count; the absolute count of each subtype of WBC per microliter (UL)
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3
Q

What are the parameters evaluated for complete RBC counts? What accounts for falsely high and low RBC counts?

A
  • RBC count (M/UL):
    • Direct counting of the number of “particles” within certain size ranges in a whole blood sample by an automated instrument
    • RBC and WBC are counted together (the 500 times excess of RBCs over WBCs makes the error caused by inclusion of WBCs in RBC count insignificant)
    • Interference
      • Falsely high RBC count: Marked leukocytosis (>100 K/UL); giant platelets
      • Falsely low RBC count: RBC aggregation (cold agglutinin); microcytosis; fragmented RBC
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4
Q

What are the ways of measuring hemoglobin and what are some causes of interference?

A
  • Direct measurement of HGB concentration in RBC-lysed blood sample by spectrophotometer (light absorbance) in automated instrument
    • Light absorbed is directly proportional to the concentration of HGB.
  • Interference
    • Falsely high HGB: increased sample turbidity
      • hyperlipidemia
      • hyperbilirubinemia
      • abnormal protein
      • marked leukocytosis)
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5
Q

What is the RBC count? How is it measured? And what are some sources of interference?

A
  • Indirect measurement (calculated) by automated instrument of percent of blood volume occupied by RBCs:
    • **HCT=RBC volume/Total blood volume x100 **
  • Interference
    • Falsely high HCT: marked leukocytosis; hyperglycemia
    • Falsely low HCT: red cell agglutination; microcytosis
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6
Q

What is the rule of three’s when it comes to RBC count?

A
  • “Rule of three”
    • Example: RBC count 4.6; HGB 14.4; HCT 42.4
    • RBC count x 3 = HGB
    • HGB x 3 = HCT
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7
Q

What is MCV? What are the normal values? And what are some of the interferences that can alter results?

A
  • Mean Corpuscular Volume (fL)
  • Measurement and calculation of average red cell volume (femtoliter: 1.0-15 liter) by automated instrument
    • Low MCV-microcytosis (e.g. iron deficiency anemia)
    • High MCV-macrocytosis (e.g. macrocytic anemia due to B12 deficiency)
  • Interference
    • Falsely high MCV: red cell agglutination
    • Osmotic abnormalities (hyperglycemia, hypernatremia)
    • Signiticantly increased young RBC (larger than old RBC)
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8
Q

What is MHC and MCHC? How is evaluated and calculated?

A
  • MCH (Mean corpuscular hemoglobin) & MCHC (Mean corpuscular hemoglobin concentration)
    • MCH: Indirect measurement (calculated from other parameters) of the mean hemoglobin content (pg: pictogram; 1pg=1.0-12 g) in RBC cell (how much hemoglobin in a red blood cell)
      • MCH=HGB (g/L)/RBC count (/L)
    • MCHC: Indirect measurement (calculated from other parameters) of hemoglobin concentration (%) in RBC cells (what is the concentration of HGB in red blood cells)
      • MCHC=HGB (g/dL)/HCT x 100
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9
Q

What is RDW? What are the parameters of this measurement? And what is “anisocytosis”?

A
  • RDW (coefficient variation of the red cell distribution width (RDW-CV); %)
    • Indication of variation of red cell volume/size (higher RDW correlates with higher degree of volume/size variation in RBC)
  • Morphologically, RBC variation in size called “anisocytosis”; variation in shapes called “poikilocytosis” and variation in both called “anisopoikilocytosis” such as in iron deficiency anemia
  • “Width” refers to RBC size-distribution width in histogram, not the width of RBC itself.
    • RDW-CV: Red cell distribution width-coefficient variation (RDW used in CBC report)
    • RDW-SD: Red cell distribution width-standard deviation
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10
Q

How is platelet count evaluated? What are some caues of interference in this measurement?

A
  • Direct counting of the number of “particles” within certain size ranges in a whole blood sample by an automated instrument
  • Interference
    • Falsely low platelet count: clotted sample (platelets trapped in the blood clots)
    • Platelet clumping (cannot be counted as individual platelet)
    • Frequent giant platelets (giant platelets may be counted as WBC or RBC because of their large size)
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11
Q

What are the featuers of normal red blood cell morphology? What can go wrong with the morphology?

A
  • Normal red blood cell
    • A normal red blood cell is an anucleated, biconcave disk-shaped cell measuring about 7-8 mm in diameter
    • The life span of a normal circulating red blood cell is about 120 days
  • Reticulocytes are young RBCs consisting 1-2% of red cells in the peripheral blood
    • Increased number of reticulocytes indicates increased bone marrow production of red cells in response to anemia or blood loss
    • Lack of appropriate reticulocyte response in an anemic patient suggests defect in the bone marrow production of red cells (such as acute leukemia, myelodysplastic syndrome, metastatic carcinoma)
  • The bulk of the cytoplasmic component of RBC is hemoglobin which consists 90-95% of dry weight
    • The major role of hemoglobin is oxygen and CO2 transport
    • The red blood cells also contain enzymes that participate in glycolytic and hexose monophosphate pathways
  • The red blood cells can vary in size (ansiocytosis) and shape (poikilocytosis). Some of the morphologic changes are associated with certain clinical conditions. Thus, review of the peripheral blood smear may provide important information for assessment of the patient’s underlying health problems.
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12
Q

What does RBC agglutination look like? What conditions are associated?

A
  • RBCs form clumps
  • Conditions
    • cold agglutinins
    • some lymphomas with monoclonal IgM
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13
Q

What is Roleaux formation? What conditions are associated?

A
  • “stacks of coins” formation
  • Conditions:
    • Multiple myeloma (plasma cell malignancy)
    • Some lymphomas
    • Chronic inflammation and infection
    • Chronic liver diseases
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14
Q

What are hypochromic RBCs? What conditions are associated?

A
  • Central pallor >1/3 of the RBC (pale red cell)
  • Conditions:
    • iron deficiency anemia
    • thalassemia
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15
Q

What are ovalocyte (elliptocyte) cells? What conditions are associated?

A
  • Oval red cells
  • Conditions:
    • hereditary elliptocytosis
    • B12/folate deficiency
    • iron deficiency; others
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16
Q

What are target cells? What conditions are they associated with?

A
  • Targetoid shape, central darkening
  • Conditions:
    • liver disease
      • lipid disorder
      • hemoglobinopathy (e.g. thalassemia, hemoglobin C)
17
Q

What are Burr cells? What conditions are associated?

A
  • Symmetric short, sharp projections
  • Conditions:
    • kidney disease (acute renal failure)
    • iron deficiency
18
Q

What are acanthocytes? What conditions are associated?

A
  • Asymmetric, unequal long projections
  • Conditions:
    • chronic liver disease
    • lipid disorder
    • abetalipoproteinemia
19
Q

What is a teardrop cell? What conditions are associated?

A
  • Teardrop cell
  • Conditions:
    • myelofibrosis
    • bone marrow infiltrate (e.g. carcinoma)
    • iron deficiency
20
Q

What are spherocytes cells? What conditions are associated?

A
  • Dark RBC with no central pallor
  • Conditions:
    • hereditary spherocytosis
    • immune-mediated hemolytic anemia
21
Q

What are Bite cells? What are the associated conditions?

A
  • One or more “bites” in RBC
  • Conditions:
    • ​Heinz body hemolysis
      • G-6PD deficiency
      • unstable hemoglobins
      • oxidant drugs
22
Q

What is a schistocyte? What conditions are related to this finding?

A
  • Irreglarity shaped RBC fragments
  • Conditions:
    • microangiopathic hemolytic anemia
    • such as DIC (disseminated intravascular coagulation)
    • HUS (hemolytic uremic syndrome)
    • TTP (thrombotic thrombocytopenic purpura)
    • Artificial cardiac valves
23
Q

What does sickle cell look like?

A
  • Curved RBC with sharp ends
  • Conditions - sickle cell disease (Hb S/S)

Heme/Onc (50 decks)

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