Lecture 3 Erythrocytes and The Erythrogram

Erythrocytes

red blood cells

Erythrocytes can be measured based on ____ & ____ measures

quantitative & qualitative

Quantitative measures to evaluate erythrocytes (red blood cells)

• Measured or calculated(formulas)

• Parameters related to red cell mass

  • RBC count

  • Hgb concentration

  • HCT (Hematocrit)

  • PCV

• Red cell indices (are laboratory values reported as part of a complete blood count (CBC) that describe the size, hemoglobin content, and hemoglobin concentration of red blood cells (RBCs))

  • MCV (mean cell volume)

  • MCH (mean corpuscular hemoglobin)

  • MCHC (mean corpuscular hemoglobin concentration)

  • RDW (red cell distribution width)

What are the 4 red cell indices? What do RBC indices help do?

• MCV (mean cell volume)

• MCH (mean corpuscular hemoglobin)

• MCHC (mean corpuscular hemoglobin concentration)

• RDW (red cell distribution width)

• Red cell indices are laboratory values reported as part of a complete blood count (CBC) that describe the size, hemoglobin content, and hemoglobin concentration of red blood cells (RBCs).

Qualitative measures to evaluate erythrocytes (red blood cells)

▪ Poikilocytosis– Alteration in cell shape (Think: “Pokey Shapes”)
▪ Chromasia– Alteration in cell color (“c”/chroma for color”)
▪ Anisocytosis– Alteration in cell size (Think: “Any size”)
▪ Agglutination– Clumping of RBCs (Think: “Glue = Clump”)
▪ Presence/Absence of hemoparasites

• Rouleaux— Stacking of RBCs in linear chains, resembling a stack of coins. (think: “roll” as in roll of coins)

Which parameters are directly measured?

• PCV

• Hgb concentration

• RBC count

Mnemonics to Remember the “Directly Measured Trio”

1. “Pretty Hot Red”

• P = PCV

• H = Hemoglobin

• R = RBC count

2. Think: These are the basic ingredients

• You first need the volume (PCV), the pigment (Hb), and the number (RBC count) before you can calculate anything else.

3. Visual trick: Imagine drawing blood → you see (measure directly):

• How much of the tube fills with red cells (PCV)

• How red the blood looks (Hemoglobin)

• How many cells are floating around (RBC count)

Which parameters are calculated (requires info from the measured values to plug into formula)?

• MCV

• MCH

• MCHC

• HCT

• RDW

• These values are obtained from formulas using the measured parameters, thus
  errors in measured values will yield invalid calculated values

A decrease in PCV indicates what in our patient?

▪ Percentage of whole blood that is composed of RBCs
▪ Decrease in PCV = anemia (reduced capacity to carry oxygen bc of too few RBCs)
▪ Increase in PCV = polycythemia, dehydration

Is HCT or PCV affected by agglutination?

HCT is affected, not PCV

• PCV = physically measured → not affected.
  HCT = mathematically calculated from cell counts → affected by errors like agglutination.

What are two common conditions (within the blood) that can alter hemoglobin concentration reading?

Historically assessed by lysing whole blood and analyzing the lysed blood using a spectrophotometer
– Resultant number is independent of RBC count
– Can be affected by lipidemia, jaundice

What does MCH stand for and was does this give an indication of? What is a factor that can influence this value?

Mean Cell Corpuscular Hemoglobin

• indication of the average amount of hemoglobin in each RBC

• mean weight of hemoglobin contained in the average RBC

• Can be influenced by RBC count and size

What does MCHC stand for? Why is this more accurate than MCH?

• Mean cell hemoglobin concentration

• Describes the concentration of hemoglobin in the average
  erythrocyte
  – Not affected by RBC count
  – More accurate than MCH bc not affected by RBC count

With regards to MCHC define the following terms: Normochromic, Hypochromic, Hyperchromic

• Normochromic— MCHC within reference range ; most non-regenerative anemias

• Hypochromic— MCHC below reference range ; regenerative anemias bc polychromatophils (immature RBCs) lack content

• Hyperchromic— Does not exist since RBCs cannot be super saturated with Hgb ; always artifact (measurement measures) with exception of camelids

What does RDW stand for and what is it evaluating? What is the qualitative value that speaks to the same thing as RDW?

• Red cell distribution width

• Quantitative measure of RBC anisocytosis (size variation)

• Qualitative measure is smear of anisocytosis (descriptive) which speaks to the same thing as RDW

THINK “RDW = Really Different Widths”

• If cells have really different widths, RDW goes ↑ → anisocytosis

Anisocytosis

• Variation in cell size

  • macrocytes

  • microcytes

  • both

Why can variations of RBC shape (acanthocytes, echinocytes, spherocytes, etc) be helpful from a clinical perspective?

• recognizing RBC shape variations (poikilocytosis) is hugely valuable clinically because they give clues about underlying disease processes.

• Spherocytes

  • Small, round, no central pallor

  • Suggest immune-mediated hemolytic anemia (IMHA)

• Acanthocytes

  • “spur” cell

  • Associated with liver disease

• Echinocytes

  • “burr” cells

  • can be artifact due to underfilled EDTA tubes

What is the difference between agglutination vs rouleaux? What “test” could you perform to help differentiate between the two?

• Rouleaux = Roll of coins; linear chains (inflammation/protein-related, sometimes normal).

• Agglutination = Antibodies Glue (immune-mediated, always abnormal); grape like clusters