Erythrogram - Automated Hematology Methods (Zimmerman)

Question 1

What is an erythrogram?

Answer 1

A set of quantitative tests to describe RBC data, part of the CBC.

Question 2

What does spun Hct measure?

Answer 2

The % of blood that’s RBC, indicating plasma character.

Question 3

What does calculated Hct use to determine its value?

Answer 3

[RBC concentration] and MCV.

Question 4

What does Hgb concentration measure?

Answer 4

Amount of hemoglobin protein in blood in g/dL, measured for absorbance.

Question 5

What does RBC concentration indicate?

Answer 5

The number of RBCs in blood.

Question 6

What does mean cell volume (MCV) measure?

Answer 6

The average size of all RBCs.

Question 7

What is MCH?

Answer 7

Mean Hgb mass per RBC, calculated from [Hgb] and [RBC].

Question 8

What does MCHC represent?

Answer 8

Mean Hgb concentration per RBC, calculated from [Hgb] and Hct.

Question 9

What does CHCM measure?

Answer 9

Mean Hgb concentration per RBC, measured by light scatter.

It is NOT calculated, so it is not affected by errors in Hgb, MCV, or RBC.

Question 10

What does RDW indicate?

Answer 10

• Width of the RBC volume distribution
• Reflects variation in RBC volumes

Red Cell Distribution Width

Question 11

What is reticulocyte concentration (RC)?

Answer 11

Concentration of reticulocytes (#/uL)

• Determined microscopically or by some hematology analyzers
• Measured by light scatter, fluorescence or absorbance.

Question 12

What does spun Hct measure?

Answer 12

Manually measures the amount of blood volume that is RBCs as a %. (aka packed cell volume)

Question 13

What does calculated Hct measure?

Answer 13

Calculates the amount of blood volume that is RBCs as a %, using mean cell volume (MCV) and RBC concentration.

Question 14

How to avoid inaccurate spun Hct results?

Answer 14

• Avoid hemolysis
• Mix the blood tube well before filling the hematocrit tube.
• Blood should be at least half of the purple top tube, too low will result in dilution of sample from EDTA, which will falsely lower the Hct volume.
• Make sure the centrifuge are set to 12000 rpm for 3 min, insufficient centrifuge will falsely increase the Hct volume.
• Finally, correctly use the chart, make sure 0 is align with where blood and clay meet, and the top of plasma is at 100.

Question 15

Difference between spun Hct from an analyzer calculated Hct?

Answer 15

• Spun Hct - blood was filled into a capillary tube and use centrifuge to separate the plasma, buffy coat and the packed red cells, and the packed RBC is read via chart. It is a quick and inexpensive test to run when automated analyzer is unavailable.
• Analyzer calculated Hct using formula (RBC count MCV)/10, are highly precise and reproducible, minimized operator error, however it is indirect, so if there are errors in RBC count or MCV will interference of final Hct result.

Question 16

What does spun Hct provide that analyzer results typically do not?

Answer 16

Plasma total protein concentration and plasma color/characteristics.

Question 17

What is being measured to yield [RBC]?

Answer 17

The number of red blood cells per unit of blood (#/uL)

Question 18

What is the relationship between Hct and anemia?

Answer 18

Decrease in Hct indicates anemia.

Question 19

What causes falsely increased [Hgb]?

Answer 19

Plasma hemolysis or lipemia.

Question 20

What is being measured to yield [Hgb]?

Answer 20

To yield [Hgb], the hemoglobin concentration is measured after RBC lysis by using light absorption.

• After RBCs are lysed, hemoglobin is released. The amount of hemoglobin pigment is measured, not directly counting RBC quantity.

Question 21

Term for decrease in [Hgb], [RBC], or Hct?

Answer 21

Anemia

Question 22

Term for increase in [Hgb], [RBC], or Hct?

Answer 22

Erythrocytosis

Question 23

What are causes for falsely increased [Hgb]?

Answer 23

Plasma hemolysis or lipemia.

Question 24

How does plasma hemolysis falsely increase [Hgb]?

Answer 24

Plasma hemolysis releases hemoglobin into the plasma. Lab analyzers measure total hemoglobin (RBC-contained + free plasma), so
the result can overestimate the actual hemoglobin concentration, giving a falsely high reading.

Question 25

How does lipemia falsely increase [Hgb]?

Answer 25

Measurement involves light absorption; the excess lipids in plasma scatter light in spectrophotometric assays, making the analyzer overestimate hemoglobin.

Question 26

How does lipemia affect hemoglobin measurement?

Answer 26

Excess lipids scatter light, leading to overestimation of hemoglobin.

Question 27

What is the difference between MCHC and MCH?

Answer 27

MCHC is mean Hgb **concentration** per RBC; MCH is mean Hgb **mass** per RBC. ## Footnote Both are calculated values!

Question 28

What is measured in MCV?

Answer 28

Mean Cell Volume * The average of all the measured RBC volumes * Used to calculate an analyzer’s Hct value * Individual cell volumes are measured by impedance or light scatter

Question 29

What is measured in MCHC?

Answer 29

Mean Hemoglobin Concentration per RBC * It is calculated from [Hgb] and Hct ## Footnote *DON’T NEED TO KNOW HOW TO CALCULATE*

Question 30

What is measured in MCH?

Answer 30

Mean Hemoglobin **mass** per RBC * It is calculated from [Hgb] and [RBC] ## Footnote *DON’T NEED TO KNOW HOW TO CALCULATE*

Question 31

Which RBC indices are affected by lipemia?

Answer 31

MCH and MCHC. ## Footnote MCV unaffected by lipemia!

Question 32

What is CHCM?

Answer 32

Cell hemoglobin concentration mean per RBC but is NOT calculated. * The Hgb of each RBC is measured by light scatter and the mean is the CHCM. * CHCM is essentially the center of the histogram of RBC Hgb concentrations.

Question 33

Is MCHC or CHCM more reliable?

Answer 33

CHCM is more reliable than MCHC because it is not calculated and therefore not affected by errors in Hgb, MCV or RBC readings.

Question 34

What do analyzers use to calculate Hct?

Answer 34

Analyzers use a PCV (packed cell volume) test to calculate Hct by reading the % of blood volume filled by RBC. * Most clinical analyzers will calculate Hct from RBC and MCV through a formula. * Generally, the Hct and Spun Hct should match within 3%, but not all companies calculate their analyzers to spun Hct (PCV).

Question 35

What does RDW measure?

Answer 35

Width of the RBC volume distribution * Variation in RBC volume = anisocytosis. * Increased RDW = more larger cells, more smaller cells, or a combination of both * Reported as a standard deviation or coefficient of variation of RBC volumes (fL or %) = statistical calculation based on a measurement * Indicator for a regenerative response!

Question 36

What do reticulocytes indicate?

Answer 36

A regenerative response in RBC production.

Question 37

What is measured by a reticulocyte concentration (RC)?

Answer 37

Concentration of reticulocytes (#/uL) * Determined microscopically or by some hematology analyzers * Reticulocytes are identifiable after staining for RNA with new methylene blue * They contain dots or aggregates of RNA * Analyzers identify them by measuring light scatter, fluorescence, or absorbance * Indicator of a regenerative response!

Question 38

What happens if excess anticoagulant is present in a blood sample?

Answer 38

It can yield a falsely low Hct by pulling water out of RBCs, causing them to shrink.

Question 39

What steps that be taken to increase the reliability of hematology analyzer results?

Answer 39

* Maintenance and quality assurance (QA) * Smear evaluations required for complete CBC

Question 40

What is the relationship between qualitative and quantitative erythrocyte findings?

Answer 40

* Qualitative findings come from manually counting RBCs and describing morphology. * Quantitative findings come from calculations or analyzer measurements.

Question 41

What may be seen microscopically if RBCs have low MCHC?

Answer 41

Swollen RBCs due to excess water absorption. ## Footnote Having a lower mean cell [Hgb] means there is less Hgb compared to the water/solution of the RBC.

Question 42

What is the microscopic equivalent of increased RDW?

Answer 42

Anisocytosis (either macrocytosis or microcytosis)

Question 43

What is the relationship between reticulocyte concentration and polychromasia?

Answer 43

ALL polychromaphils are reticulocytes, but not all reticulocyte are polychromaphils, not all reticulocyte appear as polychromasia during wright stain (quick diff), so increase concentration of reticulocyte = increase number of polychromasia