Hematocrit and RBC Indices Quiz

Questions and Answers

What term is used to describe the small amount of plasma that remains in the RBC portion after spinning the microhematocrit?

Trapped plasma (correct)

Excess plasma

Residual plasma

Plasma retention

In which type of anemia is an increased amount of trapped plasma typically found?

Sickle cell anemia

Iron deficiency anemia

Macrocytic anemias (correct)

Aplastic anemia

What does MCV stand for in RBC indices?

Mean corpuscular volume (correct)

Maximum cellular volume

Mean cell volume

Mean corpuscule volume

What is the normal range for MCV values in femtoliters (fl)?

80 – 100 fl Signup and view all the answers

Which type of cell is referred to when MCV is less than 80 fl?

Microcyte Signup and view all the answers

What does the formula for MCV utilize as components?

PCV and RBC count Signup and view all the answers

If the MCV is greater than 100 fl, what type of cell is indicated?

Macrocyte Signup and view all the answers

Which of the following anemias is characterized by normocytic cells?

Chronic blood loss anemia Signup and view all the answers

What should be avoided when drawing blood into microhematocrit tubes?

Air bubbles Signup and view all the answers

How should the ends of the microhematocrit tubes be sealed?

With clay material at a 90° angle Signup and view all the answers

In what orientation should the sealed ends of the capillary tubes point when placed in the centrifuge?

Toward the outside Signup and view all the answers

What speed should the centrifuge be set to for the hematocrit procedure?

11000 rpm Signup and view all the answers

What should be done if the buffy coat exceeds 2% after centrifugation?

Record and note it as volume of packed WBC/plt Signup and view all the answers

What is one clinical significance of the PCV test?

It helps detect anemia or polycythemia Signup and view all the answers

What should not be included when reading the hematocrit?

The buffy coat layer Signup and view all the answers

What is the mean cell volume (MCV) calculated in conjunction with?

PCV and RBC count Signup and view all the answers

What does hematocrit measure?

The percentage of erythrocytes to the whole volume of blood Signup and view all the answers

Which component of blood settles at the bottom of the tube during centrifugation?

Red blood cells Signup and view all the answers

Which of the following is a necessary condition for hematocrit testing?

Specimens should be centrifuged within 6 hours of collection Signup and view all the answers

What type of tubes are used for capillary blood collections?

Heparinized tubes with a red tip Signup and view all the answers

What is located above the buffy coat in a centrifuged hematocrit tube?

Plasma Signup and view all the answers

Which of the following factors does NOT interfere with hematocrit determination?

Properly anticoagulated samples Signup and view all the answers

What is the purpose of the clay-type tube sealant in hematocrit testing?

To ensure proper sealing of the blood sample during centrifugation Signup and view all the answers

What instrument is used to measure hematocrit levels?

Microhematocrit reader Signup and view all the answers

What condition is associated with an increased PCV due to elevated RBC count?

Polycythemia Signup and view all the answers

What is the normal PCV range in adult females?

37 – 47 % Signup and view all the answers

Which of the following factors can cause falsely low PCV results?

Incomplete sealing of capillary tubes Signup and view all the answers

What should never be done to stop the microhematocrit centrifuge?

Applying pressure to the metal cover plate Signup and view all the answers

Which condition could result from centrifugation that is too short or at too low a speed?

Increased trapped plasma Signup and view all the answers

What effect does hemolysis of the specimen have on PCV results?

It causes falsely decreased results. Signup and view all the answers

What could happen if too much time elapses after centrifugation before removing the capillary tube?

Red cells settle out Signup and view all the answers

Which factor can falsely elevate PCV readings due to improper technique?

Inclusion of buffy coat in RBC measurement Signup and view all the answers

What does MCH stand for in hematology?

Mean Cell Hemoglobin Signup and view all the answers

What is the normal range of MCH values?

27 – 32 pg Signup and view all the answers

What type of cells are indicated by an MCH value less than 27 pg?

Hypochromic cells Signup and view all the answers

What is the formula to calculate MCH?

MCH = { Hb / RBC's } x 10 Signup and view all the answers

What condition is indicated by an MCHC value less than 30%?

Hypochromic anemia Signup and view all the answers

What is the normal range of MCHC values?

30 – 38 % Signup and view all the answers

What happens if MCHC is greater than 38%?

Indicates wrong laboratory results Signup and view all the answers

Given Hb = 15 gm/dl and RBC's = 5,000,000/mm³, what is the MCH?

30 pg Signup and view all the answers

Study Notes

Hematocrit and Packed Cell Volume (PCV)

Hematocrit (PCV) measures the percentage of erythrocytes in total blood volume (vol/vol %).
Determination involves centrifuging a blood-filled capillary tube, separating components based on density.

Principle of Hematocrit Determination

Heavier RBCs settle at the bottom during centrifugation, forming the primary layer.
WBCs and platelets form a lighter layer called the Buffy Coat above the RBCs.
The plasma sits at the top of the separated layers.

Materials Required

Venous blood anticoagulated with EDTA or capillary blood in heparinized tubes.
Capillary tubes must be filled ¾ full and centrifuged within 6 hours.
Essential items include a hematocrit centrifuge, clay sealant, and a microhematocrit reader.

Procedure Overview

Mix anticoagulated blood and fill two microhematocrit tubes manually while avoiding air bubbles.
Seal the tubes with clay and ensure a flat bottom.
Place tubes in the centrifuge, balancing them and recording their positions.
Centrifuge for 5 minutes at 11000 rpm to separate the blood components.
Read the hematocrit, excluding the Buffy Coat; if it exceeds 2%, note it as packed WBC/plt volume.

Clinical Significance of PCV

PCV is a quick test for detecting anemia and polycythemia.
It helps estimate changes in hemodilution or hemoconcentration and is vital for MCV and MCHC calculations.
Normal values: Newborns (53-65%), adult males (42-52%), adult females (37-47%).

Sources of Error in Hematocrit Measurement

Mechanical Errors:
- Incomplete sealing can lead to falsely low results.
- Excessive pressure when stopping the centrifuge can falsely elevate RBC counts.
- Insufficient centrifugation time can trap plasma, affecting readings.
- Delayed removal of capillary tubes can cause RBC settlement and inaccurate results.
Biological Errors:
- Inclusion of the Buffy Coat leads to falsely elevated results.
- Hemolysis can produce falsely decreased hemoglobin readings.
- Spun microhematocrit is generally 1.3-3% higher than electronic results due to trapped plasma, notably in specific anemias.

RBC Indices

Three key indices: MCV (Mean Corpuscular Volume), MCH (Mean Corpuscular Hemoglobin), MCHC (Mean Corpuscular Hemoglobin Concentration).
They provide insights into erythrocyte conditions and assist in diagnosing different types of anemia.

Mean Corpuscular Volume (MCV)

Indicates volume of erythrocytes: Normal range is 80-100 fl (femtoliter).
Calculated as MCV = (PCV / RBC count) x 10.
MCV classifications:
- Normocyte (80-100 fl): Normal variations, normocytic anemias.
- Microcyte (<80 fl): Indicates microcytic anemias like iron deficiency.
- Macrocyte (>100 fl): Associated with macrocytic anemias like Vitamin B12 deficiency.

Mean Corpuscular Hemoglobin (MCH)

Measures hemoglobin content per erythrocyte: Normal range is 27-32 pg (picogram).
MCH calculated as MCH = (Hb / RBC count) x 10.
MCH classifications:
- Normochromic (27-32 pg): Normal and normochromic anemias.
- Hypochromic (<27 pg): Present in hypochromic anemias like iron deficiency.
- Hyperchromic (>32 pg): Linked to hyperchromic anemias like Vitamin B12 deficiency.

Mean Corpuscular Hemoglobin Concentration (MCHC)

Determines hemoglobin volume fraction in erythrocytes: Normal range is 30-38%.
MCHC formula: MCHC = (Hb / PCV) x 100.
MCHC interpretations:
- Normochromic (30-38%): Normal and normochromic anemias.
- Hypochromic (<30%): Indicates hypochromic anemias like iron deficiency.
- MCHC >38% usually indicates lab error, impossible biological concentrations.

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Description

Test your knowledge on hematocrit values, including how to manually determine them and the influencing factors. This quiz covers key concepts of packed cell volume in whole blood and its clinical significance. Make sure to brush up on the principles and applications before starting!