Medical Laboratory Procedures

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Questions and Answers

What is the significance of Howell-Jolly bodies in blood samples?

They indicate the presence of hemolytic anemia.

They are associated with iron deficiency.

They are round nuclear fragments typically found singly. (correct)

They represent multiple inclusions in red blood cells.

What type of stain is used to identify Pappenheimer bodies?

Wright Giemsa stain

Prussian blue stain (correct)

Hematoxylin and eosin stain

Supravital stain

Which condition requires adjusting the dye to blood proportion during reticulocyte counting?

Hypoxia

Thrombocytopenia

Anemia or polycythemia (correct)

Leukemia

What common error could affect the accuracy of reticulocyte counts?

Improper mixing of blood and stain Signup and view all the answers

What characteristic distinguishes Heinz bodies from Howell-Jolly bodies?

Heinz bodies are multiple inclusions within a single cell. Signup and view all the answers

What is the primary factor contributing to reticulocytes settling at the top of the mixture during incubation?

Lower specific gravity of reticulocytes Signup and view all the answers

Which statement about moisture affects the preparation of blood smears?

Moisture can lead to poor drying of the slide. Signup and view all the answers

What effect does polycythemia have on red blood cell appearance?

Large red blood cells Signup and view all the answers

What is the purpose of using the Miller disc in counting reticulocytes?

To improve the accuracy of the counting process Signup and view all the answers

How many red blood cells (RBCs) should be counted to satisfy the College of American Pathologists (CAP) standard?

1000 RBCs Signup and view all the answers

What method is employed in the procedure described for counting reticulocytes?

Only the dry method Signup and view all the answers

What is the minimum number of cells that should be counted in the small square to ensure accuracy?

112 cells Signup and view all the answers

When counting reticulocytes, what is factored when calculating the reticulocyte count using the Miller disc?

Each reticulocyte is counted as both an RBC and a reticulocyte Signup and view all the answers

What ratio represents the area of the larger square to that of the smaller square?

9:1 Signup and view all the answers

Which of the following counting areas is used for RBCs and reticulocytes respectively?

Smaller square for RBCs, larger square for reticulocytes Signup and view all the answers

What is required for two laboratorians regarding the counted values?

The values should differ by no more than 20% Signup and view all the answers

What happens if fewer than 112 cells are counted in the small square?

The count is considered invalid Signup and view all the answers

What does the absolute reticulocyte count (ARC) represent?

The number of reticulocytes in a specified volume of blood Signup and view all the answers

Which of the following inclusions appear in supravital stain but do not appear in Wright Giemsa stain?

Heinz bodies and reticulocytes Signup and view all the answers

What could lead to an erroneous reticulocyte percentage count?

Fluctuations in the total number of circulating erythrocytes Signup and view all the answers

Why is the expression of reticulocytes in absolute terms becoming preferred?

It accounts for variations caused by the quantity of erythrocytes. Signup and view all the answers

Heinz bodies are associated with which condition?

Precipitated hemoglobin Signup and view all the answers

How is the corrected reticulocyte count calculated for clinical interpretation?

By adjusting the observed count to a normal packed RBC volume Signup and view all the answers

What is the primary purpose of new methylene blue stain in the reticulocyte counting procedure?

To stain reticulocytes for visualization Signup and view all the answers

What is a typical average normal hematocrit value considered for correction calculations?

45% Signup and view all the answers

How long should the blood and stain mixture be incubated at room temperature?

3 to 10 minutes Signup and view all the answers

What is the reason for remixing the preparation after staining the blood?

To ensure even distribution of the stain Signup and view all the answers

How are reticulocyte counts traditionally expressed?

As a percentage of total circulating erythrocytes Signup and view all the answers

What is the first step in preparing the new methylene blue solution?

Weigh out 0.5 g of new methylene blue N Signup and view all the answers

Why is potassium oxalate included in the new methylene blue solution preparation?

To act as an anticoagulant Signup and view all the answers

How should the blood sample be initially drawn for reticulocyte counting?

In heparinized tubes or mixed with stain immediately Signup and view all the answers

What is the final step in preparing the stained blood sample?

Preparing two wedge films Signup and view all the answers

What is the required volume of blood and new methylene blue stain for the test?

50 mcL each Signup and view all the answers

What is the essential characteristic that distinguishes reticulocytes from Heinz bodies?

Reticulocytes exhibit laments while Heinz bodies do not. Signup and view all the answers

In dealing with G6PD deficiency, what is indicated by the presence of Heinz bodies?

Formation as a reaction to hemolysis. Signup and view all the answers

What method is used to ensure identification of Heinz bodies effectively?

Vital staining. Signup and view all the answers

What specific action should be taken after placing a blood drop on a slide during the wet method?

Press down and remove excess with cotton. Signup and view all the answers

What type of blood cells are described as 'bite cells'?

Cells pitted due to splenic processing. Signup and view all the answers

At what stage should oil immersion be utilized in the dry method of blood sample preparation?

After the smear has dried. Signup and view all the answers

Which of the following stains is used specifically in the context of pitted RBCs?

Coomassie Brilliant Blue. Signup and view all the answers

What is the main purpose of using a vital stain in the wet method?

To improve the visibility of cells in a smear. Signup and view all the answers

Study Notes

Reticulocyte Count Procedure

Prompt testing after blood collection is crucial for accuracy.
Mix equal parts of blood and new methylene blue stain (50 µL each), incubate for 3 to 10 minutes to allow reticulocytes to absorb the stain.
Stained smears retain color for extended periods, facilitating observation.

Reagent Preparation

New methylene blue solution, known as Methylene Blue N, requires precise preparation:
- Mix 0.5 g new methylene blue N, 1.4 g potassium oxalate, and 0.8 g sodium chloride in 100 mL volumetric flask and dilute to the calibration mark with distilled water.

Counting Procedure

Count 1000 RBCs using a microscope with oil immersion; reticulocytes are counted alongside.
Employ the Miller ocular disc to expedite counting, with reticulocytes present in the larger square.
Accuracy is improved when a second laboratorian verifies the count, ensuring values align within a 20% range.

Calculation of Reticulocyte Count

Reticulocyte results calculated by multiplying the number of counted reticulocytes by 0.1.
At least 112 cells must be counted in the smaller square for adherence to CAP standards.

Types of Counting Methods

The dry method involves creating a smear for counting under oil immersion.
In the wet method, a drop of blood is placed on a slide with a cover slip.

Error Sources in Counting

Adjust dye-to-blood proportions based on patient anemia or polycythemia for accurate reticulocyte representation.
Mixing blood with stain is essential before smear preparation to prevent settling of reticulocytes.
Environmental moisture can create refractile areas on slides, mimicking reticulocytes.

Reticulocyte Quality Control

Reticulocyte counts are traditionally expressed as a percentage; however, fluctuations in total erythrocyte quantity may affect results.
Absolute reticulocyte count (ARC) represents the true count in 1 L of blood, giving a more reliable indication of reticulocyte status.

Correction for Anemia

Corrections for anemia factor in the hematocrit, typically considered normal at 45%.
Different methods, including mathematical correction, adjust observed reticulocyte counts for accurate interpretation in clinical settings.

Reticulocyte Characteristics

Reticulocytes contain RNA and can be distinguished from other inclusions under specific stains.
Howell-Jolly bodies are singular nuclear remnants visible with Wright Giemsa stain, while Heinz bodies, which indicate hemoglobin precipitates, are seen in supravital stains.

Reticulocyte Variability

Reticulocyte counting methods differ; both wet and dry methods provide opportunities for detailed analysis of blood quality and quantity.
Fluorocytometric methods may also be used for advanced counting and analysis.

Hemolytic Anemia Indicators

Heinz bodies form under glucose-6-phosphate dehydrogenase (G6PD) deficiency and may appear in thalassemia.
Bite cells, resulting from spleen action on RBCs with Heinz bodies, are important in identifying specific hemolytic anemias.

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Description

This quiz covers the procedures for preparing and staining blood samples, particularly focusing on the use of heparinized tubes and new methylene blue stain for reticulocyte counts. Understanding these techniques is vital for accurate diagnostics in hematology.