RBC Indices & Testing

What are the tests performed in hematology associated with erythrocytes?

RBC count, Hemoglobin (Hgb), Hematocrit (Hct), Mean Corpuscular Volume (MCV), Mean Corpuscular Hemoglobin (MCH), Mean Corpuscular Hemoglobin Concentration (MCHC), Red Cell Distribution Width (RDW), Reticulocyte count, Erythrocyte Sedimentation Rate (ESR).

What is the normal range for RBC count, Hgb, Hct, MCV, MCH, MCHC, RDW, and retic count?

Normal ranges vary by laboratory but generally: RBC count (4.5-5.9 million cells/µL), Hgb (13.5-17.5 g/dL), Hct (38.8-50%), MCV (80-100 fL), MCH (27-31 pg), MCHC (32-36 g/dL), RDW (11.5-14.5%), retic count (0.5-1.5%).

What methods are used to enumerate blood cells in hematology?

Electrical impedance and laser methods.

How is a manual RBC count performed?

A manual RBC count is performed using a hemocytometer and a diluted blood sample.

What is the principle of the cyanmethemoglobin method for hemoglobin determinations?

The cyanmethemoglobin method involves converting hemoglobin to cyanmethemoglobin, which can be measured spectrophotometrically.

What is packed cell volume (hematocrit)?

Packed cell volume (HCT) is the percentage of blood volume that is occupied by red blood cells.

How is hematocrit determined on automated hematology analyzers?

Automated analyzers calculate hematocrit based on the volume of red blood cells relative to the total blood volume.

What is the purpose of MCV?

MCV indicates the average size of red blood cells (normocytic)

What is the purpose of MCH?

MCH measures the average amount of hemoglobin per red blood cell.

What is the purpose of MCHC?

MCHC reflects the average concentration of hemoglobin in a given volume of packed red blood cells.

How is RDW determined and what is its purpose?

RDW is determined by measuring the variation in red blood cell size; it helps assess anisocytosis.

Why can RDW only increase and not decrease?

RDW can only increase because it reflects the presence of greater variability in red blood cell sizes, which cannot be reversed.

What is the purpose of reticulocyte counts?

Reticulocyte counts assess bone marrow function and the production of new red blood cells.

How is a manual reticulocyte count performed?

A manual reticulocyte count is performed by staining a blood smear and counting reticulocytes under a microscope.

What calculations can be performed with reticulocyte counts?

Relative retic counts, Absolute Reticulocyte Count (ARC), Corrected Reticulocyte Count (CRC), and Reticulocyte Production Index (RPI).

When should ARC, CRC, and RPI be performed?

These should be performed when evaluating bone marrow response to anemia.

What are shift retics?

Shift retics are immature red blood cells released from the bone marrow in response to increased demand for red blood cells.

What is the purpose of an ESR and how is it performed?

The ESR measures the rate at which red blood cells settle in a tube over a specified period, indicating inflammation.

What are the two types of manual tubes used in testing a Sed rate?

Westergren and Wintrobe tubes.

What is the most commonly used stain in the hematology lab?

Wright stain.

What are the components of Wright stain and their functions?

Wright stain contains eosin (acidic dye) for staining cytoplasmic components and methylene blue (basic dye) for staining nucleic acids.

What is the rule of three in hematology?

The rule of three states that Hgb should be approximately three times the RBC count and Hct should be approximately three times the Hgb.

How can you describe the blood picture from a peripheral blood smear given CBC values?

The blood picture can be described based on cell morphology, size, shape, and presence of abnormalities.

How is a corrected WBC calculation performed?

Corrected WBC count is calculated by adjusting the total WBC count based on the percentage of nucleated red blood cells.

What does CBC stand for in medical testing?

Complete Blood Count

Which white blood cell type is included in the WBC differential?

Neutrophils, lymphocytes, monocytes, eosinophils, basophils

What are the tests associated with erythrocytes in a CBC?

Erythrocyte Sedimentation Rate, Reticulocyte Count, Blood Smear Examination

What is the purpose of a blood smear examination?

To observe RBC, platelet, and WBC morphology and count nucleated RBCs.

What is the difference between the Conventional and International systems in hematology?

Conventional is primarily used in the US, while International is used worldwide.

What is the reference range for male RBC count?

4.5 x 10^12/L - 5.5 x 10^12/L or 4,500,000 - 5,500,000 cells/mm3

What is the reference range for female RBC count?

4.0 x 10^12/L - 5.0 x 10^12/L or 4,000,000 - 5,000,000 cells/mm3

What equipment is used in a manual RBC count?

Unopette for dilution and Hemacytometer for counting.

What is the first step in performing a manual RBC count?

Dilute whole blood with diluent using a Unopette.

What is the size of Box 1 in the hemacytometer counting grid?

1mm x 1mm, containing 16 secondary squares.

How many squares are counted for WBCs in the hemacytometer?

4 corner squares in Box 1.

How many squares are counted for RBCs in the hemacytometer?

4 corner squares and 1 center square in Square 5.

What is the standard cell counting formula?

of cells counted / (# of squares x L x W x D) x dilution factor = cells/mm3

What is the depth measurement used in the RBC counting calculation?

0.1mm (coverslip to slide depth).

What is the average RBC count if 1,023 RBCs are counted on both sides of the hemacytometer?

511.5 RBCs.

What does MPV stand for in CBC results?

Mean Platelet Volume

What is the purpose of a WBC differential?

To count and identify 100 WBCs.

What is HGB in CBC results?

Hemoglobin

What does RDW stand for?

Red Cell Distribution Width

What does HCT represent in a CBC?

Hematocrit

What is the normal RBC count in cells/mm3?

5,115,000 cells/mm3

What are the two major methods for automated RBC count?

Electrical impedance and laser methods (optical scatter).

How does the electrical impedance method work for counting RBCs?

RBCs suspended in saline flow through an aperture between two electrodes, interrupting the current; each interruption is counted and its size is proportional to the cell size.

What is the principle behind laser methods for RBC counting?

Diluted blood is forced into a single line, and a laser beam detects scattered light from the cells, converting it into electrical pulses proportional to the number of cells.

What is the reference range for hemoglobin (Hgb) in males?

14-18 g/dL.

What is the reference range for hemoglobin (Hgb) in females?

12-16 g/dL.

What is the manual method for measuring hemoglobin concentration?

Conversion of hemoglobin to cyanmethemoglobin using potassium cyanide and potassium ferricyanide.

What is the procedure for the manual hemoglobin measurement?

Add EDTA specimen to Drabkin's reagent, measure cyanmethemoglobin on a spectrophotometer against known standards.

What is the reference range for hematocrit (Hct) in males?

42-52%.

What is the reference range for hematocrit (Hct) in females?

35-46%.

What does hematocrit measure?

The ratio of the volume occupied by RBCs to the volume of whole blood.

What are the three RBC indices?

MCV, MCH, and MCHC.

What is the reference range for MCV?

80-100 fL.

What does MCV express?

The average volume of an RBC, calculated as Hematocrit x 10 / RBC.

What is the reference range for MCH?

28-34 pg.

What does MCH express?

The average weight of hemoglobin in picograms, calculated as Hemoglobin x 10 / RBC.

What is the reference range for MCHC?

32-36% or g/dL.

What does MCHC represent?

The average concentration of hemoglobin in each individual RBC, calculated as HBG x 100 / HCT.

What is the reference range for RDW?

11.5-14.5%.

What does RDW measure?

The variation in cell size (anisocytosis) based on the histogram of red cell size.

What are the variations of reticulocyte count?

Relative reticulocyte count, corrected reticulocyte count, reticulocyte production index (RPI), and absolute reticulocyte count.

What is the reference range for relative reticulocyte count in adults?

0.5-1.5%.

What does a relative reticulocyte count indicate?

It detects RBCs still containing RNA, monitors erythropoiesis, and reflects the bone marrow's response to anemia.

What does a reticulocyte count of 3.0% indicate?

It suggests an increased production of RBCs, possibly in response to anemia.

What is the Corrected Retic Count (CRC)?

The CRC is a percentage of circulating RBCs adjusted for.

What is the formula for the Corrected Retic Count?

CRC = retic % x Hct / 45

How is the CRC calculated for John Doe with a retic count of 3.0% and Hct of 22%?

CRC = 3.0% x 22 / 45 = 1.5%.

What is the purpose of the Retic Production Index (RPI)?

The RPI measures erythropoietic activity when stress retics are present, accounting for the longer lifespan of shift retics.

How is the RPI calculated?

RPI = CRC / correction factor.

What does an RPI value of <2 indicate?

It indicates normal bone marrow activity, while a higher value suggests the bone marrow is correcting for anemia.

What is the Absolute Retic Count (ARC)?

The ARC is the actual number of retics in 1L of whole blood, calculated as ARC = retic % x (RBC count x 10^12) / 100.

What is the reference range for the Absolute Retic Count?

The reference range is 25-75 x 10^9/L, indicating normal production.

How is the ARC calculated for John Doe with a retic count of 3.0% and RBC count of 2.5 x 10^12?

ARC = 3.0% x (2.5 x 10^12) / 100 = 75.0 x 10^9/L.

What does an increased Erythrocyte Sedimentation Rate (ESR) indicate?

An increased ESR indicates inflammation.

What is the typical reference range for ESR?

The reference range for ESR is usually less than 10 mm/hr, depending on age.

What is the procedure for measuring ESR?

Anticoagulated blood is allowed to stand undisturbed at room temperature, causing RBCs to settle at the bottom of the tube.

What are the two methods for performing an ESR test?

The two methods are manual (Westergren and Wintrobe) and automated systems.

What is a well-made peripheral blood smear?

A well-made smear shows RBCs that are slightly overlapping, allowing for proper examination.

What are the characteristics of an unacceptable peripheral blood smear?

An unacceptable smear may be too thin (RBCs far apart) or too thick.

What is the significance of shift retics in the context of anemia?

Shift retics are released early from the bone marrow during anemia and have a longer lifespan in peripheral blood.

What is the average lifespan of normal retics in the peripheral blood?

Normal retics spend about 1 day in peripheral blood.

What is the average lifespan of shift retics in peripheral blood?

Shift retics spend about 2.5 days in peripheral blood.

Why is it important to correct the retic count in the context of anemia?

Correcting the retic count provides a more accurate assessment of erythropoietic activity and RBC production.

What happens to the retic count when the bone marrow compensates for anemia?

The retic count may be elevated due to the accumulation of shift retics, even if corrected.

What is the correction factor used in the CRC formula?

The correction factor is derived from the average normal hematocrit (Hct), typically assumed to be 45%.

What does a CRC value of 1.5% indicate for John Doe?

It indicates a corrected retic count after accounting for his low Hct of 22%.

What is the significance of the RBC count in relation to retic counts?

The RBC count is essential for calculating both the CRC and ARC, providing context for reticulocyte production.

What is the purpose of staining blood smears?

To identify cells and recognize morphology easily through a microscope.

What are the common stains used in blood smear examination?

Wright stain or Wright-Giemsa stain.

What components are in Wright stain?

Eosin, methylene blue, methanol, and buffers.

How are cells fixed to the slide during staining?

Cells are fixed to the slide by methanol.

What does methylene blue stain in blood cells?

It stains acidic cellular components, such as RNA, blue.

What does eosin stain in blood cells?

It stains basic components, such as hemoglobin or eosinophilic granules, red.

What is the normal range for MCV (Mean Corpuscular Volume)?

80-100 fL.

What does an increased MCV indicate?

Macrocytic anemia (>100 fL).

What does a decreased MCV indicate?

Microcytic anemia (<80 fL).