This document discusses reticulocytes, which are immature red blood cells that spend 1-3 days maturing in the bone marrow before circulating in the bloodstream. Key points include: - Reticulocytes have residual RNA that allows them to be stained and counted to assess bone marrow activity. - An elevated reticulocyte count indicates the bone marrow is responding to anemic stress by increasing red blood cell production. - The reticulocyte count is used to evaluate bone marrow function and health in conditions like anemia, blood loss, or following chemotherapy/radiation.

1. RAJESH MOHESS, CLT. A.P.

2. RETICULOCYTE
The reticulocyte is the cell stage immediately before the mature
erythrocyte.
This cell spends 2 to 3 days maturing in the bone marrow before it is
released into the peripheral circulation, where it spends an additional
day of maturation.
Acidophilic erythroblast (NRBC) expels the nucleus and becomes the
reticulocyte
Bone marrow macrophages phagocytize and digest the expelled nucleus.
The size of reticulocyte is about 8 μm
RNA-synthesizing ribosomes, present in reticulocytes, are stained blue
On its membrane, the reticulocyte has receptors for transferrin so that
iron can enter the cell. Due to the transferrin it is also referred to as
“sticky” cell

3. RETICULOCYTE
The reticulocyte count is the most effective measure of
erythropoietic activity.
Reticulocyte counts are a reflection of bone marrow health
or injury
Reticulocytes are red cells that are non-nucleated and that
contain remnant RNA material, reticulum.
Reticulum cannot be visualized by Wright’s stain; to be
counted and evaluated, reticulocytes must be stained with
supravital stains, like new methylene blue or brilliant cresyl
blue.

4. RETICULOCYTE
Because the bone marrow has the capacity to expand its
production up to 7 times the normal rate, an elevated
reticulocyte count or reticulocytosis is the appropriate
response in anemic stress
Reticulocytes will be seen in the peripheral smear as
polychromatophilic macrocytes (large, bluish cells)
Nucleated red blood cells may also be visualized in the
peripheral smear as the bone marrow races to deliver
cells prematurely at a rapid rate.

5. RETICULOCYTE
Reagents and Equipment
1. New Methylene Blue (Supravital Stain)
2. Test tubes
3. Microscope slides with a frosted end
4. Microscope with x100 (oil immersion objective)
5. Transfer pipettes

6. RETICULOCYTE
Procedure
1. Mix 4 drops of New Methylene Blue with 4 drops of
patient’s blood.
If the specimen is a small amount (such as a Microtainer),
add an equal amount of stain to the Microtainer after the
CBC has been completed.
2. Let the specimen mix for 10 to 15 minutes.
Make a wedge smear and let it air dry. Label the smear
3. Allow the smear to completely dry and read under the
microscope using x100 oil immersion.
a. Count the number of reticulocytes in 1000 cells (10 fields).

7. RETICULOCYTE
Use the following formula to calculate the percentage of
reticulocytes
Number of Retic = (# retic per 1000 red cells x 100)/1000
Note: 1000 red cells = 10 fields
Example: 35 x100/1000 = 3.5%
OR
Number of retic counted divided by 10
Example; 35/10 = 3.5 %

8. RETICULOCYTE

9. RETICULOCYTE
Normal Values
Adults: 0.5% to 2.0%
Infants: 2.0% to 6.0%

10. RETICULOCYTE
Limitations
1. Recent blood transfusion can interfere with accurate
reticulocyte results.
2. Mishandling, contamination, or inadequate refrigeration
of the sample can interfere and cause inaccurate test results.
3. Red cell inclusions such as Heinz bodies, siderocytes, and
Howell-Jolly bodies can be mistaken for reticulocytes.
If these are counted as reticulocytes, they will falsely
increase the reticulocyte count.
Inclusions should be confirmed with Wright’s stain

11. RETICULOCYTE
Inceased Reticulocyte count
Increased reticulocyte counts indicate increased
erythropoietic activity usually as the bone marrow
compensates in response to anemic stress
Increased count associated with:
1. Rapid blood loss
2. High elevation
3. Hemolytic anemias
4. Medications such as levodopa, malarial medications,
corticotrophin, and fever-reducing medications
5. Pregnancy

12. RETICULOCYTE
Decreased Reticulocyte count (<0.5%)
Low reticulocyte counts indicate decreased
erythropoietic activity
Decreased count associated with:
1. Aplastic anemia (where the production of either
white or red cells or both is seriously impaired)
2. Exposure to radiation or radiation therapy
3. Chronic infection
4. Medications such as chloramphenicol, methotrexate
and other chemotherapy medications
5. Untreated pernicious anemia/megaloblastic anemia

13. RETICULOCYTE
Calculation of corrected reticulocyte
The reticulocyte count is most often expressed as a
percentage of total red cells.
In states of anemia, the reticulocyte percentage is not a
true reflection of reticulocyte production.
A correction factor must be used so as not to
overestimate marrow production
Because each reticulocyte is released into whole blood
containing few RBCs and a low hematocrit (Hct), the
percentage of reticulocyte will be increased.

14. RETICULOCYTE
Calculation of corrected reticulocyte
The corrected reticulocyte count may be calculated by the
following formula:
Corrected reticulocyte count = (Retic % x patient’s Hct %) divided
by Average normal Hct
Note: Average normal Hct is 45 for men and 42 for women
Example:
Uncorrected retic % = 5.0%
Patient Hct = 35.0% (male)
Average normal hct for male = 45%
Corrected retic % = (5.0% x 35%) / 45 = 3.89%
Corrected retic % = 175/45 = 3.89 %

15. RETICULOCYTE
THE END