reticulocytes
TRANSCRIPT
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DEFINITION
Reticulocytes are immature red blood cells, typically composing about 1% of the red cells in the human body.
PHYSIOLOGY
1. Reticulocytes develop and mature in the red bone marrow .2. Circulate for about 1 day in the blood stream before developing into mature RBCs3. Reticulocytes do not have a cell nucleus. 4. They are called reticulocytes because of a reticular (mesh-like) network of ribosomal RNA that
becomes visible under a microscope with certain stains such as new methylene blue.
THERE ARE THREE MAIN PARAMETERS DESCRIBING RETICULOCYTES IN OUR BODY:
1. RETICULOCYTES PERCENTAGE. (RETIC COUNT)
2. RETICULOCYTE INDEX. (RI)
3. CORRECTED RETIC COUNT OR RETICULOCYTE PRODUCTION INDEX (RPI)
MEASURING RETICULOCYTE PERCENTAGE (RETIC COUNT)
Specimen: EDTA anti-coagulated whole blood (lavender-top bottle if using the Vacutainer).
Fluorescent Staining
1. Fluorescent dye like Thiazole Orange or Polymethine marks intracellular RNA and DNA.2. LASER counters are used to count cell showing fluorescence.3. Three types of cells are found:-
RBCs: neither RNA nor DNA
WBCs: a large amount of DNA
Reticulocytes: only RNA
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Routine Staining
1. Reticulocytes appear slightly bluer than other red cells when looked at with the normal Romanowsky stain.
2. Reticulocytes are also slightly larger, which can be picked up as a high MCV (mean corpuscular volume).
Interpretation
Normal Range: 0.5% to 1.5%. (Variable in different labs) In anemia “Reticulocyte Percentage” should be higher than "normal" if the bone marrow's ability to
produce new blood cells remains intact. When there is an increased production of red blood cells to overcome chronic or severe loss of
mature red blood cells, such as in a haemolytic anaemia, people often have a markedly high number and percentage of reticulocytes.
A very high number of reticulocytes in the blood can be described as reticulocytosis. Reticulocytopenia, or "aplastic crisis", is the medical term for an abnormal decrease of
reticulocytes in the body Abnormally low numbers of reticulocytes can be attributed to:
o Chemotherapy o Aplastic anaemiao Pernicious anaemiao Bone marrow malignancies,o Problems of erythropoietin production, o Various vitamin or mineral deficiencies (B9, B12, iron)o Disease states (anaemia of chronic disease) and o Other causes of anaemia due to poor RBC production.
Thus, calculating the reticulocyte production index is an important step in understanding whether the reticulocyte count is appropriate or inappropriate to the situation.
The number of reticulocytes is a good indicator of bone marrow activity, because it represents recent production.
The reticulocyte count and the reticulocyte production index can be calculated from it, which can be used to determine whether a production problem is contributing to the anaemia, and can also be used to monitor the progress of treatment for anaemia.
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RETIC INDEX AND RETICULOCYTE PRODUCTION INDEX
The Reticulocyte production index (RPI, also called a corrected reticulocyte count) is a calculated value used in the diagnosis of anemia.
This calculation is necessary because the raw reticulocyte count is misleading in anemic patients. The problem arises because the reticulocyte count is not really a count but rather a percentage: it reports the number of reticulocytes as a percentage of the number of red blood cells.
In anemia, the patient's red blood cells are depleted, creating an erroneously elevated reticulocyte count.
The idea of the RPI is to assess whether the bone marrow is producing an appropriate response to an anemic state. Reticulocyte production should increase in response to any loss of red blood cells.
It should increase within 2-3 days of a major acute hemorrhage, for instance, and reach its peak in 6-10 days.
The reticulocyte percentage index may find new use as a more reliable detector of erythropoietin-doping in athletes. The use of this method is referred to as "biological passport."
Calculation
Reticulocyte Production Index is calculated as follows:
1.
A value of 45 is usually used as a normal hematocrit.
2. The next step is to correct for the longer life span of prematurely released reticulocytes in the blood--a phenomenon of increased red blood cell production. This relies on a table:
Hematocrit (%) Retic survival (days) = maturation correction
36-45 1.0
26-35 1.5
16-25 2.0
15 and below 2.5
So, in a person whose reticulocyte count is 5%, hemoglobin 7.5 g/dL, hematocrit 25%, the RPI would be:
4
→ RPI 1.4
Alternatively some books provide the following formula:
Interpretation
The reticulocyte index (RI) should be between 1.0% and 2.0% for a healthy individual.
RI < 1% with anemia indicates decreased production of reticulocytes and therefore red blood cells.[2]
RI > 2% with anemia indicates loss of red blood cells (destruction, bleeding, etc) leading to increased compensatory production of reticulocytes to replace the lost red blood cells.
ADOPTED FROM WIKIPEDIA