Reticulocyte index: Difference between revisions
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{{CMG}} | {{CMG}}; Associate Editor(s)-In-Chief: [[Priyamvada Singh|Priyamvada Singh, M.D.]] [mailto:psingh13579@gmail.com] | ||
==Overview== | |||
* [[Reticulocyte]]s are newly-produced red blood cells. They are slightly larger than totally mature red blood cells, and have some residual ribosomal [[RNA]]. The presence of RNA allows a visible blue stain to bind or, in the case of fluorescent dye, result in a different brightness. This allows them to be detected and counted as a distinct population. | |||
* 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. | |||
* If reticulocyte production is not raised in response to anemia, then the anemia may be due to an acute cause with insufficient time to compensate, or there is a defect with red blood cell production in the bone marrow. | |||
* Marrow defects include nutritional deficiencies (i.e. iron, folate, or B12) or insufficient [[erythropoietin]], the stimulus for red blood cell production. | |||
* Reticulocyte Production Index is calculated as follows: | |||
* The degree of anemia (done by normalizing hematocrit of 45%) | |||
* Reticulocyte maturation time (RMT) | |||
* The Reticulocyte maturation time is 1.0 days for a hematocrit of 45 % to 2.5 days for a hematocrit of 15 %: | |||
* Reticulocyte production index = Reticulocytes % x (HCT / 45) x (1 / RMT) | |||
* The reticulocyte index (RI) should be between 1.0 and 2.0 for a healthy individual. | |||
* RI < 2 with anemia indicates decreased production of reticulocytes and therefore red blood cells. | |||
* 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.** Value of 45 is usually used as a normal hematocrit. | |||
** So,in a person whose reticulocyte count is 5%, hemoglobin 7.5 g/dL, hematocrit 25%, the RPI would be: | |||
'''5 x [corrected retic count]/[maturation correction] = 5 x (25/45) /2 = 1.4''' | |||
''5 x [corrected retic count]/[maturation correction] = 5 x (25/45) /2 | |||
==References== | ==References== | ||
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==External links== | ==External links== | ||
*[http://medcalc3000.com/ReticProdIndex.htm Medical Calculator] Online RPI calculator, "for educational purposes only". | *[http://medcalc3000.com/ReticProdIndex.htm Medical Calculator] Online RPI calculator, "for educational purposes only". | ||
[[Category:Blood]] [[Category:Hematology]] | [[Category:Blood]] [[Category:Hematology]] | ||
{{WikiDoc Help Menu}} | {{WikiDoc Help Menu}} | ||
{{WikiDoc Sources}} | {{WikiDoc Sources}} | ||
Latest revision as of 17:54, 2 November 2012
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-In-Chief: Priyamvada Singh, M.D. [2]
Overview
- Reticulocytes are newly-produced red blood cells. They are slightly larger than totally mature red blood cells, and have some residual ribosomal RNA. The presence of RNA allows a visible blue stain to bind or, in the case of fluorescent dye, result in a different brightness. This allows them to be detected and counted as a distinct population.
- 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.
- If reticulocyte production is not raised in response to anemia, then the anemia may be due to an acute cause with insufficient time to compensate, or there is a defect with red blood cell production in the bone marrow.
- Marrow defects include nutritional deficiencies (i.e. iron, folate, or B12) or insufficient erythropoietin, the stimulus for red blood cell production.
- Reticulocyte Production Index is calculated as follows:
- The degree of anemia (done by normalizing hematocrit of 45%)
- Reticulocyte maturation time (RMT)
- The Reticulocyte maturation time is 1.0 days for a hematocrit of 45 % to 2.5 days for a hematocrit of 15 %:
- Reticulocyte production index = Reticulocytes % x (HCT / 45) x (1 / RMT)
- The reticulocyte index (RI) should be between 1.0 and 2.0 for a healthy individual.
- RI < 2 with anemia indicates decreased production of reticulocytes and therefore red blood cells.
- 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.** Value of 45 is usually used as a normal hematocrit.
- So,in a person whose reticulocyte count is 5%, hemoglobin 7.5 g/dL, hematocrit 25%, the RPI would be:
5 x [corrected retic count]/[maturation correction] = 5 x (25/45) /2 = 1.4
References
- ^ Adamson JW, Longo DL. Anemia and polycythemia. in: Braunwald E, et al. Harrison's Principles of Internal Medicine. (15th Edition). McGraw Hill (New York), 2001.
- ^ Hoffbrand AV, et al. Essential Haematology. (Fourth Edition) Blackwell Science (Oxford), 2001.
External links
- Medical Calculator Online RPI calculator, "for educational purposes only".