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| [[Image:Polychromatic erythrocyte.png|thumb|120px|[[Reticulocyte]]]]
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| [[Image:Erythrocyte.png|thumb|120px|[[Erythrocyte]]]]
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| 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.
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| <ref>{{cite journal|last=Callaway|title=Racing Just To Keep Up|journal=Nature|year=2011|volume=475|pages=283|doi=10.1038/475283a}}</ref>
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| ==Physiology==
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| [[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.<ref name="Adamson">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.</ref>
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| 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.<ref>Hoffbrand AV, et al. ''Essential Haematology.'' (Fourth Edition) Blackwell Science (Oxford), 2001.</ref> 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. [[Reticulocytopenia]], or "aplastic crisis", is the medical term for an abnormal decrease of reticulocytes in the body
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| 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."
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| ==Calculation of RPI==
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| Reticulocyte Production Index is calculated as follows:
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| '''1.'''<math>Retic Index = Retic Count * {Hematocrit \over Normal Hematocrit}</math>
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| A value of 45 is usually used as a normal hematocrit.<ref name="urlUAB Hematopathology">{{cite web |url=http://peir.path.uab.edu/heme/messages/637/648.html |title=UAB Hematopathology |work= |accessdate=2009-02-07}}</ref>
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| '''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:
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| {| class="wikitable"
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| |-
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| ! Hematocrit (%)
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| ! Retic survival (days) = maturation correction
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| |-
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| | 36-45
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| | 1.0
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| |-
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| | 26-35
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| | 1.5
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| |-
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| | 16-25
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| | 2.0
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| |-
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| | 15 and below
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| | 2.5
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| |}
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| '''So,''' in a person whose reticulocyte count is 5%, hemoglobin 7.5 g/dL, hematocrit 25%, the RPI would be:
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| <math>RPI = {Retic Index \over Maturation Correction}</math> '''→ RPI ''' <math>= {{5 * {25 \over 45}} \over 2} = </math>'''1.4'''
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| Alternatively some books provide the following formula:
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| <math>RPI = Retic Count * {Hemoglobin(observed) \over Normal Hemoglobin}*0.5</math>
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| ==Interpretation==
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| *The reticulocyte index (RI) should be between 1.0% and 2.0% for a healthy individual.
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| *RI < 2% with anemia indicates loss of red blood cells, but decreased production of reticulocytes (ie, an inadequate response to correct the anemia) and therefore red blood cells.<ref name="Adamson"/>
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| *RI > 3% with anemia indicates loss of red blood cells (from causes such as destruction, bleeding, etc.), with an increased compensatory production of reticulocytes to replace the lost red blood cells.<ref name="Adamson"/>
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| Interpretation of these values are not standard and vary based on specific laboratory values and clinical context. </ref http://www.sysmex.ru/files/articles/Xtra_online_reticulocytes.pdf>
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| ==References== | |
| {{reflist}}
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| {{Myeloid blood tests}}
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| [[Category:Blood tests]]
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Jayson Berryhill is how I'm known as and my spouse doesn't like it at all. My working day occupation is a travel agent. My spouse and I reside in Kentucky. One of the things she enjoys most is canoeing and she's been performing it for quite a whilst.
Take a look at my blog post - free psychic reading