Test Code: Retic Preferred Name Reticulocytes

45 minutes
As required
1 hour
Medicare Item

Test Tubes

ImageSpecimen TypeSpecimen VolumeTube Type
Blood (adult)3 mLEDTA 3 mL whole blood (Lavender top)
Blood (neonate)500µLEDTA 500 uL Microtainer (Lavender Top)


If collecting for FBC also, there is no need for an additional EDTA tube to be collected provided the supplied EDTA tube is filled.


Enhanced red cell production is indicated by an increase in circulating reticulocytes. A reticulocyte production index (RPI) is calculated from haematologic data: the calculation converts the RETICULOCYTE COUNT, expressed as a percentage, to an INDEX reflecting the production rate, expressed as a multiple of normal. Two corrections are incorporated into the calculation, one for the degree of anaemia and another for early release of reticulocytes from the marrow ("shift reticulocytes"). Because these "shift reticulocytes" are released at an earlier stage of their development, they survive as reticulocytes for a longer time in the circulation. The correction for anaemia is made by multiplying the reticulocyte % by a ratio of the patient's haematocrit to an average normal value. The correction for shift incorporates a value for the reticulocyte maturation time. RPI = retic %/retic maturation time* (days) x Patient's haematocrit/0.45. The average normal RPI is 1, but in the presence of anaemia, an increase is to be expected. If RPI > 3, production is assumed to be increased (haemolytic anaemia). At RPIs  < 2, a defect in production is assumed (hypoproliferative OR ineffective erythropoiesis). [* Maturation time: 1 day if haematocrit 0.35-0.45; 1.5 days if Hct 0.25-0.35; 2 days if Hct 0.15-0.25; 2.5 days if Hct > 0.15]

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