Immature reticulocytes and haemoglobin content — RET-y (CHr)

Laboratory parameters for managing erythropoietin therapy in chronic dialysis patients

In addition to the proven parameters for assessing the iron status of patients, such as ferritin and transferrin saturation, several new „red blood count” fractions have been discussed in recent years. All of these tests have only now become possible because of the far-reaching technical improvements in analytical equipment – scattered laser light analysis and fluorescence cytometry.

One of these parameters measures hypochromic erythrocytes, which have already been described in several publications and guidelines. The big disadvantage of these cells is their relatively long survival time in the blood (up to 90 days), so that there is no current and immediate effect after EPO therapy. The immature reticulocytes (CHr / RET-y) respond much more quickly. They can be used for the differential diagnosis of unclear normochromic (incipient hypochromic) anaemia and for distinguishing actual iron deficiency from functional iron deficiency (faulty iron supply mechanism).

RET-y values below 1710 with a concomitant increase in CrP and a normal soluble transferrin receptor are the only indication of the onset of iron deficiency.
When monitoring patients after EPO therapy and/or intravenous iron administration, the immature reticulocyte fraction (IRF) reflects the stimulation of the bone marrow cells. However, an increased IRF value with a simultaneous RET-y reduction (< 1710) also means that there is no iron supply and that EPO therapy might not be of use.

Further possible applications of these laboratory parameters include the monitoring of antibody therapy in tumours or blocking cytokines in autoimmune diseases.

Test material
EDTA blood

Reference Ranges3 - 18 years Adults
Male Female
IRF %:4 - 6 1,5 - 13,7 1,1 - 15,9
(Median 19)(Median 5.7)(Median 5.7)
RET-y: Not yet determined1710 - 19631710 - 1963
(Median 1844)(Median 1844)
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