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Reticulocyte haemoglobin equivalent – RET-He

What is Ret-He – the Reticulocyte haemobolobin equivalent?

Measuring the haemoglobin content of reticulocytes, RET-He or reticulocyte haemoglobin equivalent, is a way of diagnosing and monitoring iron deficiency anaemia. Red blood cells have a 120-day lifetime. Therefore, detecting iron deficiencies and changes in the iron status of erythropoiesis is only possible relatively late using classical haematological parameters such as HGB, MCV, MCH, or by measuring hypochromic red blood cells (%Hypo-He).

Reticulocytes, the precursors of mature red blood cells, are swept into the blood stream from the bone marrow and usually mature over the course of around two days. Measuring the number of reticulocytes is therefore a quick measure of “quantity” in erythropoiesis in the marrow. Measuring the haemoglobin content of the reticulocytes means you can look at the current iron supply to erythropoiesis and judge the “quality” of the cells. This lets you detect changes in iron status far earlier than through the haemoglobin content of mature red blood cells.

Conventional biochemical markers for assessing the iron status, such as serum iron, transferrin or ferritin, are so drastically disturbed e.g. during inflammation in the course of an acute phase response but also in the presence of many other severe diseases that a clinical interpretation of the results is difficult or impossible.

So while low ferritin levels, for example, unequivocally indicate a lack of iron, normal or elevated levels do not let you draw any conclusions as to the bioavailability of the iron. In the presence of chronic diseases such as rheumatoid arthritis, but also in the presence of liver damage, tumours or chronic kidney disease, ferritin can also be elevated in the case of functional iron deficiency. In functional iron deficiency, iron stores can be filled, but the iron is not sufficiently released to the blood flow and therefore not bioavailable for the erythropoiesis. On the other hand, measuring the haemoglobin content of the reticulocytes as a direct assessment of the iron actually used for the biosynthesis of haemoglobin can indicate whether there is enough iron available for erythropoiesis even in these cases. It lets you take a snapshot of the “quality” of erythropoiesis and is an important tool for diagnosing and monitoring iron deficiency diseases.

Where should you use RET-He?

Anaemia is a common symptom of several diseases and one of the most underestimated red blood cell disorders. As a result, knowing a patient’s erythropoietic status can be essential. Many of our analysers offer the RET-He parameter – the reticulocyte haemoglobin equivalent. It is often used for patients with nephrological (kidney) disorders as they frequently suffer from anaemia in parallel. It is therefore especially important to include patients from the nephrology department or patients from dialysis centres and practices in analysis.

Ret-He is important for patients with anaemia of chronic disease (ACD). Any patient with a chronic inflammatory process, chronic infection or malignancy can develop ACD.

Patients with iron deficiency anaemia (IDA) will also benefit. IDA is widespread, underdiagnosed and can be found in a variety of patients. Some paediatric patients are vulnerable to developing IDA due to the growth phase.


The clinical usefulness of the Ret-He parameter has been proven and it is now an established parameter in advanced haematological analysis. “Reticulocyte haemoglobin content” is recommended in nephrology guidelines such as the European Best Practice Guidelines (EBPG), National Kidney Foundation Kidney Disease Outcome Quality Initiative (NKF KDOQI).


  • Indicates the trend of the current iron status.
  • RET-He and RET# together let clinicians draw conclusions on both the quality and quantity of the young RBC fraction.
  • Is an early marker for disease - earlier than clinical chemistry markers!
  • Fast and inexpensive!

Using RET-He

RET-He alone gives information on the current bioavailability of iron – a low value means iron is lacking or iron is not bioavailable for erythropoiesis. It is often used together with ferritin – a high or normal ferritin value together with a low RET-He value can suggest functional iron deficiency while low ferritin values together with low RET-He suggest a classic iron deficiency. Since ferritin is falsely increased during the acute phase of diseases, inflammation should be checked, e.g. by CRP.

The reference range for RET-He is approximately 28-35 pg [~1.77-2.22 fmol], below 28 pg [1.77 fmol] is considered iron deficient.

RET-He is used for monitoring erythropoietin (EPO) and/or IV iron therapy. If the value increases it indicates the therapy is having a positive effect.

Immature Granulocyte

Immature Platelet Fraction

Nucleated red blood cells

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