What is Rtc(B)-MCH?
Rtc(B)-MCH—also known as reticulocyte hemoglobin—measures the average hemoglobin content in reticulocytes. Reticulocytes are newly formed red blood cells that have recently left the bone marrow and will soon develop into mature red blood cells. Hemoglobin is the protein within red blood cells that binds and transports oxygen. For the bone marrow to produce hemoglobin, an adequate supply of iron, among other things, is required. Because reticulocytes are newly formed, their hemoglobin content provides information on the amount of iron recently available for red blood cell production.
What does Rtc(B)-MCH indicate?
Rtc(B)-MCH reflects iron availability for active blood cell formation, or erythropoiesis. A low value indicates that newly formed red blood cells contain less hemoglobin than expected, suggesting that the bone marrow lacked sufficient iron for normal hemoglobin production. This makes the marker useful for assessing iron deficiency and so-called iron-restricted or functional iron deficiency—conditions where the body's iron stores are not necessarily depleted, yet insufficient iron is available for blood cell formation.
Why is Rtc(B)-MCH analyzed?
The test is primarily used as a supplementary tool in the investigation and monitoring of iron deficiency and anemia.
Since reticulocytes represent the most recent production of red blood cells, Rtc(B)-MCH can provide a relatively current picture of whether the bone marrow has access to the iron needed for hemoglobin synthesis.Rtc(B)-MCH can be relevant in cases such as:
- suspected iron deficiency or iron deficiency anemia.
- investigation of anemia.
- assessment of functional iron deficiency.
- chronic inflammation or chronic disease, where standard iron markers may be more difficult to interpret.
- kidney disease and dialysis treatment.
- monitoring of iron therapy.
Rtc(B)-MCH in iron deficiency
Iron is essential for hemoglobin formation. Consequently, when the supply of iron to the bone marrow decreases, new red blood cells may have a lower hemoglobin content. A low Rtc(B)-MCH value can thus indicate that the iron supply for erythropoiesis is insufficient. This marker differs from, for example, ferritin, which is primarily used to assess the body's iron stores. Furthermore, ferritin levels can rise due to inflammation and other medical conditions. Instead, Rtc(B)-MCH provides information on the amount of iron actually available for hemoglobin formation in the most recently produced red blood cells.
What is the difference between Rtc(B)-MCH and MCH?
MCH describes the average amount of hemoglobin in mature red blood cells. Since red blood cells circulate for a long time, MCH reflects changes in blood cell formation over an extended period. Rtc(B)-MCH instead measures the hemoglobin content of newly formed reticulocytes. Therefore, Rtc(B)-MCH can provide more up-to-date information regarding iron availability to the bone marrow and ongoing red blood cell production.
Rtc(B)-MCH during iron treatment
Rtc(B)-MCH can also be used to monitor the effect of iron treatment. As iron availability to the bone marrow improves, the hemoglobin content in newly formed reticulocytes may increase. A change in Rtc(B)-MCH can therefore provide information on how blood cell formation is responding to the treatment.
How is Rtc(B)-MCH interpreted?
A low Rtc(B)-MCH value may indicate insufficient iron availability for blood cell formation. This can occur in cases of classic iron deficiency but also in functional iron deficiency, such as in association with inflammation or chronic disease. A value within the laboratory's reference range generally indicates that newly formed red blood cells have had sufficient access to iron for hemoglobin production. However, a normal value does not rule out all causes of anemia. Therefore, Rtc(B)-MCH should not be interpreted in isolation. Assessment is usually made in conjunction with other analyses—such as hemoglobin (Hb), ferritin, transferrin saturation, MCV, MCH, and reticulocyte counts—and based on the individual's clinical situation.
Reference ranges and low Rtc(B)-MCH values
Rtc(B)-MCH is typically expressed in picograms (pg). Reference ranges may vary between laboratories and analytical methods; therefore, test results should always be evaluated against the reference range specified by the analyzing laboratory. Low values are a sensitive indicator of iron deficiency and may suggest that the iron supply for ongoing erythropoiesis is insufficient.
Rtc(B)-MCH has primarily been studied in dialysis patients. For patients undergoing hemodialysis, a threshold of approximately <29 pg is often used to assist in assessing functional iron deficiency. However, this threshold should not be regarded as a general reference range for all patient groups.
