Tracking MCH in Evaluating Early Iron Deficiency

MCH less than 28 pg May be a “Red Flag” for Iron Deficiency

Iron deficiency is important to understand as it may impact hair growth. Although the role of iron deficiency is generally overstated by most clinicians when evaluating hair loss, it is still an extremely important and relevant topic.

Iron deficiency can occur with or without a low hemoglobin level. In other words, iron deficiency can occur with or without the patient having an anemia. Iron deficiency without anemia is referred to as IDWA and iron deficiency with anemia is referred to as IDA.

Iron deficiency without anemia can not only affect hair but can affect other health issues. Some studies have suggested that IDWA can affect cognition in adolescent females and cause fatigue in adult women. The risk of iron deficiency is increased in women, pregnancy, obesity, black women, and vegatarian diets. Iron deficiency in those over 60 must also raise suspicion for malignancy and shoudl prompt further evaluation by the clinician.

The gold standard for assessing iron deficiency is to sample the bone marrow and use an iron stain to see how much iron is actually there. This is impractical - and painful. Fortunately, several blood tests help give us an estimate of the iron status of our patients.

There are many definitions of iron deficiency and this is very inconsistent. Some choose ferritin levels less than 30, some chose transferrin saturation less than 16-20 and some chose serum iron less than 13 umol.L. Other blood parameters like MCV and RDW are helpful but less sensitive. It is often said that provided the transferrin saturation remains above 16-20% there is sufficient iron to make blood and keep the blood parameters fairly normal. A transferrin saturation less than 16 % indicates that the iron supply has reduced to a point where normal red blood cell production is going to be impaired. There is a current consenus among hematologists that a ferritin cut of of 30 is fairly reliable to detect iron deficiency in most patients. There is debate amongst hair doctors as to whether this cut off is truly the right cut off for hair issues. It’s a bit of a stretch to suggest higher cut offs are really needed but many still do stretch.

Ferritin levels are helpful but tricky to interpret because ferritin levels can rise in inflammatory states. Because of this, we refer to ferritin as an acute phase reactant. One must be careful to use ferritin levels as an estimate for iron status in patients with inflammatory conditions. The cut off to use if inflammation is suspected is not clear and may different for different types of inflammation. Elevated CRP is one of the more reliable tests to detect inflammation but it too is not perfect by any means.

In non inflammatory states, a ferritin less than 24 increases the risk that a person truly has iron deficiency and a level less than 15 dramatically increases the risk. A transferrin saturation less than 10 dramatically increases the risk of iron deficiency but the cut off of 20 is helpful to capture the many who are also in the group 10-20. An serum iron less than 13 umol/L increases the risk as well.

In inflammatory states, a ferritin of less than 100 with a transferrin saturation less than 20 may be suggestive or iron deficiency. Again, it depends on the actual inflammatory state.

The author of a new study highlights that falling levels of mean corpuscular haemoglobin (MCH) or falling levels of mean corpuscular haemoglobin concentration (MCHC) could be the very very early sign of iron deficiency without anaemia (IDWA) and changes much sooner than MCV values. The author reported 219 female athletes aged 15–20 years. During the progression from the status of normal iron stores (defined as serum ferritin ≥30 μg/L) to iron deficient status (defined as serum ferritin <30 μg/L) the fall in MCH and MCHC happened much sooner than any reduction in mean corpuscular volume (MCV). Also among subjects who had progressed to iron deficiency, the mean value for haemoglobin (Hb) was 132.7 g/L vs 139.2 g/L in the iron replete subgroup.

In another study of 770 subjects with IDWA, there were 463 (60.1 %) who had MCH amounting to ≤28 pg vs 209 27.1 % with MCV of ≤80 fL.

Overall, the authors conclude that MCH of less than 28 pg is more prevalent than MCV of ≤80 fL in IDWA subjects, an MCH value of <28 pg should be a “red flag” for IDWA and prompt the clinician to either undertake further investigation or encourage steps to prevent further reduction.

Conclusion

I liked this study. It’s important to follow iron parameters in patients with hair loss. It’s clear that patients with ferritin less than 15 are at high risk for hair loss issues from low iron. it’s more challenging to know how to manage patients with ferritin 15-40. Generally speaking we advise patients with ferritin less than 40 to take iron. We know that some of these patients will get some benefit from taking iron but a very large proportion will be taking pills and spending money for not benefit at all.

The challenge comes with following patients who have had iron deficiency in the past. We may order serum ferritin labs in the future as well as all the other parameters like hemoglobin, MCV, MCH, RDW ,serum, iron, TIBC, transferrin saturation. Sometimes we order CRP +/- ESR to get a sense of inflammation although we know this is not so reliable. All of these labs need to be interpreted in context.

But a patient with MCH less than 28 may clue us that iron deficiency is indeed possible. A falling ferritin, and falling transferrin saturation may provide us with valuable clues as well and these may happen far ahead of any change in MCV and RDW.

REFERENCE

Jolobe et al. The index of suspicion for iron deficiency in non-anaemic subjects. Clin Med (Lond) . 2021 Jul;21(4):e428-e429.