Mean Cell Hemoglobin Value Can Be Useful

The perspective of Drs. W. Richard Burack, Ronald S. Go, and Marshall A. Lichtman¹  certainly will generate discussion, but it hopefully won’t lead to what they call “meaningful changes” for patients and institutions. I believe many of their proposed changes to the complete blood count (CBC) will have the greatest impact on physicians — and will be negative. I know two of the authors quite well, and while I have tremendous regard for their knowledge, I don’t agree with these proposed changes.

They nicely describe the long history of the CBC, which alone enables one to recognize how generations of physicians are familiar and comfortable with the current format. Changing that adds yet another hassle to the practice of medicine, as we would need to adjust to format changes that I don’t believe will help with time management.

Whereas it is true that it is time-consuming to answer patient questions in the portal about an abnormal mean corpuscular hemoglobin, changing the CBC may not diminish messages, as we will still receive questions about many other labs such as the chloride, anion gap, and glomerular filtration rate. Many physicians believe patient portals are poorly designed, but responding to that by changing what data we see is ill-advised. Perhaps the electronic medical record (EMR) should just release the abbreviated CBC to the patient but let their physician see all the data. Better yet, let the clinician decide which data points we want with a formatting menu. This should be feasible with an EMR.

There is ample literature about how the EMR makes many clinical tasks more difficult. Some of these proposed changes would add to that as well. For example, the polycythemia vera (PV) order sets in the EMR use hematocrit (HCT) values for the phlebotomy threshold. This is based on clinical trial data and the old PV study group reports from years ago. All of those order sets would need to be redone, which, quite frankly, is more of a hassle than answering patient messages. I personally have approximately 50 patients who would be affected by that change alone, and the burden of making those order changes is significant. In a similar manner, order sets for erythropoiesis-stimulating agents use both hemoglobin and HCT values. Changes would need to be made in those order sets as well, but, notably, Medicare would first need to change its policy, as it mandates both values be assessed for coverage. Changing Medicare guidelines may be the biggest challenge.

The example of thalassemia is an interesting one, as some of the proposed approaches are much more cumbersome than looking at the red blood cell (RBC) number and mean corpuscular volume. I am not sure if it is a national policy, but in New York state, you need a signed consent from the patient before performing a hemoglobin electrophoresis. In addition, this would only be useful for beta-thalassemia — not alpha-thalassemia. Looking at the blood smear for basophilic stippling is a great goal but is not always practical based on the logistics of clinical practice. I have also seen many patients with both iron deficiency and thalassemia trait, and having access to the RBC number from years earlier often helps diagnose that combination, as the old RBC numbers are typically increased and diminish as the patient’s iron stores become depleted.

I understand the desire to remove the white blood cell (WBC) differential percentages, but that too would negatively impact my practice, as I have a longstanding routine of looking at lab data with both relative as well as absolute values. That is how my mind has processed lab results for more than 40 years. I like doing the math, and I don’t see the harm in providing both values. The “left shift” recognized by generations of physicians would need to be redefined (and retaught) with absolute values. I recognize and agree that the absolute values are clinically critical, but on a practical level, some important clinical changes may be missed by those unfamiliar with the new reporting structure. Although the authors don’t agree with the approach of some surgeons, they have relied on the neutrophil percentage for decades, and abruptly changing lab reports may hurt some patients. Lastly, completely removing the total WBC in the proposed CBC with differential report is so bizarre to me that I have no further comment.

In summary, I strongly disagree with many aspects of the authors’ proposals and hope other clinicians speak up so that we have a role in determining how we see lab data as we continue to practice clinical medicine.

–Ronald L. Sham, MD, Hematology Division, Rochester General Hospital, Rochester, NY

Authors’ Reply: Dr. Sham makes several good points related to hematologic considerations. Few are pathophysiologically relevant, but they are embedded in administrative dicta or longstanding habits of practice. Hemoglobin, hematocrit, and red cell count are redundant for the overwhelming fraction of CBCs. Change of a procedure that is 90 years old is difficult. It is particularly so for hematologists. The overwhelming number of the tens of millions of CBCs performed annually are not for hematologic diagnosis. When they are performed in patients with hematologic problems, many are repetitive exams (e.g., to follow the response to treatment or periodic surveillance for those in remission).

Logic dictates that the percent of specific leukocyte subtypes is irrelevant, despite its use by many physicians. The white cell count is useful for screening but is not a physiological variable. Each white cell type has its own regulatory controls; it is the absolute count of each that is the relevant variable. Surgeons and others should use the absolute white cell counts in making medical decisions. The full CBC we propose is appropriate for evaluation of the new acutely or chronically ill patient or those with a hematologic problem. The requirement for a reticulocyte count and an evaluation of the blood smear are both important additions. We add the caveat that physicians can add other variables in the uncommon circumstances in which they are required. An analysis of the usefulness of multiple different indices for the differentiation of iron deficiency and thalassemia minor finds them of low specificity and sensitivity.¹ 

Dr. Ruiz-Argüelles makes an interesting point regarding the MCH, but it is not one most physicians will appreciate. We hope institutions will consider some of our suggestions to make this important test more impactful and — where appropriate — more concise. Surveys indicate that physicians use only a few variables from the CBC in their practice, and values such as the MCH and MCHC are not among them.² 

–Marshall A. Lichtman, MD, Ronald S. Go, MD, and W. Richard Burack, MD, PhD