It starts in medical school, regularly appears in your medical training, sneaks around nursing schools and is an impetus for discussions in the ICU: The great myths about Hemoglobin (Hb) and Hematocrit (Hct).
These two haematological lab-parameters are part of our daily life at work and are mostly measured together... as a package. Some clinicians look at haemoglobin levels, others prefer hematocrit levels... but then there is always someone making a great deal of differentiating between the two parameters and making all sort of diagnostic conclusions. 'Hct is better to determine dilution of the patient' or 'Acute blood loss is better determined by Hb than Hct'... and so on.
So here's the question: What actually is the difference between Hb and Hct? Do we need to measure both in clinical practice?
What's the difference?
Hemoglobin levels are mostly measured by automated machines designed to perform different tests in blood. Within the machine, the red blood cells are broken down to get the haemoglobin into a solution. The concentration of haemoglobin is then measured by spectrophotometry using the methemoglobin cyanide method.
Hematocrit levels in contrast are actually calculated by an automated analyzer... It is actually not measured directly! The analyser multiplies the red blood cell count by their mean corpuscular volume.
What is Fact?
There simply is NO difference between Hemoglobin and Hematocrit by means of clinical information!
Once and for all!
Nijboer J et al. J Trauma. 2007;62(5):1310-2.