Erythrocyte indices
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Also commonly called red blood cell indices or RBC indices, the erythrocyte indices are a set of clinically useful parameters calculated from measurements of erythrocytes. These are commonly reported as part of a complete blood count.
Basic indices
These are computed from the three basic measurements on erythrocytes:
- Hemoglobin (Hgb), in grams per 100ml
- Hematocrit (Hct), a percentage
- Red blood cell count (RBC), millions per cubic micrometer
Mean corpuscular volume
Usually called MCV, this is the average volume enclosed by a red cell, calculated as:
MCV = 10 x (Hematocrit / Red Blood Cell Count)
It is especially useful in the differential diagnosis of anemia. The basic classification of MCV, using approximate values, is:
- <80: Microcytic
- 80-100: Normocytic
- >100: Macrocytic
Exact cutoffs for each range vary with the patient's age and sex, and both laboratory method and expert opinion. For example, a number of hematologists use < 78 as the beginning of the microcytic range.
Mean corpuscular hemoglobin
MCH = (Hgb * 10)/RBC
Mean corpuscular hemoglobin concentration
MCHC = (Hgb * 100) / Hct
Classification:
- Hypochromic: < 32
- Normochromic: 32-36
- Hyperchromic: > 36
Additional derivations
Mentzer index
Mentzer Index = MCV / RBC Count
- Ratio <13: Thalassemia
- Ratio >13: Iron deficiency anemia, Hemoglobinopathy