To determine which of the listed options is not a Red Blood Cell (RBC) index, it's important to understand what each term means in relation to RBC indices.
### RBC Indices:
1. Mean Cell Hemoglobin (MCH):
- This measures the average amount of hemoglobin per red blood cell.
- It's calculated by dividing the total hemoglobin by the number of red blood cells.
2. Mean Cell Volume (MCV):
- This measures the average volume of a red blood cell.
- It helps in classifying anemias as microcytic, normocytic, or macrocytic.
3. Mean Cell Size:
- This term is not typically used as a formal RBC index, but it could be considered synonymous with Mean Cell Volume (MCV), as MCV essentially measures the average size of the red blood cells.
4. Mean Cell Hemoglobin Colour:
- This term, however, is not an RBC index.
- RBC indices do not include a measurement or index termed "Mean Cell Hemoglobin Colour."
### Conclusion:
After examining the terms and their relations to RBC indices, the correct answer is:
D. Mean Cell Hemoglobin Colour
This response completes the detailed step-by-step explanation.
