What is the Mentzer index (Mean Corpuscular Volume to Red Cell Distribution Width ratio)?

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From the Guidelines

The Mentzer index is a calculation used to differentiate between iron deficiency anemia and beta-thalassemia trait, and it is calculated by dividing the Mean Corpuscular Volume (MCV) by the Red Cell Distribution Width (RDW) [ 1 ].

Key Components of the Mentzer Index

  • MCV: a measure of the average size of red blood cells
  • RDW: a measure of the variation in red blood cell size, calculated as {SD of red blood cell volume (fL)/MCV (fL)} x 100 [ 1 ]

Interpretation of the Mentzer Index

The Mentzer index is used as a preliminary screening tool to differentiate between iron deficiency anemia and beta-thalassemia trait [ 1 ].

  • A low MCV and an RDW of greater than 14.0% indicates iron-deficiency anemia
  • A low MCV and an RDW less than or equal to 14.0% indicates thalassemia minor However, the provided evidence does not give a clear definition of the Mentzer index as a ratio of MCV to RDW. Further testing, such as hemoglobin electrophoresis or genetic testing, should be performed to confirm the diagnosis [ 1 ].

From the Research

Definition of Mentzer Index

  • The Mentzer index is a calculated value used to differentiate between beta-thalassemia trait and iron-deficiency anemia 2, 3, 4, 5, 6.
  • It is calculated as the ratio of Mean Corpuscular Volume (MCV) to Red Cell Distribution Width (RDW) 2, 3, 4, 5, 6.

Calculation and Interpretation

  • The Mentzer index is calculated using the formula: MCV/RDW 2, 3, 4, 5, 6.
  • A value of less than 12-13 is often used to indicate beta-thalassemia trait, while a value greater than 13 is indicative of iron-deficiency anemia 2, 3, 4, 5, 6.

Diagnostic Accuracy

  • The Mentzer index has been shown to have high diagnostic accuracy in differentiating between beta-thalassemia trait and iron-deficiency anemia, with sensitivity and specificity values ranging from 90-95% 3, 4, 5, 6.
  • However, the accuracy of the Mentzer index can vary depending on the population being studied and the cutoff values used 3, 4, 5, 6.

Comparison with Other Indices

  • The Mentzer index has been compared to other discrimination indices, such as the CRUISE index, Srivastava index, and Green and King index, and has been shown to have similar or superior diagnostic accuracy 3, 5, 6.
  • The choice of index may depend on the specific population being studied and the availability of laboratory tests 3, 5, 6.

References

1
Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

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Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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