Green and King Index Calculator
Calculate the Green and King Index using hemoglobin, mean corpuscular volume and red blood cell count to help distinguish an iron deficiency pattern from a thalassemia trait pattern in microcytic anemia.
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What is the Green and King Index?
The Green and King Index is a red blood cell discrimination index developed to help differentiate iron deficiency anemia from thalassemia trait in patients with microcytic anemia.
It combines hemoglobin concentration, mean corpuscular volume and red blood cell count. The calculation is particularly useful as a screening approach when microcytosis is present.
Lower index values tend to favor a thalassemia trait pattern, while higher values tend to favor an iron deficiency pattern. However, overlap between the two conditions can occur.
Green and King Index Interpretation
| Index Pattern | Screening Pattern | Clinical Consideration |
|---|---|---|
| Lower values | Thalassemia trait pattern | Consider thalassemia trait when supported by the CBC, clinical background and other laboratory findings. |
| Intermediate values | Borderline or indeterminate | The index may not reliably distinguish the underlying cause. Additional laboratory evaluation is appropriate. |
| Higher values | Iron deficiency pattern | Consider iron deficiency, particularly when ferritin and iron studies support iron depletion. |
Cutoffs and diagnostic performance can vary between studies and patient populations. The Green and King Index should be regarded as a screening or discrimination tool rather than a definitive diagnostic test.
Green and King Index Compared With Other Indices
| Index | Main Parameters | Typical Use |
|---|---|---|
| Mentzer Index | MCV / RBC | Screening for thalassemia trait versus iron deficiency |
| Green and King Index | Hb, MCV and RBC | Microcytic anemia discrimination |
| Shine and Lal Index | MCV and MCH | Screening for thalassemia trait |
| Srivastava Index | MCH / RBC | Thalassemia trait versus iron deficiency screening |
| RDW Index | MCV, RBC and RDW | Microcytosis discrimination |
What Should Be Considered After an Abnormal Index?
A discrimination index can help identify patients who may require further evaluation, but it does not establish the underlying diagnosis.
When iron deficiency is suspected, ferritin, serum iron, transferrin saturation and other iron studies should be interpreted together with the clinical context.
When thalassemia is suspected, hemoglobin analysis may be useful. Hemoglobin electrophoresis or HPLC can help identify abnormalities such as elevated HbA2 in beta-thalassemia trait.
Alpha-thalassemia trait may have a normal hemoglobin analysis and may require molecular testing when clinical suspicion remains high.
Green and King Index Calculator - Frequently Asked Questions
What is the Green and King Index formula?
The Green and King Index is calculated using hemoglobin, MCV and RBC count. The formula used here is Hb multiplied by MCV and divided by the RBC count.
What does a low Green and King Index suggest?
Lower values generally favor a thalassemia trait pattern, particularly when marked microcytosis occurs with a relatively preserved RBC count.
What does a high Green and King Index suggest?
Higher values tend to favor an iron deficiency pattern, although the result should be correlated with ferritin and other iron studies.
Can the Green and King Index diagnose thalassemia?
No. It is a screening and discrimination index. Definitive evaluation may require hemoglobin analysis and, in selected cases, molecular testing.
Why are hemoglobin, MCV and RBC used?
These parameters describe important features of microcytic anemia and can help identify patterns that differ between iron deficiency and thalassemia trait.
Should ferritin be checked?
Yes. Ferritin is an important laboratory test when iron deficiency is suspected, although inflammation and other conditions can affect ferritin interpretation.
Medical Disclaimer: This calculator is intended for educational and clinical reference purposes. The Green and King Index is a screening and discrimination index and should not be used as a standalone diagnostic test for iron deficiency or thalassemia. Interpretation should consider the complete CBC, peripheral smear, ferritin, iron studies, clinical history and, when appropriate, hemoglobin analysis or molecular testing. Reference thresholds and diagnostic performance may vary among populations and clinical settings.
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