Srivastava Index Calculator
Calculate the Srivastava Index from mean corpuscular hemoglobin (MCH) and red blood cell (RBC) count to help differentiate an iron deficiency pattern from a thalassemia trait pattern.
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What is the Srivastava Index?
The Srivastava Index is a red blood cell discrimination index that uses the mean corpuscular hemoglobin (MCH) and RBC count to help distinguish an iron deficiency pattern from a possible thalassemia trait pattern.
It is primarily intended as a screening tool in patients with microcytosis or suspected microcytic anemia.
A lower Srivastava Index is traditionally associated with a thalassemia trait pattern, while a higher value is more consistent with an iron deficiency pattern.
Srivastava Index Interpretation
| Srivastava Index | Screening Pattern | Clinical Consideration |
|---|---|---|
| Less than 3.8 | Thalassemia trait pattern | Consider thalassemia trait in the appropriate clinical and hematological setting. |
| Around 3.8 | Borderline / indeterminate | The index alone may not reliably distinguish the underlying cause. |
| 3.8 or higher | Iron deficiency pattern | Iron deficiency should be considered, particularly when ferritin and other iron studies support the finding. |
The commonly used threshold of 3.8 is a screening convention. Diagnostic performance can vary between populations and clinical settings.
Srivastava Index and Other Microcytic Indices
| Index | Formula | Common Interpretation |
|---|---|---|
| Srivastava Index | MCH / RBC | Lower values favor thalassemia trait pattern |
| Mentzer Index | MCV / RBC | Less than 13 traditionally favors thalassemia trait |
| Shine and Lal Index | MCV squared x MCH / 100 | Lower values may favor thalassemia trait |
| RDW Index | MCV x RDW / RBC | Used as an additional discrimination index |
What Should Be Considered After a Low Srivastava Index?
A low Srivastava Index may support a thalassemia trait pattern, but it does not establish the diagnosis.
Evaluation should include the complete CBC and, when appropriate, ferritin, serum iron, transferrin saturation, peripheral blood smear and hemoglobin analysis.
Hemoglobin electrophoresis or other hemoglobin analysis may help identify beta-thalassemia trait and some other hemoglobin disorders.
A normal hemoglobin analysis does not completely exclude alpha-thalassemia trait. Molecular testing may be considered in selected clinical situations.
Srivastava Index Calculator - Frequently Asked Questions
What is the Srivastava Index formula?
The Srivastava Index is calculated by dividing the MCH in pg by the RBC count expressed in x10^12/L.
What does a low Srivastava Index indicate?
A lower value is traditionally associated with a thalassemia trait pattern, particularly in patients with microcytosis.
What cutoff is commonly used?
A commonly cited cutoff is approximately 3.8, with lower values traditionally favoring thalassemia trait and higher values favoring iron deficiency.
Can the Srivastava Index diagnose thalassemia?
No. It is a screening or discrimination index. Definitive evaluation may require hemoglobin analysis, iron studies and, in selected cases, molecular testing.
Why is the RBC count important?
Thalassemia trait can produce microcytosis with a relatively preserved or increased RBC count, whereas iron deficiency often produces a lower RBC count.
Should ferritin be checked?
Yes. Ferritin and other iron studies provide more direct evidence when evaluating possible iron deficiency than a discrimination index alone.
Medical Disclaimer: This calculator is intended for educational and clinical reference purposes. The Srivastava 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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