A 28-year-old woman with iron deficiency anemia and a 30-year-old man with hereditary spherocytosis both present with microcytic anemia. Which laboratory parameter best distinguishes iron deficiency anemia from hemolytic anemia in this comparison?

Question

Accepted Answer

D. Low serum iron with elevated TIBC and low ferritin. ## Distinguishing IDA from Hemolytic Anemia ### Fundamental Pathophysiologic Difference **Key Point:** Iron deficiency anemia results from **depleted iron stores and impaired hemoglobin synthesis**, while hemolytic anemia results from **accelerated RBC destruction with intact iron metabolism**. These opposite pathophysiologies produce opposite iron metabolism patterns. ### Iron Metabolism Comparison Table | Parameter | Iron Deficiency Anemia | Hemolytic Anemia | | --- | --- | --- | | **Serum Iron** | Low (<60 μg/dL) | Normal or elevated | | **TIBC** | Elevated (>400 μg/dL) | Normal | | **Transferrin Saturation** | <16% | Normal (20–50%) | | **Serum Ferritin** | <15 ng/mL | Normal or elevated | | **Reticulocyte Count** | Low-normal or low | Elevated (>2%) | | **Indirect Bilirubin** | Normal | Elevated | | **LDH** | Normal | Elevated | | **Haptoglobin** | Normal | Low/absent | | **Marrow Iron Stores** | Absent | Normal or increased | ### Why Iron Metabolism Markers Discriminate **High-Yield:** Low serum iron + elevated TIBC + low ferritin is pathognomonic for IDA because: 1. Iron stores are depleted → ferritin is low 2. Body senses iron deficiency → TIBC increases (more transferrin produced) 3. Circulating iron is low → serum iron is low In hemolytic anemia, iron is released from destroyed RBCs and recycled, so iron metabolism remains normal despite high hemoglobin turnover. **Clinical Pearl:** The combination of low iron + elevated TIBC is rarely seen in any condition other than IDA. This pattern is more specific than individual parameters. ### Why Other Options Are Shared or Opposite ```mermaid flowchart TD A[Anemia] --> B{Mechanism?} B -->|Iron Deficiency| C["Low Fe, High TIBC
Low Ferritin"] B -->|Hemolysis| D["Normal Fe, Normal TIBC
High Reticulocytes
High Bilirubin"] C --> E["IDA: Iron metabolism abnormal"] D --> F["Hemolytic: RBC destruction abnormal"] ``` - **Reticulocyte count & bilirubin:** Elevated in hemolytic anemia, but low-normal in IDA. These reflect RBC destruction, not iron status. - **LDH & haptoglobin:** Elevated LDH and low haptoglobin are hemolysis markers, not iron deficiency markers. - **DAT/Coombs:** Negative in both IDA and hereditary spherocytosis (HS is intrinsic RBC defect, not immune hemolysis). [cite:Robbins 10e Ch 14; Harrison 21e Ch 99]

Answer

A. Reticulocyte count >2% with elevated indirect bilirubin

Answer

B. Elevated LDH with low haptoglobin

Answer

C. Negative direct antiglobulin test (DAT/Coombs)

A 28-year-old woman with iron deficiency anemia and a 30-year-old man with hereditary spherocytosis both present with microcytic anemia. Which laboratory parameter best distinguishes iron deficiency anemia from hemolytic anemia in this comparison?

Explanation

Distinguishing IDA from Hemolytic Anemia

Fundamental Pathophysiologic Difference

Iron Metabolism Comparison Table

Why Iron Metabolism Markers Discriminate

Why Other Options Are Shared or Opposite

Practice similar questions

Join our NEET PG community

Parameter	Iron Deficiency Anemia	Hemolytic Anemia
Serum Iron	Low (<60 μg/dL)	Normal or elevated
TIBC	Elevated (>400 μg/dL)	Normal
Transferrin Saturation	<16%	Normal (20–50%)
Serum Ferritin	<15 ng/mL	Normal or elevated
Reticulocyte Count	Low-normal or low	Elevated (>2%)
Indirect Bilirubin	Normal	Elevated
LDH	Normal	Elevated
Haptoglobin	Normal	Low/absent
Marrow Iron Stores	Absent	Normal or increased