A 34-year-old woman with membranous nephropathy has had nephrotic-range proteinuria of about 9 g/day for 8 months and now reports fatigue. Results: hemoglobin 10.1 g/dL [101 g/L], MCV 74 fL, albumin 1.9 g/dL [19 g/L], CRP 2 mg/L (reference < 5), serum iron 30 µg/dL [5.4 µmol/L] (reference 60-170 µg/dL [10.7-30.4 µmol/L]), UIBC 130 µg/dL [23.3 µmol/L] and ferritin 9 ng/mL [9 µg/L] (reference 15-150). Reference intervals: TIBC 250-425 µg/dL [44.8-76.1 µmol/L]; saturation 20-50%. Which saturation and interpretation are correct?

19%; iron deficiency despite a low TIBC

81%; iron overload with low transferrin

19%; anemia of chronic inflammation

23%; iron deficiency despite a low TIBC

A 48-year-old man with fatigue, joint pain and a raised ALT has serum iron 210 µg/dL (37.6 µmol/L), TIBC 250 µg/dL (44.8 µmol/L) and ferritin 1,450 ng/mL (1,450 µg/L). His transferrin saturation and its meaning are:

16%, suggesting iron deficiency

119%, suggesting a sample error

84%, within the reference range

In most serum iron methods, iron is freed from transferrin at acid pH and then reduced before ferrozine is added. Why is the reduction step needed?

The chromogen binds ferrous (Fe2+) iron

Reduction prevents copper interference

Reduction frees iron stored in ferritin

The chromogen binds ferric (Fe3+) iron

Iron, TIBC and trace elements

10 ASCP MLS practice questions on Iron, TIBC and trace elements, part of Chemistry. The first 10 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

Question 1 · Hard
A 34-year-old woman with membranous nephropathy has had nephrotic-range proteinuria of about 9 g/day for 8 months and now reports fatigue. Results: hemoglobin 10.1 g/dL [101 g/L], MCV 74 fL, albumin 1.9 g/dL [19 g/L], CRP 2 mg/L (reference < 5), serum iron 30 µg/dL [5.4 µmol/L] (reference 60-170 µg/dL [10.7-30.4 µmol/L]), UIBC 130 µg/dL [23.3 µmol/L] and ferritin 9 ng/mL [9 µg/L] (reference 15-150). Reference intervals: TIBC 250-425 µg/dL [44.8-76.1 µmol/L]; saturation 20-50%. Which saturation and interpretation are correct?
1. A81%; iron overload with low transferrin
2. B19%; iron deficiency despite a low TIBC
3. C19%; anemia of chronic inflammation
4. D23%; iron deficiency despite a low TIBC
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Answer: B · 19%; iron deficiency despite a low TIBC
TIBC is iron plus UIBC, 30 + 130 = 160 µg/dL, so the saturation is 30 / 160 = 19%. A low TIBC usually points to anemia of inflammation, but in nephrotic syndrome transferrin is lost in the urine with other mid-sized proteins, so TIBC falls whatever the iron status. A ferritin of 9 ng/mL with a normal CRP shows that iron stores are empty, and the microcytic anemia fits iron deficiency, partly from urinary loss of transferrin-bound iron. Dividing iron by UIBC gives 23%, and dividing UIBC by TIBC gives 81%, which is the unsaturated fraction rather than the saturation. In protein-losing states, ferritin is a better guide to iron stores than TIBC.
- A: 81% is the unsaturated fraction (UIBC/TIBC), not the saturation.
- C: A ferritin of 9 ng/mL with a normal CRP shows absent iron stores, not inflammation.
- D: 23% divides iron by UIBC; saturation divides iron by TIBC.
Question 2 · Hard
A UIBC assay adds 500 µg/dL of iron to serum, and 150 µg/dL is left unbound after transferrin takes up what it can. Serum iron is 60 µg/dL (10.7 µmol/L). The TIBC is:
1. A410 µg/dL (73.4 µmol/L)
2. B210 µg/dL (37.6 µmol/L)
3. C290 µg/dL (51.9 µmol/L)
4. D350 µg/dL (62.7 µmol/L)
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Answer: A · 410 µg/dL (73.4 µmol/L)
UIBC = iron added - iron left unbound = 500 - 150 = 350 µg/dL. TIBC = serum iron + UIBC = 60 + 350 = 410 µg/dL. The saturation is 60 ÷ 410 × 100, about 15%. UIBC methods measure the excess unbound iron with a chromogen, so the free binding capacity is found by difference.
- B: 210 treats the iron left unbound as if it were the UIBC.
- C: 290 subtracts the serum iron instead of adding it.
- D: 350 is the UIBC; the patient's own iron must be added to get TIBC.
Question 3 · Hard
A 48-year-old man with fatigue, joint pain and a raised ALT has serum iron 210 µg/dL (37.6 µmol/L), TIBC 250 µg/dL (44.8 µmol/L) and ferritin 1,450 ng/mL (1,450 µg/L). His transferrin saturation and its meaning are:
1. A16%, suggesting iron deficiency
2. B84%, suggesting iron overload
3. C119%, suggesting a sample error
4. D84%, within the reference range
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Answer: B · 84%, suggesting iron overload
Saturation = 210 ÷ 250 × 100 = 84%. A fasting saturation above 45% is the usual cutoff for investigating hereditary hemochromatosis, and the very high ferritin shows heavy iron stores. The next step is HFE genotyping for the C282Y variant. Liver injury and joint pain are typical effects of iron deposition.
- A: 16% is the UIBC share, (250 - 210) ÷ 250, not the saturation.
- C: 119% comes from dividing TIBC by iron, the inverted ratio.
- D: The usual saturation range is about 20-50%, so 84% is high.
Question 4 · Medium
In most serum iron methods, iron is freed from transferrin at acid pH and then reduced before ferrozine is added. Why is the reduction step needed?
1. AReduction prevents copper interference
2. BReduction frees iron stored in ferritin
3. CThe chromogen binds ferrous (Fe2+) iron
4. DThe chromogen binds ferric (Fe3+) iron
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Answer: C · The chromogen binds ferrous (Fe2+) iron
Iron travels on transferrin as ferric (Fe3+) iron. Acid releases it, and a reducing agent such as ascorbate converts it to ferrous (Fe2+) iron, which forms a colored complex with chromogens such as ferrozine or ferene. Copper can also react with these chromogens, so reagents add a masking agent such as thiourea. Hemolyzed samples are unsuitable because red cells contain iron.
- A: Copper is masked with a separate agent such as thiourea.
- B: Ferritin iron is not part of serum iron and is not released by this step.
- D: The chromogen needs ferrous iron; ferric iron is the form carried on transferrin.
Question 5 · Easy
Total iron-binding capacity (TIBC) is an indirect measure of which plasma protein?
1. AHemosiderin
2. BCeruloplasmin
3. CTransferrin
4. DFerritin
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Answer: C · Transferrin
TIBC is the maximum amount of iron that serum proteins can bind, and nearly all of that binding is by transferrin. Each transferrin molecule carries up to two ferric iron atoms. Transferrin rises in iron deficiency, pregnancy and estrogen use, and falls in inflammation, liver disease and protein loss. Transferrin can also be measured directly by immunoassay.
- A: Hemosiderin is an insoluble storage form inside cells.
- B: Ceruloplasmin is a copper protein with ferroxidase activity, not an iron carrier.
- D: Ferritin is the iron storage protein and is measured separately.
Question 6 · Medium
Serum iron is drawn 2 hours after the patient's oral iron tablet. Compared with a fasting sample taken the day before, the results will most likely show:
1. ALowered iron and saturation
2. BRaised iron and saturation
3. CLowered ferritin with normal iron
4. DRaised TIBC with normal iron
Answer and explanation in LearnFree account
Question 7 · Hard
A patient's serum iron is 50 µg/dL (9.0 µmol/L) and the transferrin saturation is 10%. What is the UIBC?
1. A5 µg/dL (0.9 µmol/L)
2. B550 µg/dL (98.5 µmol/L)
3. C450 µg/dL (80.6 µmol/L)
4. D500 µg/dL (89.5 µmol/L)
Answer and explanation in LearnFree account
Question 8 · Hard
Serum iron is 40 µg/dL (7.2 µmol/L) and the unsaturated iron-binding capacity (UIBC) is 410 µg/dL (73.4 µmol/L). What are the TIBC and the transferrin saturation?
1. ATIBC 410 µg/dL; saturation 10%
2. BTIBC 450 µg/dL; saturation 9%
3. CTIBC 370 µg/dL; saturation 11%
4. DTIBC 450 µg/dL; saturation 91%
Answer and explanation in LearnFree account
Question 9 · Medium
In a direct TIBC method, excess iron is added to saturate transferrin, and light magnesium carbonate is then added. Its purpose is to:
1. ARemove the excess iron left unbound
2. BPrecipitate the serum proteins
3. CReduce ferric to ferrous iron
4. DRelease iron from transferrin
Answer and explanation in LearnFree account
Question 10 · Medium
Low serum iron, high total iron-binding capacity and low ferritin suggest which condition?
1. AHereditary hemochromatosis
2. BBeta-thalassemia trait
3. CIron deficiency anemia
4. DAnemia of chronic disease
Answer and explanation in LearnFree account

Iron, TIBC and trace elements

A UIBC assay adds 500 µg/dL of iron to serum, and 150 µg/dL is left unbound after transferrin takes up what it can. Serum iron is 60 µg/dL (10.7 µmol/L). The TIBC is:

A 48-year-old man with fatigue, joint pain and a raised ALT has serum iron 210 µg/dL (37.6 µmol/L), TIBC 250 µg/dL (44.8 µmol/L) and ferritin 1,450 ng/mL (1,450 µg/L). His transferrin saturation and its meaning are:

In most serum iron methods, iron is freed from transferrin at acid pH and then reduced before ferrozine is added. Why is the reduction step needed?

Total iron-binding capacity (TIBC) is an indirect measure of which plasma protein?

Serum iron is drawn 2 hours after the patient's oral iron tablet. Compared with a fasting sample taken the day before, the results will most likely show:

A patient's serum iron is 50 µg/dL (9.0 µmol/L) and the transferrin saturation is 10%. What is the UIBC?

Serum iron is 40 µg/dL (7.2 µmol/L) and the unsaturated iron-binding capacity (UIBC) is 410 µg/dL (73.4 µmol/L). What are the TIBC and the transferrin saturation?

In a direct TIBC method, excess iron is added to saturate transferrin, and light magnesium carbonate is then added. Its purpose is to:

Low serum iron, high total iron-binding capacity and low ferritin suggest which condition?