Proteins: physiology (total protein, albumin, globulins, specific proteins)

11 ASCP MLS practice questions on Proteins: physiology (total protein, albumin, globulins, specific proteins), part of Chemistry. The first 11 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

1. Question 1 · Hard

   A 30-year-old man is admitted with pneumonia. On day 3 of treatment his hemoglobin falls from 14.2 to 10.1 g/dL [142 to 101 g/L] and his urine turns dark. Results: reticulocytes 6.5%, LD 690 U/L (reference 125-220), total bilirubin 3.6 mg/dL [62 µmol/L] with direct bilirubin 0.4 mg/dL [7 µmol/L], DAT negative. The smear shows bite and blister cells, and G6PD activity is later found to be low. CRP is 185 mg/L (below 10), and haptoglobin is 96 mg/dL [0.96 g/L] (reference 30-200). Why is the haptoglobin within the reference range?

   1. AInflammation has raised haptoglobin synthesis
   2. BLysed red cells have released haptoglobin
   3. COxidative hemolysis does not consume haptoglobin
   4. DHemopexin has bound the free hemoglobin first

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   Answer: A · Inflammation has raised haptoglobin synthesis

   Haptoglobin binds free hemoglobin, and the complex is quickly removed by macrophages, so the level usually falls in hemolysis. But haptoglobin is also a positive acute phase protein: IL-6 from the pneumonia drives the liver to make more, as the very high CRP shows. Increased synthesis can balance consumption and leave a normal level that hides active hemolysis. Here the falling hemoglobin, raised reticulocytes, high LD, raised indirect bilirubin and bite cells show the hemolysis anyway. A normal haptoglobin during inflammation therefore does not rule out hemolysis.

   • B: Haptoglobin is made by the liver; red cells do not contain it.
   • C: Hemoglobin from G6PD hemolysis binds haptoglobin like any other free hemoglobin.
   • D: Hemopexin binds free heme only after haptoglobin is used up.

2. Question 2 · Easy

   Albumin, fibrinogen and most acute phase proteins are made by:

   1. APlasma cells
   2. BRenal tubular cells
   3. CVascular endothelium
   4. DHepatocytes

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   Answer: D · Hepatocytes

   The liver makes almost all plasma proteins except the immunoglobulins, which come from plasma cells. During inflammation, hepatocytes change their output, raising CRP, fibrinogen and haptoglobin and lowering albumin. Severe liver disease therefore lowers albumin and the clotting factors. Immunoglobulins are still made in cirrhosis, so globulins are often normal or raised while albumin falls.

   • A: Plasma cells make immunoglobulins, not albumin or fibrinogen.
   • B: The kidney filters and reabsorbs proteins but makes few plasma proteins.
   • C: Endothelium makes von Willebrand factor, not albumin or fibrinogen.

3. Question 3 · Medium

   Transthyretin (prealbumin) reflects recent changes in protein nutrition better than albumin does, mainly because it:

   1. ABinds most of the plasma calcium
   2. BIs made by plasma cells, not liver
   3. CIs unaffected by acute inflammation
   4. DHas a much shorter half-life, about 2 days

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   Answer: D · Has a much shorter half-life, about 2 days

   Transthyretin has a half-life of about 2 days, compared with about 3 weeks for albumin, so it responds within days to a change in intake. It is still a negative acute phase reactant, so inflammation lowers it whatever the nutritional state, and checking CRP at the same time helps interpretation. It is made in the liver and carries thyroxine and retinol-binding protein. Albumin, not transthyretin, binds most of the protein-bound calcium.

   • A: Albumin carries most of the protein-bound calcium.
   • B: It is made by the liver.
   • C: It falls in inflammation, so CRP should be checked at the same time.

4. Question 4 · Hard

   An hs-CRP ordered for cardiovascular risk assessment in a 52-year-old woman is 14 mg/L. She had a sore throat last week. What is the most appropriate next step?

   1. AReport her as high cardiovascular risk
   2. BReport her as low cardiovascular risk
   3. CConfirm the result with a conventional CRP
   4. DRepeat in about 2 weeks once she is well

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   Answer: D · Repeat in about 2 weeks once she is well

   For cardiovascular risk, hs-CRP below 1 mg/L is low risk, 1 to 3 mg/L average and above 3 mg/L high risk, ideally based on two results taken about 2 weeks apart. A value above 10 mg/L points to acute infection or inflammation, so it is not used for risk, and the test is repeated when the patient is well. A standard CRP assay gives the same answer at this level, so retesting by another method adds nothing. hs-CRP is meant for people who are clinically stable and free of infection.

   • A: A value over 10 mg/L reflects acute inflammation and is not used for risk.
   • B: 14 mg/L is far above the low-risk range of less than 1 mg/L.
   • C: A standard CRP gives the same answer at this level and adds nothing.

5. Question 5 · Hard

   A 29-year-old woman with SLE has a fever. ESR 88 mm/h, CRP 175 mg/L (reference < 10 mg/L) and procalcitonin 6.0 ng/mL (reference < 0.1 ng/mL). The best interpretation is:

   1. ALupus flare without infection
   2. BDrug-induced lupus flare
   3. CLikely viral infection
   4. DLikely bacterial infection

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   Answer: D · Likely bacterial infection

   In an SLE flare the ESR is often high, but CRP usually stays normal or only mildly raised unless there is serositis or arthritis. A CRP this high, together with a procalcitonin far above the reference range, strongly suggests bacterial infection. Viral infections usually give only small CRP rises and a low procalcitonin. Cultures should be taken and treatment for infection started promptly in this immunosuppressed patient.

   • A: A lupus flare alone seldom gives a CRP this high with a raised procalcitonin.
   • B: Drug-induced lupus would not explain the high procalcitonin.
   • C: Viral infection usually gives a small CRP rise and a low procalcitonin.

6. Question 6 · Medium

   Why is CRP better than the ESR for following a patient's response to antibiotic treatment?

   1. AIt is not raised after surgery or trauma
   2. BIt does not depend on liver synthesis
   3. CIt falls soon after inflammation subsides
   4. DIt rises only in bacterial infection

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7. Question 7 · Easy

   The cytokine that mainly drives the liver to make CRP and other acute phase proteins is:

   1. AInterleukin-4
   2. BInterleukin-6
   3. CInterleukin-2
   4. DInterferon-gamma

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8. Question 8 · Medium

   A ceruloplasmin within the reference range does not fully exclude Wilson disease in a patient with active inflammation, because ceruloplasmin:

   1. ARises as an acute phase reactant
   2. BIs made by macrophages during infection
   3. CFalls as a negative acute phase reactant
   4. DBinds copper only when CRP is normal

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9. Question 9 · Easy

   Which of these proteins falls during an acute inflammatory response?

   1. AFibrinogen
   2. BAlbumin
   3. CC-reactive protein
   4. DHaptoglobin

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10. Question 10 · Hard

    Day 3 after major bowel surgery, a previously well-nourished patient has albumin 2.6 g/dL [26 g/L] (3.5-5.0), transthyretin 10 mg/dL [100 mg/L] (20-40) and CRP 190 mg/L (< 10). Bilirubin and INR are normal. The low albumin and transthyretin mainly reflect:

    1. ANephrotic syndrome
    2. BThe acute phase response
    3. CAcute liver failure
    4. DProtein-calorie malnutrition

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11. Question 11 · Medium

    A 38-year-old non-smoker has emphysema mainly in the lung bases and mildly raised liver enzymes. Deficiency of which protein is most likely?

    1. AAlpha-2 macroglobulin
    2. BCeruloplasmin
    3. CAlpha-1 antitrypsin
    4. DHaptoglobin

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