Other studies (ESR, G6PD, Heinz bodies)

5 ASCP MLS practice questions on Other studies (ESR, G6PD, Heinz bodies), part of Hematology. The first 5 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 · Easy

   What does the fluorescent spot screening test for G6PD deficiency detect?

   1. ANADPH formed from NADP+ by the enzyme
   2. BMethemoglobin formed by nitrite
   3. CNADH made from NAD+ by the enzyme
   4. DHeinz bodies formed after an oxidant

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   Answer: A · NADPH formed from NADP+ by the enzyme

   In the fluorescent spot test, lysed red cells are given glucose-6-phosphate and NADP+. Normal G6PD reduces NADP+ to NADPH, which fluoresces under long-wave ultraviolet light, while a deficient sample shows little or no fluorescence. A quantitative spectrophotometric assay measures the rate of NADPH formation at 340 nm. Female heterozygotes with mixed normal and deficient cells can be missed by the screen, so quantitative testing is used when the result matters.

   • B: Nitrite-made methemoglobin is used in an older, different screening method.
   • C: G6PD uses NADP+, not NAD+.
   • D: Heinz bodies are seen with a supravital stain, not in this enzyme screen.

2. Question 2 · Hard

   A 22-year-old with sickle cell anemia (Hb SS) has osteomyelitis. CRP is 120 mg/L, hemoglobin 7.4 g/dL (74 g/L), and the film shows many sickled cells. The ESR, set up within 1 hour of collection, is 4 mm/h. What best explains the low ESR?

   1. AHigh CRP blocking rouleaux formation
   2. BFibrinogen used up during the crisis
   3. CSevere anemia slows red cell settling
   4. DSickled cells are unable to form rouleaux

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   Answer: D · Sickled cells are unable to form rouleaux

   The ESR depends on red cells stacking into rouleaux, which fall faster than single cells. Rigid, irregular cells such as sickle cells, spherocytes and acanthocytes cannot stack, so the ESR stays low even with marked inflammation. Anemia normally raises the ESR, so it cannot explain a low value here. In patients with Hb SS, CRP is a more reliable marker of inflammation.

   • A: A high CRP signals inflammation, which should raise the ESR, not lower it.
   • B: Fibrinogen rises as an acute-phase protein in infection; it is not used up.
   • C: Anemia speeds sedimentation; it does not slow it.

3. Question 3 · Easy

   If a Westergren ESR tube is tilted away from vertical during the test, the result will be:

   1. AFalsely increased
   2. BToo variable to read
   3. CFalsely decreased
   4. DUnaffected

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   Answer: A · Falsely increased

   In a tilted tube, red cells slide down the lower wall while plasma rises along the upper wall, so the cells settle faster. Even a small tilt raises the ESR noticeably, so the tube must stand exactly vertical in a rack free of vibration. A warm room also speeds sedimentation. Excess anticoagulant and long delays before testing do the opposite and falsely lower the ESR.

   • B: The cell-plasma boundary can still be read; it simply falls faster.
   • C: Excess anticoagulant and delays lower the ESR; tilting raises it.
   • D: Tilting changes how fast the cells settle.

4. Question 4 · Medium

   A patient in a rheumatoid arthritis flare has a markedly raised ESR. Which change most explains the faster sedimentation?

   1. AA higher hematocrit from dehydration
   2. BMore fibrinogen and globulins, promoting rouleaux
   3. CA rise in serum albumin, promoting rouleaux
   4. DMore sickle-shaped red cells in the blood

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   Answer: B · More fibrinogen and globulins, promoting rouleaux

   Fibrinogen and globulins, which rise in inflammation, reduce the negative charge (zeta potential) that keeps red cells apart. The cells stack into rouleaux, which are heavier and fall faster. That is why the ESR is a non-specific marker of inflammation. Abnormally shaped cells and a high hematocrit slow sedimentation instead.

   • A: A high red cell mass slows sedimentation.
   • C: Albumin tends to slow rouleaux formation rather than speed it.
   • D: Sickle cells cannot stack into rouleaux, so they lower the ESR.

5. Question 5 · Medium

   Which red cell inclusion is made of denatured hemoglobin and needs a supravital stain to be seen?

   1. AHowell-Jolly bodies
   2. BPappenheimer bodies
   3. CHeinz bodies
   4. DBasophilic stippling

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   Answer: C · Heinz bodies

   Heinz bodies are clumps of oxidized, denatured hemoglobin attached to the red cell membrane. They are not visible with Wright stain and need a supravital stain such as crystal violet or new methylene blue. They appear in G6PD deficiency after oxidant stress and with unstable hemoglobins. The spleen removes them, leaving bite cells.

   • A: Howell-Jolly bodies are DNA remnants visible on a Wright-stained film.
   • B: Pappenheimer bodies are iron granules visible on Wright stain and confirmed with Prussian blue.
   • D: Basophilic stippling is aggregated RNA visible on Wright stain, as in lead poisoning.