ESR and other routine tests

5 DOH Abu Dhabi (HAAD) lab licensing practice questions on ESR and other routine tests, 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 · Medium

   Which pair of findings would both tend to lower the ESR?

   1. AAnemia and a high fibrinogen
   2. BMacrocytosis and a tilted tube
   3. CHigh globulins and a warm room
   4. DSickle cells and a high hematocrit

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   Answer: D · Sickle cells and a high hematocrit

   Sickle cells cannot form rouleaux, and a high hematocrit slows the fall of the cells, so both lower the ESR. Anemia, high fibrinogen, high globulins, macrocytosis, a tilted tube and a warm room all raise it. A normal ESR therefore cannot rule out inflammation in a patient with sickle cell disease or polycythemia. CRP is a better marker of inflammation in these patients.

   • A: Both raise the ESR: anemia through fewer cells, fibrinogen by promoting rouleaux.
   • B: Large cells settle faster and a tilted tube speeds the fall, so both raise it.
   • C: Globulins promote rouleaux and warmth lowers viscosity, so both raise it.

2. Question 2 · Easy

   For the Westergren ESR with sodium citrate as the anticoagulant, blood and citrate are mixed in a ratio of:

   1. A4 parts blood to 1 part citrate
   2. B9 parts blood to 1 part citrate
   3. C1 part blood to 1 part citrate
   4. D1 part blood to 4 parts citrate

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   Answer: A · 4 parts blood to 1 part citrate

   The Westergren method uses 4 volumes of blood to 1 volume of sodium citrate; EDTA blood may instead be diluted 4:1 with citrate or saline. The 9:1 ratio belongs to coagulation tubes and would leave the blood too concentrated. The mixture is drawn into a 200 mm graduated tube, held exactly vertical, and read at 60 minutes. Under-filled or over-filled tubes alter the dilution and the result.

   • B: 9:1 is the ratio for coagulation tubes, not the ESR.
   • C: Equal parts would over-dilute the blood and speed sedimentation.
   • D: This inverts the ratio and would dilute the blood far too much.

3. Question 3 · Medium

   EDTA blood stored overnight at 4 °C is diluted and set up for a Westergren ESR straight from the refrigerator. Compared with the same blood at room temperature, the result is most likely:

   1. AUnchanged, as the test is read at 60 minutes
   2. BFalsely high, as stored red cells shrink
   3. CFalsely low, as cold blood is more viscous
   4. DFalsely high, as cold promotes rouleaux

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   Answer: C · Falsely low, as cold blood is more viscous

   The ESR is set up at room temperature (about 18-25 °C). Cold blood is more viscous and its red cells settle more slowly, so a sample tested straight from the refrigerator reads falsely low. Refrigerated EDTA samples must be brought to room temperature and mixed well before testing. Long storage also lowers the ESR, because the red cells become more spherical and form rouleaux poorly.

   • A: Temperature changes the rate of fall, so the 60-minute reading changes too.
   • B: Stored cells become more spherical, which lowers the ESR rather than raising it.
   • D: Cold slows sedimentation; it does not speed rouleaux formation.

4. Question 4 · Easy

   In the first phase of the ESR (about the first 10 minutes), the red cells mainly:

   1. AFall at their fastest, steady rate
   2. BSwell and lyse in the citrate
   3. CForm rouleaux and sink slowly
   4. DPack tightly at the bottom of the tube

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   Answer: C · Form rouleaux and sink slowly

   Sedimentation has three phases. In the lag phase, the cells form rouleaux and sink slowly. In the decantation phase, the larger aggregates fall at a fast, nearly constant rate, and this phase gives most of the reading. In the packing phase, the cells slow as they crowd at the bottom, so reading at exactly 60 minutes matters.

   • A: The fast, steady fall is the second (decantation) phase.
   • B: Red cells do not lyse in citrate during the test.
   • D: Packing is the last phase, when the cells crowd at the bottom.

5. Question 5 · Easy

   Which change in the blood tends to raise the ESR?

   1. ASickle cells
   2. BPolycythemia
   3. CAnemia
   4. DSpherocytes

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   Answer: C · Anemia

   With fewer red cells, plasma flows upward more freely as the cells fall, and rouleaux form more easily, so anemia raises the ESR. A high red cell count does the opposite. Abnormally shaped cells such as sickle cells and spherocytes cannot stack into rouleaux, so they lower the ESR. A raised ESR in an anemic patient must be read with this in mind.

   • A: Sickle cells cannot form rouleaux, so the ESR stays low.
   • B: A high red cell mass slows sedimentation and lowers the ESR.
   • D: Spherocytes do not stack into rouleaux, so the ESR is lowered.