DHA Hematology Laboratory exam questions

6 worked Hematology Laboratory practice questions

Original exam-style questions from the bank, spread across the blueprint domains. They are not real or recalled exam questions. Try each one, then open the answer for the rationale and reference. None of them appear in the free mock exam, so reading them will not spoil it.

1. Question 1 · Automation, Flow Cytometry and Quality Control

   An analyser reports a WBC of 12.0 x 10^9/L on a sample in which 20 nucleated red cells are counted per 100 white cells. What is the corrected WBC count?

   1. A9.6 x 10^9/L
   2. B14.4 x 10^9/L
   3. C10.0 x 10^9/L
   4. D11.8 x 10^9/L
   Show answer and explanation

   Correct answer: C. 10.0 x 10^9/L

   Corrected WBC = WBC x 100 / (100 + NRBC) = 12.0 x 100 / 120 = 10.0 x 10^9/L. Subtracting 20% of the count (giving 9.6) uses the wrong denominator.

   Reference: Dacie and Lewis Practical Haematology, 12th ed.

2. Question 2 · Haematopoiesis and Blood Cell Morphology

   A 70-year-old has a lymphocytosis of 28 x 10^9/L with many small mature lymphocytes and numerous smudge cells on the film. Which diagnosis is most likely?

   1. AAcute lymphoblastic leukaemia
   2. BInfectious mononucleosis
   3. CHairy cell leukaemia
   4. DChronic lymphocytic leukaemia
   Show answer and explanation

   Correct answer: D. Chronic lymphocytic leukaemia

   Smudge cells are fragile lymphocytes damaged during film spreading and are characteristic of CLL with a mature small lymphocytosis. Infectious mononucleosis shows large reactive lymphocytes rather than uniform small cells.

   Reference: Bain BJ. Blood Cells: A Practical Guide, 6th ed.

3. Question 3 · Haemostasis and Coagulation

   For routine PT and APTT testing, what blood-to-anticoagulant ratio is required in a 3.2% sodium citrate tube?

   1. A4:1
   2. B9:1
   3. C1:1
   4. D20:1
   Show answer and explanation

   Correct answer: B. 9:1

   Coagulation tubes require a 9:1 ratio of blood to 3.2% sodium citrate, and should be filled to at least 90% of the nominal volume. A 4:1 ratio is used for Westergren ESR tubes.

   Reference: CLSI H21-A5: Collection, Transport and Processing of Blood Specimens for Coagulation Testing

4. Question 4 · Haemostasis and Coagulation

   A patient with mild bleeding and thrombocytopenia shows platelet aggregation at a low ristocetin concentration that does not aggregate normal platelets. Which condition is suggested?

   1. AType 1 von Willebrand disease
   2. BBernard-Soulier syndrome
   3. CGlanzmann thrombasthenia
   4. DType 2B von Willebrand disease
   Show answer and explanation

   Correct answer: D. Type 2B von Willebrand disease

   Enhanced ristocetin-induced platelet aggregation at low ristocetin concentration reflects increased affinity of VWF for platelet GPIb, characteristic of type 2B VWD (or platelet-type VWD). Bernard-Soulier syndrome shows absent ristocetin aggregation.

   Reference: ASH/ISTH/NHF/WFH Guidelines on the Diagnosis of von Willebrand Disease 2021

5. Question 5 · Red Cell Disorders and Anaemia

   An analyser reports RBC 1.9 x 10^12/L, Hb 110 g/L, MCV 118 fL and MCHC 420 g/L, and the film shows red cell clumps. What is the most appropriate action?

   1. AReport the results with a comment
   2. BWarm the sample to 37 C and re-run
   3. CRequest a new sample in citrate
   4. DDilute the sample with water
   Show answer and explanation

   Correct answer: B. Warm the sample to 37 C and re-run

   Cold agglutinins clump red cells so that doublets are counted as single large cells, falsely lowering the RBC and raising MCV and MCHC; warming to 37 C disperses them. A new citrate sample does not prevent cold agglutination, and water would lyse the cells.

   Reference: Dacie and Lewis Practical Haematology, 12th ed.

6. Question 6 · Red Cell Disorders and Anaemia

   A child has spherocytes, a negative direct antiglobulin test and a family history of anaemia and gallstones. Which laboratory test is recommended for screening hereditary spherocytosis?

   1. AOsmotic fragility on fresh blood only
   2. BHb electrophoresis
   3. CEosin-5-maleimide (EMA) binding test
   4. DSickle solubility test
   Show answer and explanation

   Correct answer: C. Eosin-5-maleimide (EMA) binding test

   The EMA binding test by flow cytometry measures reduced band 3-related membrane proteins and is a sensitive, specific screening test for hereditary spherocytosis. Haemoglobin electrophoresis assesses haemoglobin variants, not membrane defects.

   Reference: BSH Guidelines for the Diagnosis and Management of Hereditary Spherocytosis 2011