Medical Laboratory Technologist Prometric exam questions with answers

1. Question 1General Laboratory, Quality Management & Safetymedium

   On a chemistry analyser, the same level of control material gives values above +2 SD on two consecutive runs, while the other level is within limits. Which interpretation and action are correct under Westgard rules?

   1. AA 1-2s warning only; accept the run and continue testing
   2. BA 2-2s violation (systematic error); reject the run and investigate
   3. CAn R-4s violation suggesting random error; repeat one control
   4. DA 10x violation; no action until ten results are available
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   Answer: B. A 2-2s violation (systematic error); reject the run and investigate

   Two consecutive control values exceeding the same 2 SD limit is a 2-2s rule violation, which points to systematic error such as calibration drift or reagent deterioration, so patient results are held and the cause is investigated. A 1-2s result is only a warning when a single value is outside 2 SD, which does not apply when the rule has already been broken on consecutive runs.

2. Question 2Clinical Chemistryeasy

   A blood sample arrives visibly haemolysed after a difficult venepuncture. Which analyte is most likely to be falsely increased?

   1. ASodium
   2. BGlucose
   3. CAlbumin
   4. DPotassium
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   Answer: D. Potassium

   Red cells contain far more potassium than plasma, so in vitro haemolysis releases potassium and falsely raises the result; LDH, AST and phosphate are also increased. Sodium is mainly extracellular and is not significantly raised by haemolysis, and glucose is more affected by delayed separation than by haemolysis.

3. Question 3Clinical Chemistrymedium

   A patient with suspected ketoacidosis has sodium 140 mmol/L, potassium 4.5 mmol/L, chloride 100 mmol/L and bicarbonate 10 mmol/L. Using the formula that excludes potassium, what is the anion gap?

   1. A30 mmol/L
   2. B10 mmol/L
   3. C50 mmol/L
   4. D20 mmol/L
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   Answer: A. 30 mmol/L

   Anion gap = Na - (Cl + HCO3) = 140 - (100 + 10) = 30 mmol/L, which is raised and consistent with a high anion gap metabolic acidosis such as ketoacidosis. A result of 50 mmol/L comes from adding bicarbonate instead of subtracting it, and the usual reference range without potassium is roughly 8-16 mmol/L.

4. Question 4Clinical Chemistryhard

   An outpatient who is clinically well with a normal ECG has serum potassium 9.6 mmol/L, calcium 0.6 mmol/L (2.4 mg/dL) and a very low alkaline phosphatase. The sample is not haemolysed. What is the most likely explanation?

   1. AAcute kidney injury with severe hyperkalaemia
   2. BPrimary hypoparathyroidism with renal tubular acidosis
   3. CContamination of the serum sample with K2EDTA anticoagulant
   4. DPseudohyperkalaemia caused by a high platelet count
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   Answer: C. Contamination of the serum sample with K2EDTA anticoagulant

   K2EDTA contamination, for example from an incorrect order of draw or decanting, adds potassium and chelates calcium, magnesium and zinc, giving spurious hyperkalaemia, profound hypocalcaemia and low ALP (a zinc and magnesium dependent enzyme) in a well patient; the sample should be recollected. True hyperkalaemia at this level would almost always produce ECG changes, and thrombocytosis does not explain the hypocalcaemia.

5. Question 5Hematologymedium

   A 35-year-old woman has fever, confusion, anaemia, a platelet count of 18 x 10^9/L, raised LDH and impaired renal function. Coagulation screen is normal. Which blood film finding most supports thrombotic thrombocytopenic purpura?

   1. ASpherocytes (dense round red cells)
   2. BTarget cells (codocytes)
   3. CSchistocytes (fragmented red cells)
   4. DBite cells (degmacytes)
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   Answer: C. Schistocytes (fragmented red cells)

   TTP is a thrombotic microangiopathy, in which red cells are sheared by microthrombi, producing schistocytes with thrombocytopenia and haemolysis; a normal coagulation screen helps distinguish it from DIC. Spherocytes are typical of hereditary spherocytosis and warm autoimmune haemolysis, and bite cells suggest oxidative haemolysis such as G6PD deficiency.

6. Question 6Hematologyhard

   A child with intermittent jaundice and splenomegaly has a raised MCHC, numerous spherocytes on the film, a negative direct antiglobulin test and a family history of similar problems. Which test is preferred to confirm the likely diagnosis?

   1. AEosin-5-maleimide (EMA) binding test
   2. BHaemoglobin electrophoresis by HPLC
   3. CQuantitative G6PD enzyme assay
   4. DHam acid serum lysis test
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   Answer: A. Eosin-5-maleimide (EMA) binding test

   Spherocytes with a raised MCHC, a negative DAT and a positive family history suggest hereditary spherocytosis, and the EMA binding test, which detects reduced band 3 on the red cell membrane, is the recommended screening and confirmation test. The negative DAT excludes autoimmune haemolysis, while haemoglobin electrophoresis assesses haemoglobinopathies rather than membrane defects.

7. Question 7Hematologyeasy

   Needle-shaped azurophilic inclusions are seen in the cytoplasm of blasts on a bone marrow aspirate. These Auer rods indicate which condition?

   1. AAcute lymphoblastic leukaemia
   2. BChronic lymphocytic leukaemia
   3. CChronic myeloid leukaemia in chronic phase
   4. DAcute myeloid leukaemia
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   Answer: D. Acute myeloid leukaemia

   Auer rods are fused primary (azurophilic) granules and are found in myeloid blasts, so they confirm a myeloid lineage and are characteristic of AML, particularly acute promyelocytic leukaemia. Lymphoblasts in ALL do not contain Auer rods, which is why they are a useful morphological discriminator.

8. Question 8Coagulation & Hemostasismedium

   A patient who takes no medication has a prolonged prothrombin time with a normal activated partial thromboplastin time. Deficiency of which single factor best explains this pattern?

   1. AFactor VIII
   2. BFactor VII
   3. CFactor IX
   4. DFactor XII
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   Answer: B. Factor VII

   Factor VII is the only factor unique to the extrinsic pathway measured by the PT, so its deficiency prolongs the PT alone. Deficiencies of factors VIII, IX and XII affect the intrinsic pathway and prolong the aPTT with a normal PT.

9. Question 9Coagulation & Hemostasishard

   A coagulation sample is requested on a patient with polycythaemia whose haematocrit is 65%. What adjustment is needed to avoid falsely prolonged clotting times?

   1. AReduce the volume of sodium citrate in the tube before collection
   2. BIncrease the volume of sodium citrate in the tube before collection
   3. CCollect the sample into a lithium heparin tube instead
   4. DUnderfill the standard citrate tube to about half its volume
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   Answer: A. Reduce the volume of sodium citrate in the tube before collection

   With a very high haematocrit, the plasma volume is small, so the standard citrate volume is excessive relative to plasma, causing over-anticoagulation and falsely prolonged PT and aPTT; CLSI guidance is to reduce citrate volume when the haematocrit exceeds 55%. Adding more citrate or underfilling the tube would worsen the citrate-to-plasma excess.

10. Question 10Immunology & Serologymedium

    A healthcare worker's hepatitis B serology shows HBsAg negative, total anti-HBc positive and anti-HBs positive. How should this be interpreted?

    1. AImmunity from hepatitis B vaccination only, with no past infection
    2. BChronic hepatitis B infection with ongoing viral replication
    3. CPast hepatitis B infection that has resolved, with natural immunity
    4. DAcute hepatitis B infection in the window period
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    Answer: C. Past hepatitis B infection that has resolved, with natural immunity

    Anti-HBc is produced only after natural infection, and anti-HBs with a negative HBsAg indicates clearance and immunity, so the pattern represents resolved past infection. Vaccination produces anti-HBs alone without anti-HBc, which is the most common source of confusion. Chronic infection would show a positive HBsAg.

11. Question 11Immunohematology (Blood Group Serology)hard

    Ten days after a red cell transfusion, a patient develops falling haemoglobin, mild jaundice and a newly positive DAT. The pre-transfusion antibody screen was negative. Which antibody is classically implicated in this type of reaction?

    1. AAnti-Lea
    2. BAnti-Jka
    3. CAnti-M
    4. DAnti-P1
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    Answer: B. Anti-Jka

    Kidd antibodies such as anti-Jka are notorious for causing delayed haemolytic transfusion reactions because they often fall to undetectable levels and then rise rapidly on re-exposure (an anamnestic response); they also show dosage. Lewis, M and P1 antibodies are usually IgM, cold-reactive and rarely clinically significant, so they are unlikely causes.

12. Question 12Blood Banking & Transfusion Serviceseasy

    A trauma patient of unknown blood group needs plasma urgently. Which ABO group of plasma can be given safely before the patient's group is known?

    1. AGroup O
    2. BGroup A
    3. CGroup B
    4. DGroup AB
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    Answer: D. Group AB

    Group AB plasma contains neither anti-A nor anti-B, so it is compatible with recipients of any ABO group and is the universal plasma donor group. Group O is the universal donor for red cells, but group O plasma contains both anti-A and anti-B and can haemolyse non-O red cells.

13. Question 13Blood Banking & Transfusion Servicesmedium

    How should platelet concentrates be stored to maintain their function until transfusion?

    1. AAt 2-6 C in a monitored blood bank refrigerator
    2. BAt 20-24 C without agitation to avoid activation
    3. CAt -18 C or colder in a plasma freezer
    4. DAt 20-24 C with continuous gentle agitation
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    Answer: D. At 20-24 C with continuous gentle agitation

    Platelets are stored at room temperature (20-24 C) with continuous agitation to maintain gas exchange and pH and preserve function, usually for 5-7 days depending on the system. Refrigeration causes cold-induced clearance of standard platelets, and storing without agitation leads to a fall in pH and loss of viability. Room-temperature storage also makes bacterial contamination the main infective risk.

14. Question 14Microbiologymedium

    A wound swab grows a non-lactose fermenting Gram-negative rod on MacConkey agar. It is oxidase positive, produces a blue-green pigment and has a grape-like odour. Which organism is most likely?

    1. APseudomonas aeruginosa
    2. BEscherichia coli
    3. CKlebsiella pneumoniae
    4. DProteus mirabilis
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    Answer: A. Pseudomonas aeruginosa

    Pseudomonas aeruginosa is an oxidase-positive non-fermenter that produces pyocyanin (blue-green pigment) and a characteristic grape-like odour. Proteus mirabilis is also a non-lactose fermenter but is oxidase negative and swarms on blood agar, while E. coli and Klebsiella are lactose fermenters.

15. Question 15Urinalysis & Body Fluidseasy

    A urine reagent strip shows a positive nitrite pad. What does this most likely indicate?

    1. AInfection with Enterococcus faecalis
    2. BBacteriuria with nitrate-reducing organisms such as E. coli
    3. CCandida infection of the urinary tract
    4. DContamination of the sample with vaginal epithelial cells
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    Answer: B. Bacteriuria with nitrate-reducing organisms such as E. coli

    Many Gram-negative Enterobacterales, such as E. coli, reduce dietary nitrate to nitrite, so a positive nitrite test indicates significant bacteriuria. Enterococci and yeasts do not reduce nitrate, so a negative nitrite does not exclude infection with these organisms.

Last reviewed September 2026. Questions are original and written to the published exam blueprint; they are not taken from any real paper.