Free Medical Laboratory Technologist mock test

Medical Laboratory Technologist sample questions with answers

10 more original exam-style Medical Laboratory Technologist questions, worked in full. They are not real or recalled exam questions, and none of them is in the mock above or on the bank page, so sit the mock first if you have not.

1. Question 1 · Clinical Chemistry

   A patient has a total serum calcium of 7.6 mg/dL (low) and an albumin of 2.0 g/dL. After correcting for the low albumin, the calcium is within normal limits. This illustrates that total calcium is affected by albumin because:

   1. AApproximately half of serum calcium is bound to albumin and other proteins
   2. BAlbumin directly synthesizes calcium
   3. CIonized calcium always falls when albumin is low
   4. DAlbumin increases calcium excretion in urine
   Show answer and explanation

   Correct answer: A. Approximately half of serum calcium is bound to albumin and other proteins

   About 40-50% of serum calcium is protein-bound, mainly to albumin, so hypoalbuminemia lowers total calcium while the physiologically active ionized calcium may remain normal. The corrected calcium formula (add 0.8 mg/dL per 1 g/dL albumin below 4.0) accounts for this. Ionized calcium is not necessarily reduced, and albumin does not synthesize or excrete calcium.

   Reference: Tietz Textbook of Clinical Chemistry and Molecular Diagnostics, 6th ed., 2018

2. Question 2 · Microbiology

   A modified acid-fast stain using a weaker (1% sulfuric acid) decolorizer, rather than the standard acid-alcohol, is preferred to demonstrate which organism because it is only partially acid-fast?

   1. AMycobacterium tuberculosis
   2. BNocardia species
   3. CStaphylococcus aureus
   4. DEscherichia coli
   Show answer and explanation

   Correct answer: B. Nocardia species

   Nocardia species are only partially (weakly) acid-fast and lose the stain with the strong acid-alcohol used for mycobacteria, so a weaker decolorizer (modified Kinyoun) is used to retain the carbolfuchsin. M. tuberculosis is strongly acid-fast and demonstrated by standard Ziehl-Neelsen; Staphylococcus and E. coli are not acid-fast at all.

   Reference: Tille, Bailey & Scott's Diagnostic Microbiology, 15th ed. (Elsevier, 2022)

3. Question 3 · Blood Banking & Transfusion Services

   During a transfusion reaction workup, the post-transfusion direct antiglobulin test (DAT) is positive but the pretransfusion DAT was negative. What does this finding most strongly suggest?

   1. ABacterial contamination of the unit
   2. BIn vivo coating of transfused donor red cells by recipient antibody, consistent with a hemolytic reaction
   3. CVolume overload
   4. DAllergic reaction to plasma proteins
   Show answer and explanation

   Correct answer: B. In vivo coating of transfused donor red cells by recipient antibody, consistent with a hemolytic reaction

   A newly positive post-transfusion DAT indicates recipient antibody has coated transfused donor cells in vivo, supporting an immune hemolytic reaction (often a mixed-field pattern). Bacterial contamination is assessed by culture and Gram stain, TACO and allergic reactions do not produce a positive DAT.

   Reference: AABB Technical Manual, 20th ed.

4. Question 4 · Coagulation & Hemostasis

   Factor XIII (fibrin stabilizing factor) deficiency should be suspected in a patient with delayed bleeding and poor wound healing despite which laboratory finding?

   1. AProlonged PT and aPTT
   2. BNormal PT, aPTT, thrombin time, and platelet count
   3. CMarkedly reduced fibrinogen concentration
   4. DProlonged thrombin time with normal PT
   Show answer and explanation

   Correct answer: B. Normal PT, aPTT, thrombin time, and platelet count

   Factor XIII cross-links fibrin monomers to stabilize the clot but acts after fibrin polymerization, so routine screening tests (PT, aPTT, thrombin time, fibrinogen, platelets) are all normal in factor XIII deficiency. Diagnosis requires a specific clot solubility test (5M urea) or a factor XIII activity assay, so a normal coagulation screen with clinical bleeding is the classic clue.

   Reference: Rodak's Hematology, 6th ed., 2020; ISTH guidance on factor XIII deficiency

5. Question 5 · General Laboratory, Quality Management & Safety

   On a brightfield microscope, progressively closing the condenser (aperture) iris diaphragm will:

   1. AIncrease resolution while decreasing contrast
   2. BIncrease the field of view without affecting image quality
   3. CIncrease contrast but decrease resolution
   4. DHave no measurable effect on the image
   Show answer and explanation

   Correct answer: C. Increase contrast but decrease resolution

   The aperture (condenser) iris diaphragm controls the numerical aperture of the illumination. Closing it increases contrast and depth of field but reduces the effective numerical aperture, thereby lowering resolution. Field of view is governed by the field diaphragm and eyepiece, not the aperture diaphragm.

   Reference: Turgeon ML, Clinical Laboratory Science: Concepts, Procedures, and Clinical Applications, 8th ed. (Elsevier, 2020)

6. Question 6 · Hematology

   A 30-year-old's bone marrow biopsy is estimated to be 70% cellular. Using the common age-based rule of thumb (cellularity approximately equals 100 minus age), this finding is best interpreted as:

   1. AMarkedly hypocellular
   2. BAplastic
   3. CMarkedly hypercellular
   4. DApproximately normocellular
   Show answer and explanation

   Correct answer: D. Approximately normocellular

   A rough estimate of expected marrow cellularity is 100 minus the patient's age, giving about 70% for a 30-year-old, so 70% cellularity is approximately normal for this age. It is not hypocellular, aplastic, or markedly hypercellular by this estimate.

   Reference: Rodak's Hematology: Clinical Principles and Applications, 6th ed. (2020)

7. Question 7 · Immunohematology (Blood Group Serology)

   During tube typing, a technologist observes one solid aggregate of red cells with a clear background after resuspension. Which grade of agglutination best describes this reaction?

   1. A4+
   2. B2+
   3. C1+
   4. DMixed-field
   Show answer and explanation

   Correct answer: A. 4+

   A single solid agglutinate with a clear (cell-free) supernatant is the strongest reaction and is graded 4+. A 2+ reaction shows several medium-sized clumps in a turbid background, and 1+ shows many small clumps with a turbid, reddish background. Mixed-field describes a few small agglutinates among many free unagglutinated cells, not a single solid clump.

   Reference: Harmening, Modern Blood Banking and Transfusion Practices, 7th edition, 2019

8. Question 8 · Urinalysis & Body Fluids

   A patient presents after a crush injury with red-brown urine. The reagent strip blood pad is strongly positive, yet microscopic examination shows no red blood cells and the plasma is clear/straw-colored rather than pink. These findings most strongly support which diagnosis?

   1. AMyoglobinuria from rhabdomyolysis
   2. BIntravascular hemolysis with hemoglobinuria
   3. CHematuria from lower urinary tract bleeding
   4. DPorphyrinuria from acute porphyria
   Show answer and explanation

   Correct answer: A. Myoglobinuria from rhabdomyolysis

   A positive blood pad with no RBCs on microscopy indicates either myoglobin or hemoglobin. Myoglobin is a small molecule that does not bind haptoglobin and is rapidly cleared, so plasma stays clear/straw-colored, whereas free hemoglobin binds haptoglobin and discolors plasma pink, making option 2 unlikely here. The crush-injury history points to rhabdomyolysis. Intact RBCs would be seen in true hematuria (option 3), and porphyrins do not react with the peroxidase-based blood pad (option 4).

   Reference: Brunzel, Fundamentals of Urine and Body Fluid Analysis, 4th ed. (2018)

9. Question 9 · Immunology & Serology

   Which feature most clearly distinguishes adaptive immunity from innate immunity?

   1. ARecognition of conserved pathogen-associated molecular patterns
   2. BImmediate response within minutes of exposure
   3. CImmunologic memory with a more rapid, robust secondary response
   4. DReliance on physical barriers such as skin and mucosa
   Show answer and explanation

   Correct answer: C. Immunologic memory with a more rapid, robust secondary response

   Immunologic memory, producing a faster and stronger response on re-exposure, is a defining hallmark of adaptive immunity. Recognition of conserved PAMPs by pattern-recognition receptors, immediate responses, and physical barriers are all characteristics of innate immunity, which lacks true antigen-specific memory.

   Reference: Abbas, Lichtman & Pillai, Cellular and Molecular Immunology, 10th ed., 2022

10. Question 10 · Clinical Chemistry

    A patient's total serum calcium is reported as 7.8 mg/dL (reference 8.6-10.2 mg/dL) but the patient is asymptomatic. The serum albumin is low at 2.0 g/dL (reference 3.5-5.0 g/dL). After correcting calcium for the low albumin, what is the most likely interpretation?

    1. ATrue hypocalcemia requiring urgent calcium replacement
    2. BCorrected calcium is approximately normal; the low total value reflects hypoalbuminemia
    3. CThe result indicates primary hyperparathyroidism
    4. DThe specimen must be contaminated with EDTA
    Show answer and explanation

    Correct answer: B. Corrected calcium is approximately normal; the low total value reflects hypoalbuminemia

    About 40% of total calcium is albumin-bound, so hypoalbuminemia lowers total calcium without affecting the physiologically active ionized fraction. Using the correction of roughly +0.8 mg/dL per 1.0 g/dL decrease in albumin below 4.0 g/dL, the corrected calcium (7.8 + 0.8 x 2.0 = 9.4 mg/dL) is normal, explaining why the patient is asymptomatic. This is pseudohypocalcemia, not true hypocalcemia or hyperparathyroidism, and EDTA contamination would markedly lower calcium and typically elevate potassium, not fit this picture.

    Reference: Payne RB et al., BMJ, albumin-adjusted calcium (1973); Tietz Textbook of Clinical Chemistry and Molecular Diagnostics, 6th ed. (2018)