MLT GlobeSCFHS exam preparation (Saudi Arabia) – page 23
749 practice MCQs for the SCFHS medical laboratory exam. Level: Intermediate.
After starting oral iron for iron deficiency anemia, the reticulocyte count is expected to peak at about:
A reticulocyte response starts in a few days and peaks at about 7–10 days. Hemoglobin then rises by roughly 1–2 g/dL every 2–3 weeks; refilling stores takes about 3 months of therapy.
Why can serum ferritin be normal in a patient with iron deficiency and active infection?
Ferritin rises with inflammation, liver damage and malignancy, so a 'normal' ferritin may hide iron deficiency. Many guidelines use a higher cut-off (e.g. <100 µg/L) when inflammation is present.
On a Wright-stained smear, red cells are bright orange-red and white cell nuclei are pale and poorly stained. The most likely cause is:
An acidic buffer favors the eosin dye, giving red cells a bright red color and weak nuclear staining. An alkaline buffer or overstaining makes the whole smear too blue.
Many round red cells without central pallor are seen only at the extreme feathered edge of an otherwise normal smear. The best interpretation is:
Cells at the feathered edge are flattened and lose central pallor, mimicking spherocytes. True spherocytes are seen throughout the proper reading area.
A patient returned from a tick-infested area of the northeastern USA with fever and hemolysis. The smear shows small rings, some in tetrads ('Maltese cross'), with no pigment. The most likely organism is:
Babesia forms tetrads and lacks hemozoin pigment and gametocytes, and is transmitted by Ixodes ticks. P. falciparum shows small rings too but has banana-shaped gametocytes and no tetrads.
Multifocal dense aggregates of spindle-shaped mast cells in marrow, aberrant CD25 expression and serum tryptase above 20 ng/mL point to systemic mastocytosis. Which mutation is typical?
KIT D816V is found in most adults with systemic mastocytosis and is a diagnostic criterion. JAK2 and MPL mutations drive classic MPNs.
In AML with a normal karyotype, which mutation is linked to a higher relapse risk and is a target for specific kinase inhibitors?
FLT3-ITD is associated with a higher relapse risk and is targeted by FLT3 inhibitors such as midostaurin, gilteritinib and quizartinib; under ELN 2022 it is classed as intermediate risk regardless of allelic ratio. NPM1 mutation without FLT3-ITD and in-frame bZIP CEBPA mutations are favorable, and IDH2 is targeted by an IDH inhibitor, not a kinase inhibitor.
A 2-year-old with Down syndrome has blasts with cytoplasmic blebs, MPO negative, and marrow fibrosis. Flow cytometry is likely to show positivity for:
This is acute megakaryoblastic leukemia, common in young children with Down syndrome; blasts express platelet glycoproteins CD41 (GPIIb) and CD61 (GPIIIa). CD14/CD64 indicate monocytic lineage.
Flow cytometry of marrow from a myeloma patient would most likely show clonal plasma cells with which pattern?
Neoplastic plasma cells usually lose CD19 and aberrantly express CD56. Normal plasma cells are CD19+ and CD56-negative.
An uncorrected WBC count is 15.0 × 10^9/L. The differential shows 25 NRBCs per 100 WBCs. The corrected WBC count is:
Corrected WBC = uncorrected WBC × 100/(100 + NRBC) = 15.0 × 100/125 = 12.0 × 10^9/L. Subtracting 25% (11.3) is a common error.
A healthy adult has mild thrombocytopenia, giant platelets and pale-blue Döhle-like inclusions in neutrophils. Which gene is involved?
May-Hegglin anomaly is an MYH9-related disorder with Döhle-like inclusions and giant platelets. LBR causes Pelger-Huët anomaly.
Plasma cells filled with multiple round pink-to-blue globules (Mott cells) contain:
Russell bodies are immunoglobulin stored in dilated rough endoplasmic reticulum; many such globules form a Mott cell. They are not phagocytic material.
Döhle bodies seen in neutrophils during infection are composed of:
Döhle bodies are pale-blue patches of rough ER/rRNA. Aggregated primary granules would appear as toxic granulation, not Döhle bodies.
An EDTA sample left 30 hours at room temperature is smeared. Neutrophils show vacuoles and nuclear swelling, but the patient is well. The best interpretation is:
Prolonged EDTA storage causes cytoplasmic vacuolation, crenation and nuclear changes. Smears should be made within a few hours of collection.
A healthy 2-year-old has a WBC of 10 × 10^9/L with 60% lymphocytes. The best interpretation is:
Young children normally have lymphocyte predominance, with neutrophils becoming dominant after about age 4–5. Adult ranges should not be applied.
A healthy adult of West African descent has a stable neutrophil count of 1.2 × 10^9/L, no infections and a normal marrow. Which red cell phenotype is commonly associated?
Duffy-null-associated neutrophil count (ACKR1 variant) causes a benign lower neutrophil count. It needs no treatment and should not be confused with pathologic neutropenia.
A smear fixed with a spray fixative containing polyethylene glycol arrives in the lab. Before Pap staining, the slide should be:
The waxy polyethylene glycol coating must be dissolved (e.g., soaking in 95% alcohol) before staining, otherwise stain uptake is poor.
During rapid on-site evaluation of a fine-needle aspiration, one set of smears is air-dried. Which stain is appropriate for these slides?
Air-dried smears are stained with Romanowsky-type stains, which are quick and show cytoplasm and background well. Pap stain requires wet alcohol fixation.
Brown-black, birefringent granules are seen across a bloody spleen section fixed in unbuffered formalin. How could this artifact have been prevented?
This is acid formaldehyde hematin (formalin pigment), which forms when acidic formalin reacts with hemoglobin. Buffering to neutral pH prevents it; alcoholic picric acid removes it.
Which method gives the most accurate determination of the end point of decalcification?
Radiography shows remaining calcium most accurately. The chemical ammonium oxalate test is also acceptable, while physical probing damages tissue and is unreliable.