MLT GlobeASCP exam preparation (USA · MLS / MLT) – page 52
1200 practice MCQs for the ASCP medical laboratory exam. Level: Advanced.
Which test is regarded as the reference (gold standard) functional assay for heparin-induced thrombocytopenia?
The washed-platelet serotonin release assay shows platelet activation by patient antibodies and is highly specific. The ELISA is sensitive but gives many false positives.
A patient with chronic inflammation is also anemic. Which result best suggests coexisting iron deficiency?
Soluble transferrin receptor rises when erythroid cells lack iron but is not an acute-phase reactant, so it stays normal in pure anemia of chronic disease. Ferritin rises with inflammation and can hide iron deficiency.
Reticulocyte hemoglobin content (CHr or Ret-He) is useful because it reflects:
Reticulocytes circulate for only 1–2 days, so their hemoglobin content shows current iron supply to the marrow. It falls early in iron deficiency and rises within days of effective iron therapy.
Ring sideroblasts are defined on a Prussian blue-stained marrow as erythroblasts with:
ICSH/WHO define a ring sideroblast as an erythroblast with ≥5 siderotic granules covering at least a third of the nuclear circumference. These granules are iron-loaded mitochondria.
Red cells with a slit-like area of central pallor are a typical finding in which blood group-related condition?
Absence of Rh proteins disturbs the membrane and produces stomatocytes with mild hemolysis. The McLeod phenotype is associated with acanthocytes, not stomatocytes.
A man has hemolytic anemia with marked coarse basophilic stippling. His blood lead level is normal. The most likely inherited enzyme defect is:
Pyrimidine 5'-nucleotidase normally breaks down ribosomal RNA; its deficiency leaves aggregated ribosomes visible as stippling. Lead also inhibits this enzyme, which explains stippling in lead poisoning.
According to ICSH recommendations, schistocytes in an adult smear provide strong morphological support for thrombotic microangiopathy when they exceed:
ICSH suggests that a schistocyte count above 1% in adults is a robust indicator of TMA when the clinical picture fits. Small numbers (under about 0.5%) can be seen in healthy people and many other conditions.
According to the WHO 5th edition, persistent monocytosis for a diagnosis of chronic myelomonocytic leukemia requires monocytes of at least:
WHO 5th lowered the absolute threshold to ≥0.5 × 10^9/L, with monocytes ≥10% of the WBC. The older threshold was 1.0 × 10^9/L.
Under the WHO 5th edition, which abnormality allows a diagnosis of AML even when blasts are below 20%?
WHO 5th removed the 20% blast requirement for AML with defining genetic abnormalities such as NPM1, except BCR::ABL1 and CEBPA types, which still need ≥20%. FLT3-ITD is not a defining abnormality.
A 4-month-old infant has B-ALL with WBC 250 × 10^9/L, CD10-negative blasts and t(4;11)(q21;q23). This finding indicates:
t(4;11) gives KMT2A::AFF1, common in infant ALL; blasts are usually CD10-negative and the outlook is poor. ETV6::RUNX1 and hyperdiploidy are favorable in older children.
A smear shows heavy dark granules in neutrophils. Which finding favors Alder-Reilly anomaly over toxic granulation?
Alder-Reilly granules appear in all leukocytes and persist without infection. Döhle bodies, vacuoles and a left shift accompany toxic granulation in sepsis.
Inherited Pelger-Huët anomaly results from a mutation in the gene for:
Pelger-Huët anomaly is caused by LBR (lamin B receptor) mutations, which impair nuclear segmentation. MYH9 relates to May-Hegglin anomaly.
Many smudge cells prevent an accurate differential in a CLL patient. What step can reduce them?
Mixing blood with albumin stabilizes fragile lymphocyte membranes and reduces smudging. Delay would increase cell damage.
An ANA test is positive at 1:80 with a speckled pattern in an otherwise healthy 60-year-old woman. The best interpretation is:
Low-titre ANA is found in a significant proportion of healthy people, more often in older women. ANA is a sensitive screening test and must be interpreted with clinical findings and specific antibody tests.
Antibody specificities that differ because of unique variable-region structures of a particular antibody are called:
Idiotypes are unique determinants in the variable region of a given antibody. Isotypes are class differences (e.g. IgG vs IgM); allotypes are inherited variants between individuals of the same species.
Th17 cells mainly protect against extracellular bacteria and fungi by producing IL-17, which recruits:
IL-17 induces chemokines that recruit neutrophils to mucosal and skin sites. Th2 cells, not Th17, drive eosinophil responses through IL-5.
A kappa:lambda free light chain ratio in serum is used mainly to detect:
Each B-cell clone makes only one light chain type. A clonal plasma cell disorder produces excess of one type, giving an abnormal kappa:lambda ratio.
A newborn screening TREC (T-cell receptor excision circle) assay result is undetectable. This suggests:
TRECs are DNA circles formed during T-cell receptor rearrangement in new thymic emigrants. Absent TRECs show very few new T cells, typical of SCID.
In a kinetic assay, NADH (molar absorptivity 6220 L·mol⁻¹·cm⁻¹) gives an absorbance of 0.311 in a 1 cm cuvette. The NADH concentration is:
c = A/(εb) = 0.311/(6220 × 1) = 5.0 × 10⁻⁵ mol/L = 50 µmol/L. Check the power of ten carefully when converting to µmol/L.
Concentrated hydrochloric acid is 37% (w/w) HCl with a specific gravity of 1.19. Given MW 36.5 g/mol, its approximate molarity is:
Molarity = (SG × 1000 × % purity)/MW = (1.19 × 1000 × 0.37)/36.5 ≈ 12.1 mol/L. Forgetting the specific gravity gives 10.1 mol/L.