MLT GlobeASCP exam preparation (USA · MLS / MLT) – page 49
1200 practice MCQs for the ASCP medical laboratory exam. Level: Advanced.
Which immunophenotype is typical of chronic lymphocytic leukemia?
CLL cells are B cells (CD19+) that co-express the T-cell marker CD5 and also CD23, with dim surface immunoglobulin. CD10 and TdT indicate B-lymphoblasts; CD11c, CD25 and CD103 indicate hairy cell leukemia.
Which peripheral blood finding most suggests a myelodysplastic syndrome?
MDS shows dysplasia; in neutrophils this is poor granulation and acquired bilobed nuclei (pseudo-Pelger-Huët). Hypersegmented neutrophils with macro-ovalocytes point to B12 or folate deficiency instead.
Giant platelets, thrombocytopenia and absent aggregation with ristocetin (not corrected by normal plasma) indicate:
Bernard-Soulier syndrome is a deficiency of the GP Ib-IX-V receptor for von Willebrand factor. Unlike von Willebrand disease, adding normal plasma does not fix ristocetin aggregation, because the defect is in the platelets.
Platelets that fail to aggregate with ADP, collagen and epinephrine but respond normally to ristocetin suggest:
GP IIb/IIIa binds fibrinogen to link platelets together, and every agonist except ristocetin needs it. Ristocetin agglutination depends on GP Ib and von Willebrand factor, which are normal.
Red cells type as group O and react only weakly with anti-H lectin. The plasma contains weak anti-H plus anti-A and anti-B, and saliva contains H substance. The best description is:
Para-Bombay people lack or have weak red-cell H (FUT1 inactive) but are secretors (FUT2 active), so H is present in saliva. Classical Bombay people have no H in saliva or on cells.
In a PEG antiglobulin test, the tubes are not centrifuged and read after the 37 °C incubation. Why?
PEG concentrates antibody by removing water, but spinning cells in PEG causes nonspecific clumping. Cells are washed and read only at the AHG phase.
A myeloma patient on daratumumab (anti-CD38) has all panel cells reactive at IAT. How is this interference usually removed?
DTT removes CD38 from reagent cells, so the drug no longer reacts. DTT also destroys Kell antigens, so K-negative units are usually given unless the patient is K-positive.
Warm autoantibodies in autoimmune hemolytic anemia most often show apparent specificity within which system?
Many warm autoantibodies react more strongly with cells carrying certain Rh antigens, such as e. The practical value is limited, but antigen-negative blood may be chosen in some cases.
A patient has anti-c and anti-K. About 20% of donors are c-negative and 91% are K-negative. About how many random units must be tested to find 2 compatible units?
Frequency of c−K− units = 0.20 × 0.91 = 0.182. Units needed = 2 ÷ 0.182 ≈ 11. Using only the c-negative frequency (10 units) underestimates the number.
A group A patient's immediate-spin crossmatches are incompatible with group A units. Her red cells do not react with Dolichos biflorus lectin, and her plasma agglutinates A1 cells. The best red cell choice is:
This A2 (or weak A subgroup) patient has anti-A1 reacting at room temperature. Group O red cells avoid the A1 antigen and are compatible.
In the United States, which donor screening test may be performed only once per donor rather than on every donation?
FDA allows a single negative test for T. cruzi (Chagas disease) antibody to qualify a donor for future donations. HIV, HBV and HCV markers are tested on every donation.
Why is hydroxyethyl starch (HES) added during granulocyte collection by apheresis?
HES causes red cell rouleaux and faster sedimentation, improving separation from granulocytes. Neutrophil release is increased by G-CSF or corticosteroids, not HES.
Red cells collected by intraoperative blood salvage and washed with saline are kept at room temperature. They must be transfused within:
Washed salvaged red cells held at 20–24 °C must be infused within 4 hours because of bacterial growth risk. If refrigerated within 4 hours, they may be kept up to 24 hours.
A double-volume exchange transfusion in a newborn removes approximately what fraction of the infant's original red cells?
Because incoming and outgoing blood mix, a double-volume exchange replaces about 85–90% of the infant's red cells. It removes only about half of the total bilirubin because of extravascular bilirubin.
A 3 kg term infant needs a double-volume exchange transfusion. Using a blood volume of 85 mL/kg, what volume is needed?
Blood volume = 3 × 85 = 255 mL. A double-volume exchange uses twice this, 510 mL.
A D-negative mother with sickle cell disease has a high fetal cell count by Kleihauer-Betke. Which method best confirms the fetal bleed?
Maternal F cells (raised HbF) resist acid elution and falsely raise KB counts. Flow cytometry separates fetal cells, which are HbF-positive and carbonic anhydrase-negative, from adult F cells.
Red cells that do NOT lyse when exposed to 2 M urea most likely have which phenotype?
The Kidd glycoprotein transports urea into the cell; normal cells swell and lyse in 2 M urea. Jk(a−b−) cells lack the transporter and resist lysis, making this a simple screening test for Kidd-null donors.
A donor has the dominant Lu(a−b−) phenotype caused by the In(Lu) gene (KLF1 variant). Which other antigen is typically weakened?
The In(Lu) type weakens Lutheran antigens and also depresses P1, i, AnWj and some Indian antigens. Kell, Duffy and Rh antigens are not affected.
The adult i phenotype (I-negative adult) in some Asian populations is associated with:
Some GCNT2 mutations that prevent I branching on red cells also affect the lens, so the Asian adult i phenotype is linked to congenital cataracts. CGD is linked to the McLeod phenotype.
A European donor's red cells type D+, C+, E−, c+, e+. What is the most probable Rh genotype?
Presence of C and c means one C and one c haplotype; E absent. The commonest combination is R1 (DCe) with r (dce). R0r' gives the same phenotype but is much rarer.