MLT GlobeQCHP exam preparation (Qatar) – page 22
749 practice MCQs for the QCHP medical laboratory exam. Level: Intermediate.
During an ESR test the tube is accidentally left tilted a few degrees from vertical. The result will be:
Even a small tilt lets cells slide down the side of the tube and settle faster, raising the ESR noticeably. The tube must stand exactly vertical, free of vibration.
A flow cytometry screening test for hereditary spherocytosis uses eosin-5'-maleimide (EMA). A positive result for hereditary spherocytosis is shown by:
EMA binds mainly to band 3; spherocytes have less band 3 and membrane, so their fluorescence is reduced. Loss of CD59 is a feature of PNH, not hereditary spherocytosis.
A patient has moderate hemolytic anemia with many target cells and some red cells containing blunt, finger-like crystals. Electrophoresis shows two bands of about equal amounts in the S and C positions. The diagnosis is:
Roughly equal HbS and HbC with target cells and SC crystals is typical of HbSC disease. Sickle cell trait shows HbA and HbS, with no HbC band.
Red cells incubated with brilliant cresyl blue show many fine, evenly spread inclusions giving a 'golf ball' appearance. The patient most likely has:
HbH (beta-4 tetramers) is unstable and precipitates with brilliant cresyl blue as many small inclusions. This occurs when three of four alpha genes are lost; beta-thalassemia trait does not produce HbH.
A woman develops painful skin necrosis 3 days after starting warfarin without heparin cover. Which underlying deficiency is most likely?
Protein C falls quickly on warfarin, creating a temporary hypercoagulable state; hereditary protein C deficiency increases the risk of skin necrosis. Factor XII deficiency does not cause this.
A newborn has delayed bleeding from the umbilical stump. PT, aPTT, fibrinogen and platelets are normal. Which test should be done next?
Factor XIII cross-links fibrin after clotting, so its deficiency does not affect PT or aPTT. The clot dissolves in 5 M urea; a quantitative factor XIII assay is preferred.
A patient on warfarin for a recent DVT has low protein C and protein S activity. What is the best interpretation?
Warfarin lowers vitamin K–dependent proteins C and S, and acute thrombosis can also consume them. Testing should be repeated off warfarin (usually at least 2 weeks).
When thrombin binds thrombomodulin on endothelial cells, it mainly activates:
Thrombomodulin switches thrombin from procoagulant to anticoagulant action, activating protein C (and TAFI). Bound thrombin no longer clots fibrinogen efficiently.
A 3-day-old breast-fed baby who did not receive vitamin K at birth has GI bleeding. PT and aPTT are prolonged; platelets and fibrinogen are normal. The most likely cause is:
Newborns have low vitamin K stores and breast milk contains little vitamin K, so factors II, VII, IX and X fall. DIC would also lower platelets and fibrinogen.
An EDTA smear shows platelets arranged in rings around neutrophils, and the analyzer count is low. This phenomenon is:
Platelet satellitism is an in-vitro EDTA-dependent antibody effect causing platelets to adhere to neutrophils, producing false thrombocytopenia. A citrate sample usually corrects it.
Large platelets that look pale grey and nearly agranular on Wright stain, with mild thrombocytopenia and marrow fibrosis, suggest:
Gray platelet syndrome (NBEAL2) lacks alpha granules, giving grey platelets; released growth factors cause fibrosis. Wiskott-Aldrich platelets are small.
For a normocytic, normochromic sample, which set of results fails the 'rule of three' check and should be investigated?
The rule expects RBC × 3 ≈ Hb and Hb × 3 ≈ Hct (±3%). With RBC 3.5 and Hct 31%, Hb should be about 10.5 g/dL; 14.0 g/dL does not fit, suggesting an error such as lipemia.
In anemia of chronic inflammation, raised hepcidin causes anemia mainly by:
IL-6 stimulates hepatic hepcidin, which binds and degrades ferroportin. Iron cannot leave macrophages or enterocytes, so serum iron falls despite adequate stores.
Which metabolite is raised in BOTH vitamin B12 deficiency and folate deficiency?
Both B12 and folate are needed to remethylate homocysteine to methionine, so homocysteine rises in either deficiency. Methylmalonic acid rises only in B12 deficiency.
A 62-year-old man is found to have iron deficiency anemia. He has no obvious bleeding. The most appropriate next step is to:
In adult men and post-menopausal women, iron deficiency is usually caused by chronic blood loss, most often from the gut, including colorectal cancer. Finding the cause is essential.
Small, irregular clusters of granules near the edge of some red cells on a Wright-stained smear are confirmed as Pappenheimer bodies when they:
Pappenheimer bodies contain iron and stain blue with Prussian blue; red cells with these iron granules are called siderocytes. Feulgen positivity indicates DNA, which is the feature of Howell-Jolly bodies.
In a patient with homozygous HbC, especially after splenectomy, the smear may show:
HbC is less soluble and can form dense, 'bar of gold' hexagonal crystals, together with many target cells. Golf ball inclusions are HbH precipitates in alpha-thalassemia.
A patient with severe burns shows small, dense spherical red cells and budding fragments. The mechanism is:
Heat above about 49°C damages spectrin, causing fragmentation and microspherocytes soon after the burn. The DAT is negative, so antibodies are not the cause.
The most common structural rearrangement in childhood B-ALL is often missed by routine karyotyping and has a favorable prognosis. It is:
ETV6::RUNX1 is cryptic on karyotype and needs FISH or PCR for detection; it carries a good outlook. BCR::ABL1 is uncommon in children and adverse.
What is the last stage of the neutrophil series that is still able to divide?
The myelocyte is the last stage capable of mitosis; from the metamyelocyte onward cells only mature. Promyelocytes also divide but are not the last dividing stage.