MLT GlobeDOH exam preparation (Abu Dhabi) – page 21
700 practice MCQs for the DOH medical laboratory exam. Level: Basic to intermediate.
A patient has calf pain when the foot is dorsiflexed (Homans' sign). Which test best rules out DVT when negative?
D-dimer is a fibrin degradation product with a high negative predictive value: a normal result in low-risk patients makes DVT unlikely. Homans' sign itself is unreliable.
A patient with aspirin intolerance needs antiplatelet therapy. Which drug, an ADP (P2Y12) receptor blocker, is a common alternative?
Clopidogrel blocks platelet P2Y12 receptors, a mechanism unrelated to cyclooxygenase. Ibuprofen is an NSAID that may cross-react; warfarin and heparin are anticoagulants.
After treatment for acute leukemia, which method is most sensitive for detecting minimal residual disease?
PCR can detect about one leukemic cell in 10^5–10^6 normal cells, far better than morphology or karyotyping, allowing early detection of relapse.
Which coagulation result is expected in hemophilia A?
Factor VIII is in the intrinsic pathway, so APTT is prolonged while PT, platelet count and platelet function are normal. Abnormal ristocetin aggregation suggests von Willebrand disease.
A CLL patient has lymphocytosis and a platelet count of 70 × 10^9/L, whether or not nodes or spleen are enlarged. What is the Rai stage?
Thrombocytopenia below 100 × 10^9/L defines Rai stage IV regardless of other findings; anemia with Hb below 11 g/dL defines stage III.
Elongated, pencil-shaped red cells on a film are a characteristic feature of which anemia?
Pencil (cigar) cells, a type of elliptocyte, are typical of iron deficiency, along with microcytic hypochromic cells. Sickle cells are crescent-shaped with pointed ends.
Which set of findings indicates intravascular hemolysis?
When red cells lyse inside vessels, free hemoglobin binds and depletes haptoglobin, then spills into urine; renal tubules store it as hemosiderin. LDH rises.
Which condition may lower the platelet count?
EBV infection can cause immune or splenic thrombocytopenia. Aspirin affects platelet function, not number; splenectomy and essential thrombocythemia raise counts.
By about what stage of fetal development does bone marrow become the main site of hematopoiesis?
Marrow hematopoiesis starts around the fourth to fifth month and becomes dominant by the end of the sixth month, overtaking the liver.
Charcot–Leyden crystals in the sputum of an asthmatic patient are derived from which cell?
Charcot–Leyden crystals form from galectin-10 in eosinophils, which increase in allergic conditions such as asthma.
What is the chain composition of HbA2?
HbA2 (α2δ2) is normally below 3.5% of adult hemoglobin and rises in β-thalassemia trait. α2β2 is HbA, α2γ2 is HbF and ζ2ε2 is Gower-1.
In which disorder does splenectomy usually cure the anemia, although the red cell defect remains?
Spherocytes are destroyed mainly in the spleen, so removing it stops most hemolysis even though spherocytes persist. It does not correct G6PD deficiency or thalassemia.
By WHO criteria, what hemoglobin level defines severe anemia in a non-pregnant adult?
WHO grades anemia in non-pregnant adults as mild, moderate (8.0–10.9 g/dL) and severe (below 8.0 g/dL). The cut-offs apply to any cause, including iron deficiency.
An RhD-negative person who has never been transfused or pregnant typically has which Rh antibody?
Unlike ABO antibodies, anti-D is not naturally occurring; it forms only after exposure to D-positive red cells through transfusion or pregnancy.
A child has palpable purpura on the buttocks and legs, abdominal pain and hematuria. What platelet count is expected?
Henoch–Schönlein purpura (IgA vasculitis) is a vascular purpura with a normal platelet count. Small platelets suggest Wiskott–Aldrich syndrome, prolonged clotting times DIC, and teardrop cells myelofibrosis.
Extramedullary hematopoiesis in the liver and spleen is LEAST expected in which situation?
Extramedullary hematopoiesis occurs physiologically in the fetus and when marrow is overwhelmed or fibrosed. In secondary polycythemia the normal marrow simply responds to erythropoietin.
The blue network seen in reticulocytes stained with new methylene blue represents precipitated:
Supravital dyes precipitate ribosomal RNA into a reticulum, giving reticulocytes their name. Denatured hemoglobin forms Heinz bodies; DNA fragments are Howell–Jolly bodies.
Raised serum iron with reduced TIBC and high transferrin saturation fits best with:
In sideroblastic anemia iron cannot be used for heme, so iron accumulates and TIBC falls. Iron deficiency raises TIBC; chronic inflammation lowers both iron and TIBC.
Massive splenomegaly WITHOUT significant lymph node enlargement is most characteristic of:
CML typically enlarges the spleen, often massively, while lymphadenopathy is uncommon. ALL, lymphoma and disseminated TB usually involve lymph nodes as well as liver and spleen.
Which complication is NOT typically associated with sickle cell anemia?
Sickling causes infarction of the renal medulla, bone infarcts prone to Salmonella infection and chronic anemia with cardiac strain. Pancreatitis is not a characteristic complication.