MLT GlobeMOH exam preparation (UAE) – page 5
700 practice MCQs for the MOH medical laboratory exam. Level: Basic to intermediate.
A boy develops acute hemolysis with bite cells after eating fava beans. Which enzyme deficiency is most likely?
G6PD deficiency leaves red cells unable to generate NADPH, so oxidants in fava beans cause hemolysis (favism). It also causes neonatal jaundice.
Which anticoagulant is used for routine PT and APTT testing?
Citrate binds calcium reversibly, and adding calcium in the assay restarts clotting. Blood-to-citrate ratio must be 9:1. Heparin inhibits clotting factors; EDTA is for CBCs.
A prolonged prothrombin time mainly reflects a problem in which part of coagulation?
PT tests factor VII (extrinsic) plus X, V, II and fibrinogen (common). APTT tests the intrinsic and common pathways.
The JAK2 V617F mutation is found in more than 95% of patients with which disorder?
JAK2 V617F or exon 12 mutations are found in nearly all PV cases and in about half of ET and PMF. CML is defined by BCR::ABL1.
How does EDTA prevent blood from clotting?
EDTA binds calcium irreversibly, and calcium is needed at several coagulation steps. This is why EDTA samples cannot be used for clotting tests.
A mesh of fibrin strands trapping red cells and platelets is known as what?
Thrombin turns fibrinogen into fibrin, which traps cells to form a clot. Plaque is an atheromatous lesion; rouleaux are stacked red cells.
How many β-globin chains does fetal hemoglobin (HbF) contain?
HbF is α2γ2, with gamma chains in place of beta chains. This is why β-thalassemia and sickle cell disease are silent before birth.
Platelets are released into the blood as cytoplasmic fragments of which bone marrow cell?
Megakaryocytes extend proplatelet processes into marrow sinusoids and shed platelets. Osteoclasts are also large marrow cells but resorb bone and derive from monocytes.
A woman with long-standing heavy menstrual loss would most likely show which red cell appearance on the smear?
Chronic blood loss causes iron deficiency, reducing hemoglobin synthesis and producing microcytic hypochromic cells, often with pencil cells. Microspherocytes suggest spherocytosis or immune hemolysis.
The disorder described by Thomas Cooley, presenting in infancy with severe transfusion-dependent anemia and bone changes, is:
Cooley's anemia is homozygous or compound heterozygous β-thalassemia with severe ineffective erythropoiesis, marrow expansion and lifelong transfusion need.
A 4-year-old presents with pallor, bruising and bone pain, and blasts are seen on the smear. Statistically, the most likely diagnosis is:
ALL is the commonest childhood cancer, peaking at 2–5 years, mostly of B-cell type. AML is more common in adults, and CLL essentially does not occur in children.
Romanowsky stains combine methylene blue/azure dyes with eosin. Which stain does NOT belong to this group?
Giemsa, Wright and Leishman are Romanowsky stains producing the purple nuclear effect. Hematoxylin is a mordant nuclear dye used in H&E and Pap staining.
Marrow failure after high-dose exposure to ionizing radiation typically produces:
Radiation kills dividing hematopoietic stem and progenitor cells, leaving a hypocellular marrow and pancytopenia. It does not cause iron-deficient or megaloblastic changes.
Which feature identifies a mature segmented neutrophil on a Wright-stained smear?
Neutrophils have a segmented nucleus and fine lilac granules and form about 40–75% of adult leukocytes. Metachromatic granules suggest basophils; agranular blue cytoplasm suggests lymphocytes.
Which hemoglobin pattern is expected in a healthy adult?
Adults have over 95% HbA, HbA2 below about 3.5% and HbF below 1–2%. High HbF is normal at birth; 40% HbS indicates sickle cell trait.
Light-blue-top tubes for coagulation testing contain 3.2% sodium citrate, which prevents clotting by:
Citrate forms a soluble complex with calcium, reversibly; adding calcium back in the test restarts clotting. Heparin, not citrate, acts through antithrombin.
Which feature identifies an eosinophil on a Romanowsky-stained smear?
Eosinophils have acidophilic granules staining with eosin and a bilobed nucleus; they are about 1–6% of leukocytes. Dark purple masking granules indicate basophils.
Which procedure is a bleeding-time test rather than a method for measuring hemoglobin?
Ivy's method measures bleeding time from a standardized forearm incision. The other three convert hemoglobin to a colored derivative read photometrically or visually.
Hemoglobin HPLC in homozygous sickle cell disease shows predominantly:
In HbSS there is no HbA; HbS makes up most hemoglobin with variable HbF and normal HbA2. HbH (β4) belongs to α-thalassemia.
Besides hereditary spherocytosis, numerous spherocytes on a blood film are typical of:
IgG-coated red cells lose membrane to splenic macrophages and become spherocytes. The DAT separates immune from hereditary spherocytosis.