MLT GlobeDHA exam preparation (Dubai) – page 4
700 practice MCQs for the DHA medical laboratory exam. Level: Basic to intermediate.
A film from an elderly patient shows many small mature lymphocytes and numerous 'smudge' cells. Which disorder is most likely?
CLL cells are fragile and rupture during spreading, forming smudge cells; their chromatin is clumped in a 'soccer-ball' pattern. AML shows blasts; mononucleosis shows reactive lymphocytes.
When monocytes leave the blood and settle in tissues, what do they become?
Monocytes mature into tissue macrophages that phagocytose and present antigen. Monoblasts are marrow precursors; mast cells come from a separate progenitor.
Which immunoglobulin class circulates mainly as a pentamer joined by a J chain?
Serum IgM is a pentamer, making it efficient at agglutination and complement activation. Secretory IgA is a dimer; IgG, IgE and IgD are monomers.
Histologically, blood is classified as which basic tissue type?
Blood is a specialized connective tissue: cells suspended in a fluid extracellular matrix (plasma), and derived from mesenchyme.
A person with blood group B normally has which antibody in plasma?
People make naturally occurring antibodies against the ABO antigen they lack; group B lacks A antigen and has anti-A. Group O has both anti-A and anti-B.
Normal adult HbA is made of which globin chain pair?
HbA is α2β2. α2δ2 is HbA2, α2γ2 is HbF and epsilon chains occur in embryonic hemoglobins.
A microcytic hypochromic blood picture with normal ferritin suggests which condition?
Thalassemias reduce globin synthesis, giving small pale cells despite normal iron stores. The other conditions are usually normocytic.
In which condition are megaloblasts found in the bone marrow?
Folate or B12 deficiency slows DNA synthesis, so nuclei lag behind cytoplasm, producing large megaloblasts. Aplastic marrow is hypocellular.
Where do the stem cells that give rise to both T and B lymphocytes originate?
Lymphoid progenitors arise from marrow stem cells. B cells mature in the marrow; T-cell precursors migrate to the thymus to mature.
In ABO typing, what does reverse (serum) grouping detect?
Reverse grouping tests patient plasma against known A1 and B cells to detect antibodies, confirming forward grouping, which detects antigens on red cells.
A patient with a high fever has leukocytosis, neutrophilia and toxic granulation. Which infection is most likely?
Acute bacterial infections typically raise neutrophils with a left shift and toxic changes. Viral infections usually cause lymphocytosis.
Which hormone, made mainly by the kidney, stimulates red cell production in the bone marrow?
Peritubular kidney cells release erythropoietin in response to hypoxia, stimulating erythroid progenitors. Thrombopoietin, made in the liver, drives platelet production.
At what temperature must whole blood and red cell units be stored?
Red cells are refrigerated at about 4 ± 2 °C to slow metabolism and bacterial growth. Platelets are kept at 20–24 °C; plasma is frozen.
The anticoagulant abbreviated EDTA stands for what?
EDTA (ethylenediaminetetraacetic acid), usually as the K2 salt, is the anticoagulant of choice for CBCs because it preserves cell morphology.
Which feature distinguishes a mature circulating red cell from a leukocyte?
Normoblasts extrude their nucleus in the marrow, so mature erythrocytes are anucleate. Adult red cells are made in marrow, not the spleen; phagocytosis and plug formation belong to leukocytes and platelets.
In the common pathway, the prothrombinase complex (factor Xa, factor Va, Ca2+ and phospholipid) cleaves prothrombin to yield:
Prothrombinase converts prothrombin (factor II) to thrombin, which then cleaves fibrinogen to fibrin. Plasmin is generated from plasminogen during fibrinolysis.
A transfusion recipient has an alloantibody against an antigen on the donor's red cells. Which reaction is this most likely to cause?
Antibodies to red cell antigens destroy donor red cells, causing hemolysis. Febrile reactions relate to leukocytes/cytokines, post-transfusion purpura to anti-HPA-1a, and TRALI to anti-HLA/HNA antibodies.
Which feature describes a normal blood basophil?
Basophils are under 1% of leukocytes and have coarse, water-soluble dark granules overlying a bilobed or irregular nucleus. Orange-red granules identify eosinophils.
In a healthy adult, arterial blood pH is normally held within:
Buffer systems, lungs and kidneys keep blood pH near 7.4. Values below 7.35 indicate acidemia and above 7.45 alkalemia.
Which infection is routinely screened for in donated blood because it is transmitted by transfusion?
Blood donations are screened for HBV, HCV, HIV and syphilis (and malaria where endemic). Tetanus, typhoid and tuberculosis are not routine transfusion-transmitted risks.