MLT GlobeMOH exam preparation (UAE) – page 6
700 practice MCQs for the MOH medical laboratory exam. Level: Basic to intermediate.
A healthy adult's mean cell hemoglobin (MCH) is expected to fall within about:
MCH = Hb ÷ RBC count, normally about 27–32 pg. Low values indicate hypochromia (iron deficiency, thalassemia); high values accompany macrocytosis.
The APTT evaluates which parts of the coagulation cascade?
APTT is prolonged by deficiencies of XII, XI, IX, VIII and the common factors. The PT covers the extrinsic (factor VII) and common pathways.
Which anemia is NOT microcytic?
Pernicious anemia causes B12 deficiency and a macrocytic megaloblastic anemia. The others impair heme or globin synthesis, producing small cells.
Which immunoglobulin class, bound to mast cells and eosinophils, mediates defense against helminths?
IgE binds Fc-epsilon receptors on mast cells and basophils and triggers eosinophil-mediated killing of worms. It also drives immediate allergic reactions.
Which leukemia is the most common in older adults in Western countries, usually after age 60?
CLL is the commonest adult leukemia in Western populations, with median age around 70. CML peaks in middle age; ALL is mainly a childhood disease.
Which condition would NOT be expected to raise the MCV?
Iron deficiency causes microcytosis. Folate and B12 deficiency produce macrocytes, and large reticulocytes can raise the MCV after hemorrhage or hemolysis.
The normal adult spleen weighs approximately:
A normal spleen weighs about 150–250 g and is not palpable. It must enlarge substantially, commonly to about twice normal size, before it can be felt below the costal margin.
Red cells lacking which blood group antigens (Fy(a−b−)) resist invasion by Plasmodium vivax?
P. vivax uses the Duffy glycoprotein (DARC) as its receptor; the Fy(a−b−) phenotype, common in West Africans, confers resistance.
The most important clinical use of HLA typing is:
HLA matching reduces graft rejection and graft-versus-host disease. It also helps select platelets for refractory patients, but transplantation is its principal use.
In a minor crossmatch, which two components are tested together?
The minor crossmatch looks for donor antibodies against the patient's cells. The major crossmatch (recipient plasma + donor cells) is the one routinely performed.
By international convention, monoclonal anti-A typing reagent is coloured:
Anti-A is tinted blue and anti-B yellow (acriflavine) so they cannot be confused; anti-D and anti-A,B are usually colourless.
A patient on long-term methyldopa develops anaemia. Which test confirms that his red cells are coated with antibody in vivo?
The DAT detects IgG or complement already bound to red cells, as in drug-induced immune haemolysis. The IAT detects free antibody in plasma.
What role does dextrose play in CPDA-1 anticoagulant-preservative?
Red cells rely on glycolysis; dextrose keeps ATP levels up during storage. Citrate chelates calcium and phosphate buffers pH.
Antibodies to Rh antigens (e.g., anti-D) are characteristically:
Rh antibodies arise after transfusion or pregnancy, are IgG, react best at 37 °C and usually need the antiglobulin phase.
Red cells suspended in SAGM additive solution have a maximum storage time of:
Saline-adenine-glucose-mannitol extends red cell shelf life to 42 days at 2–6 °C. CPDA-1 alone gives 35 days.
Which product is stored at −18 °C or colder with a shelf life of about 12 months?
Frozen plasma components (FFP and cryoprecipitate) keep for 12 months at ≤ −18 °C. Platelets and granulocytes are kept at room temperature, red cells at 2–6 °C.
An RhD-positive patient needs red cells. Which donors are suitable?
The D-positive recipient has no reason to form anti-D, so D-negative cells are safe too; they are saved for D-negative patients.
An O RhD-negative patient needs red cells. Which donor units are compatible?
Group O plasma contains anti-A and anti-B, so only O cells are compatible, and D-negative cells prevent anti-D formation.
A RhD-negative, unsensitised pregnant woman carries a RhD-positive fetus. What is given to prevent anti-D formation?
Anti-D at about 28 weeks and within 72 h of delivery clears fetal D-positive cells before the mother's immune system responds.
A wound isolate forms flat colonies with a metallic sheen, a grape-like odour and green diffusible pigment on nutrient agar. It is most likely:
Pseudomonas aeruginosa produces pyocyanin/pyoverdine (green pigment), a grape-like or corn-tortilla odour and often a metallic sheen. Salmonella and streptococci are non-pigmented.