MLT GlobeSCFHS exam preparation (Saudi Arabia) – page 5
749 practice MCQs for the SCFHS medical laboratory exam. Level: Intermediate.
A 4-year-old has bloody diarrhea, then acute kidney injury, schistocytes and thrombocytopenia. The most likely cause is:
Typical hemolytic uremic syndrome in children follows STEC (e.g. O157:H7) infection. ADAMTS13 is usually normal in HUS.
Under high shear in arterioles, the first step of platelet adhesion to exposed collagen depends on:
Adhesion at high shear needs VWF to link collagen to platelet GPIb. GPIIb/IIIa–fibrinogen mediates the later aggregation step.
A fisherman who often eats raw freshwater fish develops macrocytic anemia with hypersegmented neutrophils. Which parasite is the likely cause?
The fish tapeworm Diphyllobothrium latum competes for vitamin B12 in the gut and can cause B12 deficiency. Hookworm (Necator) causes blood loss and microcytic iron deficiency instead.
Which drug most commonly causes megaloblastic change by inhibiting dihydrofolate reductase?
Methotrexate blocks dihydrofolate reductase, reducing active folate and DNA synthesis. Proton-pump inhibitors can reduce B12 absorption over years, but they do not act on folate metabolism.
Heinz bodies are best demonstrated by:
Heinz bodies are denatured, precipitated hemoglobin that is not visible on routine Romanowsky stains; supravital dyes such as crystal violet or brilliant cresyl blue show them. Prussian blue detects iron, not denatured hemoglobin.
A child with fat malabsorption and ataxia has red cells with a few irregular, unevenly spaced spiky projections and no central pallor. These cells are:
Acanthocytes have 2–20 irregular projections of different lengths and are typical of abetalipoproteinemia. Echinocytes have short, evenly spaced projections around the whole cell.
Nucleated red cells in the peripheral blood of an adult usually indicate:
Nucleated red cells are normally found only in the marrow in adults; in the blood they suggest severe hemolysis, hypoxia, marrow infiltration or loss of splenic function. They are not produced by storage.
Follicular lymphoma is characteristically associated with which translocation?
t(14;18) places BCL2 under the IGH enhancer, blocking apoptosis. t(8;14) is Burkitt and t(2;5) is anaplastic large cell lymphoma.
A cell with an eccentric round nucleus, coarse 'clock-face' chromatin, deep blue cytoplasm and a pale area next to the nucleus is a:
Plasma cells have eccentric nuclei, clumped chromatin and a perinuclear hof (Golgi zone) in basophilic cytoplasm. Myelocytes contain granules and lack clock-face chromatin.
What is the recommended minimum ratio of fixative volume to tissue volume for routine formalin fixation?
A fixative-to-tissue ratio of about 15–20:1 ensures enough formaldehyde is available for complete fixation. Smaller volumes become depleted, causing poor fixation.
What is the correct order of steps in routine paraffin tissue processing after fixation?
Water is removed with graded alcohols, the alcohol is replaced by a clearing agent (e.g., xylene) that mixes with paraffin, then tissue is infiltrated and embedded.
Eosin stains cytoplasm pink because it is:
Eosin is an anionic acidic dye that binds to basic (positively charged) groups in cytoplasmic proteins and collagen, called acidophilic structures.
A kidney section stained with Congo red shows deposits that are salmon-pink under ordinary light. What finding under polarized light confirms amyloid?
Congo red-stained amyloid shows apple-green birefringence with polarized light because of its beta-pleated sheet structure. Color alone is not specific.
Antimitochondrial antibody (M2 subtype) is a highly specific marker for:
AMA-M2 against the pyruvate dehydrogenase complex is found in about 95% of primary biliary cholangitis. Primary sclerosing cholangitis is associated with atypical p-ANCA.
Antibodies that stimulate the TSH receptor and cause hyperthyroidism are characteristic of:
TSH-receptor stimulating antibodies (TRAb/TSI) mimic TSH and cause Graves disease. This is a type II (antibody-mediated, receptor-stimulating) mechanism. Hashimoto thyroiditis is associated with anti-TPO.
Which autoantibody is found in most patients with generalised myasthenia gravis?
About 85% of generalised myasthenia gravis have antibodies that block or destroy acetylcholine receptors. Anti-VGCC is linked to Lambert–Eaton syndrome and anti-aquaporin-4 to neuromyelitis optica.
A tuberculin skin test that becomes indurated 48–72 hours after injection is an example of:
Delayed-type (type IV) hypersensitivity is mediated by sensitised T cells and macrophages, not antibody, and peaks at 48–72 hours. Contact dermatitis is another example.
Human HLA genes are located on which chromosome?
The major histocompatibility complex is on the short arm of chromosome 6. Beta-2 microglobulin, the light chain of class I molecules, is encoded on chromosome 15.
Which immunoglobulin binds with high affinity to Fc receptors on mast cells and basophils?
IgE binds FcεRI on mast cells and basophils. Cross-linking by allergen triggers degranulation and histamine release, the basis of type I hypersensitivity.
Which cytokine is the main T-cell growth factor produced by activated T cells?
IL-2 drives proliferation of activated T cells (autocrine and paracrine). IL-5 acts on eosinophils and IL-10 is mainly anti-inflammatory.