MLT GlobeQCHP exam preparation (Qatar) – page 2
749 practice MCQs for the QCHP medical laboratory exam. Level: Intermediate.
Kidney tubules, thyroid follicles and small gland ducts are lined by cells as tall as they are wide. This epithelium is:
A single layer of cube-shaped cells suits secretion and absorption in these sites; stratified cuboidal is confined to larger ducts.
A routine small biopsy in 10% NBF generally needs about how long for adequate fixation?
Formalin penetrates quickly but cross-linking takes hours; too short gives poor morphology, too long masks antigens.
Which organelle contains acid hydrolases for intracellular digestion?
Lysosomes are membrane-bound vesicles with hydrolytic enzymes active at acid pH. The Golgi packages these enzymes but does not carry out digestion.
The most widespread cartilage type in the body, found in articular surfaces, costal cartilages and the respiratory tract, is:
Hyaline cartilage is the most abundant, with a glassy matrix of type II collagen. Elastic and fibrocartilage occur at more limited sites.
A yellow-brown granular pigment accumulating with age in heart and liver cells, known as 'wear and tear' pigment, is:
Lipofuscin is an insoluble residue of lipid peroxidation in lysosomes. Hemosiderin is iron-positive with Perls'; melanin is bleached by oxidizers.
To distinguish collagen, muscle and fibrin in one section, a laboratory uses:
Trichrome methods use two or more acid dyes of different molecular size to colour collagen, muscle and fibrin differently.
CD68 immunostaining is used to identify:
CD68 is a lysosomal glycoprotein abundant in macrophages. Plasma cells are shown with CD138 and T cells with CD3.
Which cytochemical result best separates AML from ALL?
Myeloperoxidase (and Sudan black B) are positive in myeloblasts and negative in lymphoblasts. A threshold of 3% or more MPO-positive blasts supports a myeloid lineage.
Terminal deoxynucleotidyl transferase (TdT) in blasts is a marker of:
TdT is a DNA polymerase active in immature B and T lymphocytes. TdT-positive blasts support ALL or lymphoblastic lymphoma; mature lymphoid cancers such as CLL are TdT negative.
Why is only forward (cell) typing routinely done for ABO grouping of a newborn?
Infants begin producing their own ABO antibodies at about 3 to 6 months. Any antibodies present at birth come from the mother across the placenta, so reverse typing would not reflect the baby's group.
On MacConkey agar, which organism typically forms pink (lactose-fermenting) colonies?
Lactose fermentation produces acid, turning the neutral red indicator pink. E. coli ferments lactose quickly; Salmonella, Shigella and Proteus are non-fermenters and form colourless colonies. S. sonnei is a late fermenter.
Pear-shaped trophozoites with two nuclei and 'falling leaf' motility in a stool sample are:
Giardia trophozoites look like a face with two nuclei and have a sucking disc and four pairs of flagella. The cysts are oval with four nuclei.
The sickle cell mutation replaces which amino acid at position 6 of the beta-globin chain?
HbS results from glutamic acid → valine at beta-6. Glutamic acid → lysine at the same position gives HbC. The hydrophobic valine makes deoxygenated HbS polymerise and sickle the cell.
Toxic granulation, Döhle bodies and cytoplasmic vacuoles in neutrophils most suggest:
These are reactive changes in neutrophils during severe infection or inflammation. Vacuoles in particular suggest bacteremia.
Platelet concentrates are stored at:
Cold activates platelets and shortens their survival, so they are kept at room temperature and agitated for gas exchange. Shelf life is usually 5 days (up to 7 with bacterial testing), limited by the risk of bacterial growth.
The most widely used routine fixative in histopathology is:
10% NBF (about 4% formaldehyde) penetrates well and preserves morphology for H&E and most immunohistochemistry. Use at least 10 volumes of fixative per volume of tissue.
The Jaffe method for creatinine uses:
Creatinine reacts with picrate in alkaline solution to form a red-orange complex. Ketones, glucose and some cephalosporins also react and give false high results; enzymatic methods avoid this.
An encapsulated yeast seen with India ink in CSF of an HIV patient, which is urease positive, is:
Cryptococcus has a polysaccharide capsule that shows as a clear halo in India ink. Cryptococcal antigen testing of CSF or serum is more sensitive than India ink.
Which sugar, when added to H substance, gives the A antigen its specificity?
The A transferase adds N-acetyl-D-galactosamine to the H antigen. D-galactose is the immunodominant sugar of the B antigen.
The B gene product is a transferase that adds which sugar to the H antigen?
The B galactosyltransferase attaches D-galactose to the H structure. N-acetyl-D-galactosamine is added by the A transferase, not the B transferase.