MLT GlobeDOH exam preparation (Abu Dhabi) – page 28
700 practice MCQs for the DOH medical laboratory exam. Level: Basic to intermediate.
Protozoa that ingest solid food particles by phagocytosis into food vacuoles show which type of nutrition?
Holozoic nutrition means taking in particulate food, as amoebae do with bacteria and red cells. Saprozoic nutrition means absorbing dissolved nutrients across the surface.
A patient's APTT is prolonged while the PT is normal. The defect most likely involves:
APTT assesses intrinsic and common pathways; isolated prolongation suggests factors XII, XI, IX or VIII. Factor VII deficiency prolongs PT alone.
A man with low serum testosterone has high LH and FSH. Where is the lesion?
Low testosterone with high gonadotrophins means the testes are not responding. Pituitary or hypothalamic disease gives low or inappropriately normal LH/FSH.
An adult has coarse facial features, enlarged hands and a deepening voice. Which test result confirms the likely diagnosis?
Acromegaly comes from GH excess, which thickens soft tissues including the larynx. It is confirmed by high IGF-1 and GH that does not suppress after oral glucose.
A patient on long-term steroids stops them suddenly and presents with hypotension, vomiting and hypoglycaemia. Which description fits this emergency?
Stopping steroids after HPA-axis suppression leaves too little cortisol, causing shock and hypoglycaemia. This is an adrenal (Addisonian) crisis, treated with IV hydrocortisone.
Which statement about multiple endocrine neoplasia (MEN) syndromes is correct?
MEN1 (MEN1 gene) and MEN2 (RET) are autosomal dominant and affect several endocrine glands. The type of tumour and degree of hormone rise vary.
Why is 24-hour urine free cortisol more useful than a single plasma total cortisol when screening for Cushing syndrome?
Total cortisol varies with time of day and CBG, which estrogens raise. UFC reflects unbound cortisol produced over 24 hours.
A neonate with ambiguous genitalia has low cortisol and very high 17-hydroxyprogesterone. What is the most likely diagnosis?
Blocked cortisol synthesis raises ACTH, and precursors are shunted to androgens. Cortisol is low despite obvious adrenal overactivity, so 17-OHP is the key test.
Hypercortisolism has been confirmed. Which test best separates ACTH-dependent causes from a primary adrenal tumour?
Suppressed ACTH points to an adrenal source, and normal or high ACTH to a pituitary or ectopic source. The other tests confirm hypercortisolism but do not localise it.
How can primary adrenal insufficiency be told apart from secondary (pituitary) insufficiency?
Adrenal failure removes feedback, so ACTH rises and causes pigmentation. In pituitary failure ACTH is inappropriately low.
A strongly positive serum gives a negative agglutination result when tested undiluted but positive results at higher dilutions. This is:
When antibody far exceeds antigen, each antigen site is covered by separate antibodies and lattices cannot form, giving a false negative. Testing serial dilutions reveals the true positive.
Narrow, septate hyphae with regular acute-angle (about 45°) branching in lung tissue suggest:
Aspergillus has narrow septate hyphae branching at acute angles. Mucorales have broad, ribbon-like, mostly aseptate hyphae with right-angle branching, which changes treatment.
Serum potassium is very high and calcium very low in a well patient. The most likely cause is:
K2EDTA adds potassium and chelates calcium. The correct order of draw (culture, citrate, serum, heparin, EDTA, fluoride) avoids this carryover.
During reverse typing, the supernatant in the B-cell tube is clear red and no cell button remains. How should this be interpreted?
ABO antibodies can activate complement and lyse reagent cells when serum is used. Hemolysis is a positive reaction and is recorded as such.
A donor reports receiving human pituitary-derived growth hormone as a child. What is the correct decision?
Pituitary-derived growth hormone has transmitted Creutzfeldt-Jakob disease, so recipients are deferred indefinitely. Recombinant growth hormone does not carry this risk.
Blood is needed for exchange transfusion of a newborn with anti-D HDFN. Which sample is preferred for antibody screening and crossmatch?
Maternal plasma has a higher antibody concentration and a larger volume, so incompatibility is easier to detect. Cord plasma can be used if a maternal sample is unavailable.
The S and s antigens are carried on which red cell membrane protein?
S, s and U are on glycophorin B. M and N are on glycophorin A, and Gerbich antigens are on glycophorins C and D.
An anti-E reacts 3+ with R2R2 cells but only 1+ with R1R2 cells. This pattern is best explained by:
R2R2 cells are homozygous for E (double dose) and carry more antigen than heterozygous R1R2 cells. Most Rh antigens except D show dosage.
Febrile non-hemolytic reactions to platelet transfusions are often caused by:
White cells in the bag release cytokines such as IL-1, IL-6 and TNF during room-temperature storage. Prestorage leukocyte reduction lowers these reactions.
A patient with a positive ANA has high-titre anti-U1-RNP as the only specific autoantibody, Raynaud phenomenon and swollen hands. The most likely diagnosis is:
A high titre of anti-U1-RNP is a defining feature of mixed connective tissue disease. Drug-induced lupus is associated with anti-histone antibodies.