MLT GlobeQCHP exam preparation (Qatar) – page 16
749 practice MCQs for the QCHP medical laboratory exam. Level: Intermediate.
Vitamin B12 is found naturally almost only in which foods?
Vitamin B12 is made by bacteria and enters the diet through animal products such as meat, eggs and milk. Strict vegans are at risk of deficiency.
Aminoglycoside antibiotics such as gentamicin are monitored mainly to avoid damage to which organs?
Aminoglycosides are nephrotoxic and ototoxic, and the risk rises with high trough levels, so peak and trough levels are monitored.
A large paracetamol (acetaminophen) overdose mainly damages which organ?
Excess paracetamol produces the toxic metabolite NAPQI, which causes hepatocellular necrosis, often with very high ALT a few days after ingestion.
Which tissue cell releases histamine when IgE bound to its surface is cross-linked by antigen?
Mast cells carry high-affinity IgE receptors. Cross-linking of bound IgE by allergen causes degranulation and release of histamine and other mediators.
Which of these is a secondary (peripheral) lymphoid organ?
Lymph nodes, spleen and mucosa-associated lymphoid tissue are secondary lymphoid organs where immune responses start. Thymus and bone marrow are primary lymphoid organs where lymphocytes develop.
The resident macrophages of the brain and spinal cord are called:
Microglia are the tissue macrophages of the central nervous system. Kupffer cells are in the liver, osteoclasts in bone and Langerhans cells in the epidermis.
ELISA stands for:
ELISA is enzyme-linked immunosorbent assay, in which an enzyme label on an antibody or antigen produces a measurable colour change.
Why are positive and negative controls included with each run of a serological test?
Controls with known reactivity show that reagents and procedure are working. If controls fail, patient results cannot be reported.
In HIV testing, the 'window period' is the time between:
During the window period the person is infected (and can transmit infection) but antibodies or antigen are not yet detectable, so a test may be falsely negative.
Multiple sclerosis is an autoimmune disease that damages:
In multiple sclerosis, immune attack on central nervous system myelin causes demyelinating plaques. CSF often shows oligoclonal IgG bands.
For kidney transplantation, matching is traditionally most important at which HLA loci?
HLA-A, -B and -DR are the loci classically considered in kidney matching; mismatches at these loci have the greatest effect on graft survival.
How is a person's HLA inherited?
HLA genes are inherited as haplotypes, one from each parent, and both are expressed. This is why siblings have a 25% chance of being HLA-identical.
Which urine specimen is preferred for routine culture from an adult who can collect it?
A clean-catch midstream sample reduces contamination by urethral and skin flora; bag urine and first-void drops are heavily contaminated.
Partial haemolysis with a greenish zone around colonies on blood agar is called:
Alpha haemolysis is incomplete lysis giving green discolouration; beta is complete clearing, and gamma means no haemolysis.
In a disk diffusion test, a larger zone of inhibition around an antibiotic disk generally means the organism is:
The drug diffuses outward from the disk; the more susceptible the organism, the wider the area in which it cannot grow.
Blood cultures should ideally be collected at what point in patient care?
Antibiotics already in the blood can prevent organisms from growing in the bottles, so cultures should be drawn before therapy begins.
Which bacterium is the most common cause of community-acquired lobar pneumonia?
The pneumococcus is the classic and most frequent cause of community-acquired lobar pneumonia.
Which organism is a leading cause of sepsis and meningitis in newborns during the first week of life?
Group B streptococci colonise the maternal genital tract and are a major cause of early-onset neonatal sepsis and meningitis.
A raised antistreptolysin O (ASO) titre supports recent infection with:
Streptolysin O is produced by group A streptococci, so a raised ASO titre supports recent S. pyogenes infection, for example before rheumatic fever.
Anthrax is primarily a disease of which animals, passing to humans by contact with them or their products?
Anthrax is a zoonosis of herbivores that eat spores from soil; humans are infected from animals, hides, wool or meat.