MLT GlobeSCFHS exam preparation (Saudi Arabia) – page 16
749 practice MCQs for the SCFHS medical laboratory exam. Level: Intermediate.
In acute hepatitis B infection, which serological marker is usually the first to appear?
HBsAg appears in blood first, often before symptoms. Anti-HBs appears late, after recovery or vaccination.
Which enzyme is commonly used as the label in ELISA tests?
Horseradish peroxidase and alkaline phosphatase are the most common ELISA labels; they convert a colourless substrate into a coloured product.
In a latex slide agglutination test for C-reactive protein, visible clumping indicates that:
The latex particles are coated with anti-CRP antibody. CRP in the serum cross-links the particles, producing visible agglutination, which is read as positive.
Celiac disease is an immune-mediated reaction triggered by which dietary component?
In celiac disease, gliadin from gluten in wheat, barley and rye triggers an immune response that damages the small-intestinal villi. Lactose intolerance is an enzyme deficiency, not an autoimmune disease.
The antinuclear antibody (ANA) test is used mainly as a screening test for:
A negative ANA makes SLE very unlikely, so it is the main screening test. Positive results are followed by tests for specific antibodies such as anti-dsDNA and anti-Sm.
Autoimmune hemolytic anemia, in which antibodies bind the patient's red cells, is which type of hypersensitivity?
In type II reactions antibody binds antigen on cell surfaces, leading to complement activation or phagocytosis of the cells, as in autoimmune hemolytic anemia.
Systemic lupus erythematosus occurs most often in:
SLE is about nine times more common in women than men and usually starts between puberty and menopause.
The LE cell, described in early lupus testing, is a neutrophil that has engulfed:
An LE cell is a phagocyte that has ingested nuclear material opsonised by antinuclear antibody. It has been replaced by ANA testing but explains the history of lupus serology.
Which virus is a major cause of infection after organ and stem cell transplantation and is often monitored by PCR?
Cytomegalovirus reactivation or transmission with the graft is a common and serious complication in transplant recipients, so CMV DNA is often monitored by quantitative PCR.
For culture of a deep wound infection, which specimen is generally best?
Aspirated pus or tissue contains the true pathogens in larger numbers, while surface swabs mainly pick up colonising skin flora.
Which of these antibiotics is a carbapenem?
Meropenem, imipenem and ertapenem are carbapenems; ceftriaxone is a cephalosporin, aztreonam a monobactam and amoxicillin a penicillin.
On a Gram-stained sputum smear, Streptococcus pneumoniae typically appears as:
Pneumococci are elongated, pointed (lancet-shaped) cocci in pairs, often with a capsule halo.
Enterococci are part of the normal flora mainly of the:
Enterococci are normal gut bacteria, which is why they cause urinary, abdominal and wound infections.
Cutaneous anthrax typically produces which lesion?
The 'malignant pustule' of cutaneous anthrax becomes a painless black necrotic eschar surrounded by oedema.
Respiratory diphtheria spreads from person to person mainly by:
C. diphtheriae is carried in the throat and spread by droplets and close contact.
Besides antibiotics, which treatment must be given promptly in respiratory diphtheria?
Antitoxin neutralises circulating toxin before it binds to cells; antibiotics alone do not neutralise toxin already formed.
Proteus mirabilis urinary infections can lead to kidney stones because the organism produces:
Urease splits urea to ammonia, making urine alkaline so that struvite stones form.
Which part of the Gram-negative outer membrane lipopolysaccharide is responsible for endotoxin effects such as fever and shock?
Lipid A is the toxic component of LPS; the O side chain is the antigenic part used in serotyping.
In the serotyping of Enterobacterales, the flagellar antigen is designated:
H antigens are flagellar proteins; O is the somatic LPS antigen and K (including Vi) are capsular antigens.
Bubonic plague caused by Yersinia pestis is transmitted to humans mainly by:
Fleas from infected rodents transmit Y. pestis; pneumonic plague can then spread person to person by droplets.