MLT GlobeMOH exam preparation (UAE) – page 32
700 practice MCQs for the MOH medical laboratory exam. Level: Basic to intermediate.
In blood group serology, 'dosage' means that an antibody:
Homozygous cells (for example Jk(a+b−)) carry a double dose of antigen and react more strongly than heterozygous cells. This is typical of Kidd, Duffy, MNS and some Rh antibodies.
In an average adult without platelet consumption, one whole-blood-derived platelet unit is expected to raise the platelet count by about:
One whole-blood-derived unit raises the count in an average adult by about 5–10 × 10^9/L, which is why several units (or one apheresis unit) make up an adult dose.
Hydrops fetalis in severe HDFN results mainly from:
Severe fetal anemia causes high-output heart failure, and extramedullary hematopoiesis in the liver reduces protein synthesis. Together these cause generalized edema.
In serum protein electrophoresis at pH 8.6, what charge do most serum proteins carry and toward which electrode do they move?
At pH 8.6, above the isoelectric point of most serum proteins, they lose protons and become negatively charged, so they migrate toward the positive anode.
Which factor can raise serum urea without any change in kidney function?
More dietary protein means more amino acid nitrogen converted to urea. Liver failure and overhydration lower urea, and muscle mass affects creatinine rather than urea.
A toddler has swallowed many of his mother's iron tablets. Which laboratory test is most useful to assess the severity of poisoning?
Serum iron measured about 4–6 hours after ingestion is used to judge the severity of acute iron poisoning. Ferritin reflects stores and rises slowly.
A 2-month-old baby of an HIV-positive mother has a positive HIV antibody test. Why does this not confirm infection in the baby?
Maternal IgG crosses the placenta and can persist for up to 18 months, so infant diagnosis uses nucleic acid tests (HIV DNA or RNA) instead of antibody tests.
A young woman has a butterfly facial rash, joint pain, a positive ANA and anti-dsDNA antibodies. The most likely diagnosis is:
Malar rash, arthritis, a positive ANA and anti-dsDNA (highly specific) together strongly point to SLE.
In type III hypersensitivity, tissue damage is caused mainly by:
Immune complexes deposit in vessel walls, glomeruli and joints, activate complement and attract neutrophils, which cause the damage, as in serum sickness and lupus nephritis.
A non-diabetic patient with prolonged vomiting and poor food intake has positive urine ketones. The most likely reason is:
When carbohydrate intake is low, the body breaks down fat for energy and the liver produces ketone bodies, which appear in the urine even without diabetes.
CSF from a 5-day-old baby with meningitis shows Gram-positive cocci in chains. Which organism is most likely?
Group B streptococcus (S. agalactiae), acquired from the mother's genital tract, is a leading cause of neonatal meningitis and appears as Gram-positive cocci in chains.
On CHROMagar Candida, Candida albicans typically forms colonies that are:
The chromogenic medium gives green C. albicans colonies; C. tropicalis is blue and C. krusei pink and rough.
Histoplasma capsulatum is classically acquired by inhaling spores from soil contaminated with:
Histoplasmosis ('cave disease') follows inhalation of microconidia from soil rich in bat or bird guano.
In lactophenol cotton blue mounting fluid, the phenol component mainly:
Phenol kills the organism, lactic acid preserves structures and cotton blue stains the fungal wall.
The hepatitis B virus genome is best described as:
HBV (Hepadnaviridae) has a small, partially double-stranded circular DNA genome and replicates through an RNA intermediate.
Human herpesvirus 4 (HHV-4) is the formal name of:
HHV-1 and 2 are HSV, HHV-3 is VZV, HHV-4 is EBV and HHV-5 is CMV.
Why should the front air grille of a Class II biological safety cabinet not be blocked with papers or equipment?
Room air drawn in through the front grille forms the air curtain that keeps aerosols away from the operator.
What is the main difference between a calibrator and a control?
Calibrators have assigned values used to establish the measuring relationship; controls are run like patient samples to monitor performance.
On a Levey-Jennings chart, horizontal lines are usually drawn at:
The chart shows the target mean with SD limits so each control result can be judged against Westgard rules.
For coagulation tests, the correct ratio of blood to 3.2% sodium citrate in a light-blue tube is:
A 9:1 ratio is required; under-filling increases the relative citrate and falsely prolongs clotting times.