MLT GlobeSCFHS exam preparation (Saudi Arabia) – page 8
749 practice MCQs for the SCFHS medical laboratory exam. Level: Intermediate.
One 300 µg dose of RhIG protects against a fetal bleed of about:
A standard 300 µg dose covers about 30 mL of fetal whole blood, which is about 15 mL of fetal red cells.
The Leb antigen on gastric mucosa is a binding site for:
H. pylori attaches to Leb on gastric epithelium. P. vivax uses Duffy and parvovirus B19 uses the P antigen.
In Wiener notation, the haplotype r′ corresponds to:
Lower-case r means D-negative; the prime (′) indicates C. So r′ is dCe, while r″ is dcE and ry is dCE.
Testing cell-free fetal DNA in maternal plasma for RHD is used mainly to:
Non-invasive fetal RHD genotyping avoids unnecessary RhIG when the fetus is D-negative and helps manage immunized women.
The first D-positive baby of a previously unsensitized D-negative woman is usually not affected by anti-D HDFN because:
Most fetal bleeds large enough to immunize happen at delivery, and a primary response makes little IgG. Later D-positive pregnancies trigger a strong secondary IgG response.
Before collecting an arterial sample from the radial artery, the modified Allen test is performed to check:
The Allen test confirms that the ulnar artery can supply the hand if the radial artery is damaged or blocked by the puncture. It does not assess blood pressure or coagulation.
Which hormone is the principal hormone that lowers blood glucose concentration?
Insulin increases glucose uptake by muscle and fat and promotes glycogen synthesis. Glucagon, cortisol and growth hormone are counter-regulatory hormones that raise glucose.
For most non-pregnant adults with diabetes, the ADA recommends an HbA1c goal of less than:
The general ADA target is below 7% (53 mmol/mol), made stricter or looser for individual patients. 6.5% is the diagnostic cut-off, not the treatment goal.
Which ion is the main cation inside body cells?
About 98% of body potassium is intracellular, where its concentration is near 150 mmol/L. Sodium is the main extracellular cation.
Which dye is commonly used in automated photometric methods for total serum calcium?
Arsenazo III (and o-cresolphthalein complexone) forms colored complexes with calcium. Bromocresol green is used for albumin and ferrozine for iron.
In a healthy person with a normal sleep pattern, serum cortisol is highest:
Cortisol follows a circadian rhythm, peaking around waking and reaching its lowest level near midnight. This is why morning samples are used to assess adrenal insufficiency.
In an enzyme rate assay, the first seconds after mixing show a slow, non-linear change before a steady rate is reached. This period is called the:
During the lag phase, coupled reactions and temperature are still reaching steady state, so readings are not used. Activity is calculated only from the linear phase that follows.
A patient's total CK is 600 U/L the morning after an intramuscular injection; troponin is normal. The raised CK most likely comes from:
Intramuscular injections damage muscle fibers and release CK-MM, raising total CK for a few days. Normal troponin excludes myocardial injury.
Which lipid result is most affected if the patient ate a meal shortly before blood collection?
Dietary fat appears as chylomicron triglyceride within hours of a meal. Total cholesterol, HDL cholesterol and apo B change only slightly after eating.
Statins lower plasma cholesterol by inhibiting which enzyme?
HMG-CoA reductase is the rate-limiting enzyme of cholesterol synthesis. Less liver cholesterol increases LDL receptor expression, which lowers plasma LDL.
The primary bile acids synthesized by the liver from cholesterol are:
The liver makes cholic and chenodeoxycholic acids and conjugates them with glycine or taurine. Gut bacteria convert them to the secondary bile acids deoxycholic and lithocholic acid.
In a healthy term newborn, physiological jaundice typically peaks at:
Physiological unconjugated hyperbilirubinemia peaks around days 3–5 and settles within about 2 weeks in term babies. Jaundice in the first 24 hours is pathological.
Which enzyme converts biliverdin to bilirubin?
Heme oxygenase opens heme to biliverdin, and biliverdin reductase then reduces it to unconjugated bilirubin. UGT1A1 conjugates bilirubin in the liver.
A patient with advanced cirrhosis has low urea, normal creatinine and high ammonia. The low urea is best explained by:
The failing liver cannot convert ammonia to urea, so urea falls while ammonia rises. Kidney injury and dehydration raise urea, and a high-protein diet increases it.
What is the main physiological function of albumin?
Albumin is the most abundant plasma protein and provides about 80% of plasma oncotic pressure, holding water in the vessels. It also transports bilirubin, fatty acids, calcium and drugs.