MLT GlobeASCP exam preparation (USA · MLS / MLT) – page 24
1200 practice MCQs for the ASCP medical laboratory exam. Level: Advanced.
A 22-year-old is admitted 2 days after a paracetamol (acetaminophen) overdose. ALT is 4500 U/L and AST 5200 U/L. This enzyme pattern indicates:
Aminotransferases above about 1000 U/L indicate massive hepatocyte necrosis, seen in toxic (paracetamol), ischemic or acute viral hepatitis. Cholestasis mainly raises ALP and GGT.
After heating serum at 56 °C for 10 minutes, most ALP activity remains. Which isoenzyme is most likely present?
Placental ALP is the most heat-stable isoenzyme; bone ALP is the most heat-labile ('bone burns'). Liver ALP is intermediate.
A child with swollen parotid glands has raised serum amylase and normal lipase. The amylase is mainly the:
Mumps parotitis releases salivary amylase; lipase is not produced by salivary glands, so it stays normal. Pancreatic amylase would usually rise together with lipase.
In SI units: total cholesterol 5.5 mmol/L, HDL 1.2 mmol/L, triglycerides 2.2 mmol/L. What is the Friedewald LDL cholesterol?
In mmol/L the VLDL term is TG/2.2, here 1.0. LDL = 5.5 − 1.2 − 1.0 = 3.3 mmol/L. Using TG/5 (0.44) wrongly gives about 3.9 mmol/L.
Which apolipoprotein is the main structural protein of LDL, with one molecule per particle?
Each VLDL, IDL and LDL particle carries one apo B-100, which binds the LDL receptor. Apo A-I is the main protein of HDL.
Lipoprotein(a) is best described as:
Lp(a) is LDL with apo(a), which resembles plasminogen, attached to apo B-100 by a disulfide bond. Its level is mainly genetic and is an independent cardiovascular risk factor.
A 12-year-old has LDL cholesterol of 290 mg/dL (7.5 mmol/L), normal triglycerides and tendon xanthomas; his father had an MI at 40. The defect most likely involves the:
This is familial hypercholesterolemia, usually from LDL receptor mutations, giving very high LDL with normal triglycerides (type IIa). LPL or apo C-II defects raise triglycerides.
A 55-year-old woman has new hypercholesterolemia with weight gain, cold intolerance and constipation. Which test should be done before starting lipid-lowering therapy?
Hypothyroidism reduces LDL receptor activity and is a common secondary cause of raised LDL; treating it may correct the lipids. Her symptoms point to thyroid, not adrenal disease.
Urobilinogen is formed from conjugated bilirubin by:
Gut bacteria deconjugate and reduce bilirubin to urobilinogen; part is reabsorbed and a small amount appears in urine. Broad-spectrum antibiotics can reduce its formation.
In the Jendrassik–Grof total bilirubin method, caffeine–sodium benzoate is added to:
Caffeine–benzoate acts as an accelerator, freeing unconjugated bilirubin so both fractions react with diazotized sulfanilic acid. Alkaline tartrate, not caffeine, shifts azobilirubin to the blue form.
The 'direct' bilirubin fraction measured by diazo methods without an accelerator consists mainly of:
Water-soluble conjugated bilirubin and albumin-bound delta bilirubin react directly with diazo reagent. Unconjugated bilirubin needs an accelerator and forms the 'indirect' fraction.
A 4-week-old infant has jaundice, pale stools and dark urine. Direct (conjugated) bilirubin is 4.0 mg/dL (68 µmol/L). Which diagnosis must be excluded urgently?
Conjugated bilirubin above 1.0 mg/dL (17 µmol/L) in an infant indicates cholestasis; biliary atresia must be excluded quickly because early surgery improves outcome. Breast milk and physiological jaundice are unconjugated.
A patient with acute viral hepatitis is most likely to show which laboratory pattern?
Hepatocellular injury impairs uptake, conjugation and excretion, so both bilirubin fractions rise; conjugated bilirubin enters urine, and ALT rises strongly. Isolated unconjugated rise suggests hemolysis or Gilbert syndrome.
Which handling is correct for a blood ammonia sample?
Ammonia rises in vitro from red cell metabolism and deamination of amino acids, so the sample should be put on ice and separated and tested quickly. Hemolysis and patient smoking also raise ammonia.
In the glutamate dehydrogenase method for ammonia, what is measured?
GLDH combines ammonia with 2-oxoglutarate to form glutamate while oxidizing NADPH; the fall in absorbance at 340 nm is proportional to ammonia. The indophenol (Berthelot) reaction is a different method.
A 7-year-old given aspirin during a viral illness develops vomiting and confusion. Ammonia and aminotransferases are high; bilirubin is near normal. The most likely diagnosis is:
Reye syndrome causes acute encephalopathy and fatty liver after aspirin use in viral illness, with high ammonia and aminotransferases but little or no jaundice. Hepatitis A usually causes clear jaundice.
Which test best reflects acute loss of hepatic synthetic function in fulminant liver failure?
Several clotting factors have half-lives of hours, so the PT/INR rises quickly when synthesis fails. Albumin has a half-life of about 3 weeks, so it falls slowly.
The Kjeldahl reference method converts measured nitrogen to protein using a factor of 6.25. This factor assumes that serum proteins contain on average:
Serum proteins average about 16% nitrogen by mass, so protein = nitrogen × 100/16 = nitrogen × 6.25. The factor itself is not the nitrogen percentage.
Transthyretin (prealbumin) is preferred over albumin for monitoring short-term nutritional support mainly because it:
Transthyretin's half-life of about 2 days lets it reflect recent changes, while albumin's half-life is about 3 weeks. Transthyretin is still lowered by inflammation, a key limitation.
Which serum marker is part of the International Staging System for multiple myeloma along with albumin?
The ISS uses serum beta-2 microglobulin and albumin; higher beta-2 microglobulin reflects tumour burden and renal function. The revised ISS adds LD and cytogenetics, not CRP.