MLT GlobeASCP exam preparation (USA · MLS / MLT) – page 35
1200 practice MCQs for the ASCP medical laboratory exam. Level: Advanced.
The Pk antigen (Gb3, CD77) is the cellular receptor for:
Gb3 (Pk) binds Shiga and Shiga-like toxins. Parvovirus B19 uses globoside, the P antigen.
An antibody gives small, shiny, refractile mixed-field agglutinates at AHG and is neutralized by guinea pig urine. The specificity is:
Anti-Sda gives refractile mixed-field agglutinates and is neutralized by guinea pig urine. Anti-Ch is neutralized by pooled plasma.
Unusually strong anti-P1 is associated with infection by:
Hydatid cyst fluid contains P1-like substance that boosts anti-P1. Mycoplasma is linked to anti-I and EBV to anti-i.
A donor of European descent types D+, C+, c+, E+, e+. The most probable genotype is:
All four genotypes give this phenotype, but R1 and R2 are the most common D-positive haplotypes, so R1R2 is by far the most probable.
Many monoclonal anti-D reagents are a blend of IgM and IgG. The IgG component is included to:
IgM gives direct agglutination at immediate spin; the IgG part allows the weak D test at the antiglobulin phase.
Weak D testing is not required for transfusion recipients. A recipient with weak D whose D test is negative at immediate spin will:
Such patients are simply treated as D-negative, which is safe. Weak D testing is required for donors and for newborns of D-negative mothers.
A patient has post-transfusion purpura with severe bleeding. Which treatment is first-line?
IVIG is first-line and usually raises the platelet count within days. Random platelets are usually destroyed quickly and give little benefit.
A suspected acute hemolytic reaction is investigated. The group O patient's post-transfusion sample shows mixed-field agglutination with anti-A. This suggests:
A mixed-field reaction with anti-A means two red cell populations: the patient's O cells and transfused A cells. This supports an ABO-incompatible transfusion, often due to misidentification.
A 40-year-old woman with normal anion gap metabolic acidosis, K 2.8 mmol/L and nephrocalcinosis cannot lower her urine pH below 6.0. The most likely diagnosis is:
Distal RTA is a failure to secrete H+ in the collecting duct, so urine pH stays above 5.5 despite acidosis, with hypokalemia and calcium stones. Type 4 RTA causes hyperkalemia.
Before capillary blood gas collection from a newborn's heel, the skin is warmed mainly to:
Warming the heel (to no more than about 42 °C) dilates vessels and "arterializes" the capillary blood. It does not replace antiseptic cleaning or anticoagulant in the tube.
What is the hydrogen ion concentration of plasma with a pH of 7.00?
pH = −log[H+]; pH 7.00 means [H+] = 10^−7 mol/L = 100 nmol/L. The normal value at pH 7.40 is about 40 nmol/L, so pH 7.00 means [H+] has more than doubled.
A non-pregnant adult has a 75 g OGTT: fasting glucose 92 mg/dL (5.1 mmol/L) and 2-hour glucose 165 mg/dL (9.2 mmol/L). By ADA criteria this is:
A 2-hour value of 140–199 mg/dL (7.8–11.0 mmol/L) defines impaired glucose tolerance (prediabetes). The fasting value is below 100 mg/dL, so it is not impaired fasting glucose.
A patient with diabetic ketoacidosis has Na 135, K 5.0, Cl 95 and HCO3 8 mmol/L. What is the anion gap, calculated as Na − (Cl + HCO3)?
135 − (95 + 8) = 32 mmol/L, a high anion gap caused by unmeasured ketoacid anions. 37 would be the result if potassium were wrongly added.
A peritoneal dialysis patient using icodextrin has a meter glucose of 250 mg/dL, while laboratory hexokinase glucose is 95 mg/dL. The meter most likely uses:
Icodextrin is metabolized to maltose. GDH-PQQ enzymes are not glucose-specific and react with maltose, giving dangerously high false readings. Glucose oxidase is specific for glucose.
In the enzymatic β-hydroxybutyrate assay, β-hydroxybutyrate dehydrogenase converts β-hydroxybutyrate to acetoacetate. What is measured?
The reaction uses NAD+ as coenzyme, so NADH is produced and the absorbance at 340 nm rises in proportion to β-hydroxybutyrate. Nitroprusside does not react with β-hydroxybutyrate.
An adult with chronic diarrhea and steatorrhea has low blood and urine D-xylose after an oral dose. Renal function is normal. This most suggests:
D-xylose is absorbed without needing pancreatic enzymes or bile, so poor absorption points to a mucosal problem (e.g., celiac disease). In pancreatic insufficiency the xylose test is normal.
A child has a sweat chloride of 72 mmol/L collected by pilocarpine iontophoresis. This result is:
Sweat chloride of 60 mmol/L or more is consistent with cystic fibrosis; 30–59 mmol/L is intermediate and below 30 mmol/L is unlikely. CF is caused by a defective CFTR chloride channel.
In the enzymatic method for serum bicarbonate (total CO2), which reaction is measured?
PEP carboxylase fixes HCO3− to form oxaloacetate, which malate dehydrogenase reduces while oxidizing NADH; the fall at 340 nm is proportional to bicarbonate. Hexokinase is used for glucose.
In many newborn screening programmes, which analyte in a dried heel-prick blood spot is used to detect congenital hypothyroidism?
Most programmes measure TSH (sometimes with T4) on dried blood spots; a high TSH suggests primary congenital hypothyroidism. Samples taken too early may show a physiological TSH surge.
On electrophoresis at pH 8.6, which creatine kinase isoenzyme moves fastest toward the anode?
CK-BB (CK-1) is the most negatively charged and moves furthest toward the anode, CK-MB is intermediate, and CK-MM (CK-3) stays nearest the cathode.