BMAT Case Studies & Practical Application 3 — Questions and Answers
Question 1: A clinical case describes a child with recurrent infections, low immunoglobulin levels, and absent B-cells. Which condition does this most likely represent?
- DiGeorge syndrome
- X-linked agammaglobulinemia (Bruton's disease) (Correct answer)
- Chronic granulomatous disease
- Selective IgA deficiency
Correct answer: X-linked agammaglobulinemia (Bruton's disease)
X-linked agammaglobulinemia is characterized by absent B-cells and very low immunoglobulins due to a BTK gene mutation, leading to recurrent bacterial infections.
Question 2: A BMAT problem states that a car decelerates uniformly from 30 m/s to rest in 6 seconds. What is the magnitude of deceleration?
- 3 m/s²
- 4 m/s²
- 5 m/s² (Correct answer)
- 6 m/s²
Correct answer: 5 m/s²
Deceleration = change in velocity / time = 30/6 = 5 m/s².
Question 3: A patient is found to have a serum potassium of 6.8 mmol/L. Which ECG change is most likely to be seen?
- Prolonged QT interval
- Peaked T waves (Correct answer)
- ST depression
- Shortened PR interval
Correct answer: Peaked T waves
Hyperkalemia characteristically produces tall, peaked T waves on ECG, with worsening changes at higher levels including widened QRS and sine-wave pattern.
Question 4: A scientific paper claims that coffee consumption causes reduced Alzheimer's risk based on a survey study. What is the most important methodological limitation?
- The survey was conducted online
- Correlation cannot establish causation; confounding variables may explain the association (Correct answer)
- Alzheimer's is too rare to study
- The results would only apply to coffee drinkers
Correct answer: Correlation cannot establish causation; confounding variables may explain the association
Observational studies can identify associations but cannot prove causation due to potential confounders such as lifestyle, diet, or genetic factors.
Question 5: In a genetics case, two parents who are carriers of an autosomal recessive condition have a child. What is the probability that their next child will be an affected carrier?
- 25% (Correct answer)
- 50%
- 0% — carriers cannot be affected
- 75%
Correct answer: 25%
Each pregnancy from two carriers gives a 25% chance of an affected (homozygous recessive) child, independent of previous pregnancies.
Question 6: A hospital audit reveals that post-operative infection rates doubled after changing surgical glove suppliers. Which type of study would best confirm causation?
- Cross-sectional survey of surgeons
- Randomized controlled trial comparing glove types (Correct answer)
- Case series of infected patients
- Expert opinion review
Correct answer: Randomized controlled trial comparing glove types
A randomized controlled trial provides the strongest evidence for causation by controlling for confounders and allowing direct comparison.
Question 7: A chemistry scenario describes electrolysis of dilute sulfuric acid. What is produced at the cathode?
- Oxygen gas
- Sulfur dioxide
- Hydrogen gas (Correct answer)
- Sulfate ions
Correct answer: Hydrogen gas
During electrolysis of dilute sulfuric acid, hydrogen ions (H⁺) are reduced at the cathode to form hydrogen gas (H₂).
BMAT Case Studies & Practical Application 3
A clinical case describes a child with recurrent infections, low immunoglobulin levels, and absent B-cells.
Which condition does this most likely represent?