This focused MCQ set on “Diagnosis, treatment and disease control” integrates key research methodology and biostatistics concepts tailored for M.Pharm students. The questions target diagnostic test evaluation, therapeutic trial design, and measures used in disease control and surveillance. Emphasis is on practical interpretation—sensitivity, specificity, predictive values, likelihood ratios, ROC analysis, bias in diagnostic and screening studies, randomized trial principles, sample size considerations, and population-level control metrics such as incidence, R0 and herd immunity thresholds. These items will help strengthen critical appraisal skills for research papers, design decisions for diagnostic and interventional studies, and statistical reasoning needed in clinical pharmacology and public health pharmacy.
Q1. Which statistic indicates the proportion of true positives correctly identified by a diagnostic test?
- Sensitivity
- Specificity
- Positive predictive value
- Negative predictive value
Correct Answer: Sensitivity
Q2. In a diagnostic study, which design is least prone to spectrum bias when estimating test accuracy?
- Prospective cross-sectional study of consecutive patients referred for diagnosis
- Case-control study selecting clear cases and healthy controls
- Retrospective chart review of diseased patients only
- Enriching sample with extreme cases to increase event rate
Correct Answer: Prospective cross-sectional study of consecutive patients referred for diagnosis
Q3. What does an area under the ROC curve (AUC) of 0.5 imply about a diagnostic test?
- The test perfectly discriminates diseased from non-diseased
- The test performs no better than chance
- The test has high sensitivity but low specificity
- The test has high specificity but low sensitivity
Correct Answer: The test performs no better than chance
Q4. Which measure is calculated as sensitivity / (1 − specificity) and indicates how much a positive result increases the odds of disease?
- Positive likelihood ratio
- Negative likelihood ratio
- Diagnostic odds ratio
- Youden’s index
Correct Answer: Positive likelihood ratio
Q5. What is the primary bias introduced by using screening tests that preferentially detect slower-progressing disease?
- Lead-time bias
- Length-time bias
- Verification bias
- Observer bias
Correct Answer: Length-time bias
Q6. In randomized controlled trials of treatment efficacy, which analysis preserves allocation and provides conservative estimates of effectiveness in presence of noncompliance?
- Per-protocol analysis
- As-treated analysis
- Intention-to-treat analysis
- Per-protocol-with-adjustment analysis
Correct Answer: Intention-to-treat analysis
Q7. Which sample size consideration is unique to non-inferiority trials compared with superiority trials?
- Smaller samples are always required
- Need to pre-specify a non-inferiority margin
- Use of one-sided alpha is prohibited
- Power calculation ignores expected event rate
Correct Answer: Need to pre-specify a non-inferiority margin
Q8. The number needed to treat (NNT) is the reciprocal of which measure?
- Relative risk
- Absolute risk reduction
- Odds ratio
- Attributable fraction
Correct Answer: Absolute risk reduction
Q9. Which statistic measures agreement beyond chance for categorical diagnostic classifications between two raters?
- Pearson correlation coefficient
- Kappa statistic
- Intraclass correlation coefficient
- Spearman rank correlation
Correct Answer: Kappa statistic
Q10. In screening program evaluation, what does lead-time bias do to apparent survival time?
- It decreases observed survival time
- It has no effect on observed survival time
- It artificially increases observed survival time without changing time of death
- It improves disease prognosis biologically
Correct Answer: It artificially increases observed survival time without changing time of death
Q11. Diagnostic odds ratio (DOR) is defined as which of the following?
- (Sensitivity / (1 − Sensitivity)) / ((1 − Specificity) / Specificity)
- (True positives + True negatives) / Total tested
- (Positive predictive value) / (Negative predictive value)
Correct Answer: (Sensitivity / (1 − Sensitivity)) / ((1 − Specificity) / Specificity)
Q12. Which effect would verification bias (work-up bias) cause in diagnostic accuracy studies?
- Underestimation of specificity because only positives are verified
- Overestimation or underestimation of accuracy if verification depends on index test result
- No impact on accuracy estimates if reference standard is imperfect
- It only affects predictive values but not sensitivity or specificity
Correct Answer: Overestimation or underestimation of accuracy if verification depends on index test result
Q13. For a rare disease screening in a low-prevalence population, which value typically declines even if sensitivity and specificity remain constant?
- Sensitivity
- Specificity
- Positive predictive value
- Negative predictive value
Correct Answer: Positive predictive value
Q14. Which measure describes the average number of secondary infections produced by one infected individual in a fully susceptible population?
- Case fatality rate
- Basic reproduction number (R0)
- Attack rate
- Herd immunity threshold
Correct Answer: Basic reproduction number (R0)
Q15. In diagnostic accuracy studies, what is the Youden index used for?
- Estimating the prevalence of disease
- Identifying the optimal cut-off that maximizes sensitivity + specificity − 1
- Calculating predictive values directly from sensitivity and prevalence
- Adjusting for verification bias
Correct Answer: Identifying the optimal cut-off that maximizes sensitivity + specificity − 1
Q16. Which approach reduces selection bias in therapeutic trials by ensuring comparable groups at baseline?
- Blinding participants only
- Randomization with allocation concealment
- Using historical controls
- Allowing clinician choice of treatment
Correct Answer: Randomization with allocation concealment
Q17. During an outbreak investigation, which metric provides the proportion of exposed who develop disease within an incubation period?
- Prevalence
- Attack rate
- Incidence density
- Case fatality rate
Correct Answer: Attack rate
Q18. Which statistical measure accounts for both sensitivity and specificity and expresses how much a negative test reduces the odds of disease?
- Positive predictive value
- Negative predictive value
- Negative likelihood ratio
- Diagnostic yield
Correct Answer: Negative likelihood ratio
Q19. In trial monitoring, which analysis can inflate type I error if multiple interim looks are performed without adjustment?
- Final intent-to-treat analysis only
- Repeated significance testing at nominal alpha for each interim analysis
- Alpha spending with group sequential boundaries
- Pre-specifying stopping rules with adjustment
Correct Answer: Repeated significance testing at nominal alpha for each interim analysis
Q20. Herd immunity threshold can be approximated by which formula given R0?
- 1 − 1/R0
- 1/R0
- R0 − 1
- 1 − R0
Correct Answer: 1 − 1/R0
I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.
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