Introduction: Bioassays are core experimental methods in pharmaceutical science that quantify a drug’s biological activity, potency and efficacy using biological systems. For B. Pharm students, mastering in vivo and in vitro bioassays, dose–response relationships, ED50/LD50 concepts, parallel line and slope‑ratio methods, and assay validation parameters (precision, accuracy, linearity, specificity) is vital for drug standardization, vaccine and hormone potency testing, and regulatory compliance. Applications include insulin and antibiotic potency, vaccine batch release, antitoxin/antivenom evaluation, and pharmacodynamic profiling. Emphasis on statistical analysis, biological reference standards, and ethical 3R principles (replacement, reduction, refinement) ensures reliable, reproducible results. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. Which of the following best defines a bioassay?
- An analytical method using chemical reagents to measure purity
- A biological procedure to determine the potency or concentration of a substance by its effect on living systems
- A microbiological culture test to detect contaminants only
- A physicochemical test to measure melting point of a drug
Correct Answer: A biological procedure to determine the potency or concentration of a substance by its effect on living systems
Q2. What is the primary difference between graded and quantal bioassays?
- Graded assays measure binary outcomes; quantal assays measure continuous responses
- Graded assays assess individual continuous responses; quantal assays measure all-or-none responses in a population
- Graded assays are always in vitro; quantal assays are always in vivo
- Graded assays use chemical standards only; quantal assays use biological standards only
Correct Answer: Graded assays assess individual continuous responses; quantal assays measure all-or-none responses in a population
Q3. ED50 in a bioassay refers to:
- The dose required to kill 50% of test animals
- The effective dose that produces 50% of the maximal response
- The maximal effect observed at infinite dose
- The dose that produces no effect in 50% of subjects
Correct Answer: The effective dose that produces 50% of the maximal response
Q4. Which statistical method is commonly used to analyze quantal bioassay data (e.g., LD50)?
- Regression tree analysis
- Probit or logit analysis
- Kaplan–Meier survival analysis
- Principal component analysis
Correct Answer: Probit or logit analysis
Q5. In a parallel line bioassay, what assumption is essential for valid potency estimation?
- The slopes of dose–response lines for test and standard are equal
- The intercepts of test and standard are identical
- The responses are binary only
- The sample sizes must be equal in each group
Correct Answer: The slopes of dose–response lines for test and standard are equal
Q6. Slope‑ratio assay is most appropriate when:
- The dose–response relationship is parallel between test and standard
- The dose–response relationship passes through the origin and slope differs between preparations
- Only single-dose comparison is available
- The response is quantal and not graded
Correct Answer: The dose–response relationship passes through the origin and slope differs between preparations
Q7. Which parameter of validation assesses closeness between measured value and true value in a bioassay?
- Precision
- Specificity
- Accuracy
- Robustness
Correct Answer: Accuracy
Q8. Biological standard (reference standard) in bioassays is used to:
- Control pH of assay medium
- Calibrate and compare potency of test samples
- Increase biosafety level of the assay
- Sterilize reagents before use
Correct Answer: Calibrate and compare potency of test samples
Q9. Which of the following is an application of bioassay in vaccine quality control?
- Determination of vaccine sedimentation rate
- Potency estimation by neutralization or protection assays
- Measurement of vaccine color
- Assessing solubility in organic solvents
Correct Answer: Potency estimation by neutralization or protection assays
Q10. In cell‑based reporter gene bioassays, the reporter is used to:
- Physically separate cells from medium
- Provide a measurable signal proportional to biological activity
- Kill non‑responding cells selectively
- Stabilize the drug molecule
Correct Answer: Provide a measurable signal proportional to biological activity
Q11. Which factor is most critical to control to reduce biological variability in in vivo bioassays?
- Ambient light intensity only
- Animal strain, age, sex and housing conditions
- Battery level of instruments
- Color of the dosing syringe
Correct Answer: Animal strain, age, sex and housing conditions
Q12. The unit “IU” (International Unit) is used in bioassays to:
- Express chemical purity in percentage
- Quantify biological activity based on an agreed reference
- Measure molecular weight
- Indicate sterility level
Correct Answer: Quantify biological activity based on an agreed reference
Q13. Which is a major advantage of in vitro bioassays over in vivo tests?
- They always give more clinically relevant results
- Lower cost, higher throughput and fewer ethical concerns
- No requirement for statistical analysis
- They never require reference standards
Correct Answer: Lower cost, higher throughput and fewer ethical concerns
Q14. Which outcome describes ‘potency’ in the context of bioassays?
- The maximum effect a drug can produce regardless of dose
- The dose required to produce a defined response relative to a standard
- The time taken to reach peak plasma concentration
- The number of metabolites formed
Correct Answer: The dose required to produce a defined response relative to a standard
Q15. The therapeutic index (TI) relates to bioassay data by comparing:
- Drug solubility vs permeability
- Pharmacokinetic half‑life vs bioavailability
- Toxic dose (e.g., LD50) to effective dose (e.g., ED50)
- The pH‑stability range to storage temperature
Correct Answer: Toxic dose (e.g., LD50) to effective dose (e.g., ED50)
Q16. In a neutralization bioassay for antivenom, the primary endpoint is:
- Color change of the medium
- Prevention of venom‑induced toxicity or death in the test model
- Increase in pH of the reaction mixture
- Formation of crystalline precipitate
Correct Answer: Prevention of venom‑induced toxicity or death in the test model
Q17. Which statistical parameter indicates precision in repeated bioassay measurements?
- Mean recovery percentage
- Standard deviation or coefficient of variation (CV)
- Limit of detection
- Nominal concentration
Correct Answer: Standard deviation or coefficient of variation (CV)
Q18. During validation, specificity of a bioassay means:
- The assay can detect the analyte over a wide concentration range
- The assay responds only to the intended biological activity without interference
- The assay can be performed by any technician without training
- The assay is robust to extreme temperature changes
Correct Answer: The assay responds only to the intended biological activity without interference
Q19. Which is a common challenge when using biological reference standards?
- They are chemically inert and do not react
- Limited availability, batch variability and stability over time
- They eliminate the need for controls
- They do not require storage conditions
Correct Answer: Limited availability, batch variability and stability over time
Q20. What is the role of a placebo control in certain bioassays?
- To provide maximal biological activity
- To account for non‑specific or background responses
- To enhance potency of the test sample
- To sterilize the test system
Correct Answer: To account for non‑specific or background responses
Q21. Which assay design reduces animal use by allowing multiple dose groups to be compared with a single standard curve?
- Fixed‑dose single point assay
- Parallel line assay with pooled controls
- Slope‑ratio assay with serial dilutions
- Design using multiple independent standard curves for each dose
Correct Answer: Slope‑ratio assay with serial dilutions
Q22. A dose–response curve with a steep slope indicates:
- Large change in response over a small dose range (high sensitivity)
- No change in response with dose
- The assay is invalid
- Wide dynamic range with low sensitivity
Correct Answer: Large change in response over a small dose range (high sensitivity)
Q23. Which parameter determines the lowest concentration that produces a reliably measurable biological response?
- Linearity
- Limit of detection (LOD)
- Specificity
- Stability
Correct Answer: Limit of detection (LOD)
Q24. In vaccine potency bioassays, serological assays often measure:
- Antibody titers that correlate with protective immunity
- Protein melting point
- Rate of diffusion in agar
- Concentration of preservatives only
Correct Answer: Antibody titers that correlate with protective immunity
Q25. Which practice improves reproducibility of bioassays across laboratories?
- Using different reference materials in each lab
- Standardized protocols, common reference standards and inter‑laboratory calibration
- Avoiding documentation of conditions
- Changing assay endpoints frequently
Correct Answer: Standardized protocols, common reference standards and inter‑laboratory calibration
Q26. When an antagonist is tested in a bioassay against an agonist, the observed rightward shift in the agonist dose–response curve without change in maximum response indicates:
- Non‑competitive antagonism
- Surmountable competitive antagonism
- Agonist degradation
- Irreversible receptor activation
Correct Answer: Surmountable competitive antagonism
Q27. Robustness of a bioassay refers to:
- Ability to remain unaffected by small deliberate variations in method parameters
- Highest possible sensitivity only
- Speed at which results are generated
- Cost of reagents used
Correct Answer: Ability to remain unaffected by small deliberate variations in method parameters
Q28. Which bioassay type is most suitable for measuring insulin potency?
- Agar diffusion antibiotic assay
- Glucose uptake or hypoglycemic response in animal or cell models
- pH titration assay
- Gas chromatography analysis
Correct Answer: Glucose uptake or hypoglycemic response in animal or cell models
Q29. Why is randomization important in designing bioassays?
- To increase experimental bias
- To ensure allocation of treatments is not influenced by systematic factors and reduce confounding
- To eliminate the need for controls
- To ensure identical responses among all subjects
Correct Answer: To ensure allocation of treatments is not influenced by systematic factors and reduce confounding
Q30. The 3R principles in bioassay ethics stand for:
- Reduce, Reuse, Recycle
- Replacement, Reduction, Refinement of animal use
- Randomize, Replicate, Record
- Recover, Resuscitate, Rehabilitate
Correct Answer: Replacement, Reduction, Refinement of animal use
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.
Mail- Sachin@pharmacyfreak.com