Bioassay principles are essential in B.Pharm for assessing biological potency, dose–response relationships, and pharmacological activity of drugs. This introduction covers core bioassay concepts—types (in vivo, in vitro), graded versus quantal responses, dose–response curves, potency versus efficacy, ED50/EC50, assay sensitivity and specificity, standardization, calibration curves, parallel line and slope‑ratio methods, and relevant statistical analyses such as probit and log‑dose transformations. Emphasis on assay validation, controls, units like IU, factors affecting variability, and Good Laboratory Practice readies students for designing reliable bioassays, interpreting results, and supporting formulation evaluation and regulatory submissions. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. What is the primary purpose of a bioassay in pharmaceutical analysis?
- To measure chemical purity of a compound
- To determine biological potency or activity of a substance
- To calculate manufacturing cost
- To test dissolution in simulated fluids
Correct Answer: To determine biological potency or activity of a substance
Q2. Which of the following best distinguishes potency from efficacy?
- Potency is the maximum effect; efficacy is the dose required
- Potency is the dose producing a given effect; efficacy is the maximum achievable effect
- Potency and efficacy are identical terms
- Potency refers to toxicity; efficacy refers to safety
Correct Answer: Potency is the dose producing a given effect; efficacy is the maximum achievable effect
Q3. ED50 in a graded dose–response bioassay refers to:
- The dose lethal to 50% of subjects
- The dose producing 50% of the maximum response
- The dose at which 50% of the drug is metabolized
- The dose producing effect in 50% of the population
Correct Answer: The dose producing 50% of the maximum response
Q4. A quantal bioassay measures:
- Continuous magnitude of response in individual subjects
- Binary outcomes such as alive/dead or response/no response across a group
- Chemical concentration by spectrophotometry
- Receptor binding kinetics in vitro
Correct Answer: Binary outcomes such as alive/dead or response/no response across a group
Q5. Which method is commonly used for potency comparison when dose–response curves are parallel?
- Slope‑ratio method
- Parallel line assay
- Nonlinear mixed effects modelling
- ANOVA without transformation
Correct Answer: Parallel line assay
Q6. The slope‑ratio method is preferred when:
- Responses reach a clear common maximum and curves are parallel
- Curves are linear and pass through origin with proportional responses
- Only qualitative results are obtained
- There is no standard available
Correct Answer: Curves are linear and pass through origin with proportional responses
Q7. Assay sensitivity refers to:
- The ability to detect small differences in potency or low concentrations
- The degree to which an assay gives the same result repeatedly
- The maximum response achievable in the assay
- The specificity of the assay to one compound
Correct Answer: The ability to detect small differences in potency or low concentrations
Q8. Which statistical transformation is commonly applied to quantal dose–response data for analysis?
- Square root transformation
- Probit transformation
- Reciprocal transformation
- Fisher’s exact transformation
Correct Answer: Probit transformation
Q9. In bioassay validation, intra‑assay variability refers to:
- Variability between different laboratories
- Variability within the same assay run
- Variability between manufacturers
- Variability over months or years
Correct Answer: Variability within the same assay run
Q10. International Units (IU) are used in bioassays to express:
- Chemical molarity only
- Biological activity relative to an international standard
- The cost per international shipment
- The stability index of a drug
Correct Answer: Biological activity relative to an international standard
Q11. A calibration curve in a bioassay is primarily used to:
- Measure impurity profiles
- Relate known concentrations or potencies of standard to measured response
- Assess patient compliance
- Determine dissolution rate only
Correct Answer: Relate known concentrations or potencies of standard to measured response
Q12. Which factor is most critical to minimize biological variability in animal bioassays?
- Using different animal strains randomly
- Standardizing animal strain, age, sex, and housing conditions
- Feeding animals at random times
- Changing room temperature frequently
Correct Answer: Standardizing animal strain, age, sex, and housing conditions
Q13. Graded responses differ from quantal responses in that graded responses:
- Are binary outcomes across a population
- Measure magnitude of response in each individual across doses
- Are used only in in vitro tests
- Do not allow ED50 determination
Correct Answer: Measure magnitude of response in each individual across doses
Q14. Which assumption is essential for valid parallel line assays?
- Dose–response curves must be nonparallel
- Responses are independent of dose
- Test and standard preparations produce parallel dose–response curves within a certain range
- Maximum responses must be zero
Correct Answer: Test and standard preparations produce parallel dose–response curves within a certain range
Q15. Probit analysis converts percentage responses into a scale that is approximately:
- Logarithmic
- Normally distributed
- Exponential
- Uniform
Correct Answer: Normally distributed
Q16. EC50 denotes:
- The effective concentration producing 50% of maximal effect in vitro
- The lethal concentration for 50% of organisms
- The economic cost at 50% production
- The elimination constant at steady state
Correct Answer: The effective concentration producing 50% of maximal effect in vitro
Q17. Which parameter indicates assay precision across repeated measurements?
- Limit of detection (LOD)
- Coefficient of variation (CV)
- Maximum response (Emax)
- Potency ratio
Correct Answer: Coefficient of variation (CV)
Q18. When performing a bioassay, a positive control is used to:
- Establish absence of response
- Confirm assay is capable of detecting a known effect
- Measure contamination only
- Serve as solvent blank
Correct Answer: Confirm assay is capable of detecting a known effect
Q19. Which analysis is appropriate to compare potencies of two preparations with parallel log‑dose responses?
- Student’s t‑test on raw responses
- Parallel line assay with relative potency estimation
- Kaplan–Meier survival analysis
- Chi‑square test for independence
Correct Answer: Parallel line assay with relative potency estimation
Q20. Limit of quantification (LOQ) in bioassays is defined as:
- The lowest concentration that can be detected but not quantified
- The lowest concentration that can be quantified with acceptable accuracy and precision
- The maximum concentration allowable by regulations
- The point of zero response
Correct Answer: The lowest concentration that can be quantified with acceptable accuracy and precision
Q21. Which is a common cause of bias in biological assays?
- Random sampling
- Poor standardization of reference material
- High sample throughput
- Using log transformations
Correct Answer: Poor standardization of reference material
Q22. In a bioassay context, ‘specificity’ refers to:
- Ability of assay to detect only the analyte of interest without interference
- Degree of repeatability within a run
- How sensitive the assay is to low concentrations
- How quickly results are obtained
Correct Answer: Ability of assay to detect only the analyte of interest without interference
Q23. Which plot linearizes a sigmoid dose–response curve for easier ED50 estimation?
- Linear plot of dose versus response
- Log(dose) versus response
- Reciprocal dose plot
- Square of dose plot
Correct Answer: Log(dose) versus response
Q24. In slope‑ratio assays, the ratio of slopes between test and standard gives:
- Absolute toxicity
- Relative potency when intercepts are common or constrained
- Assay sensitivity index only
- Maximum efficacy difference
Correct Answer: Relative potency when intercepts are common or constrained
Q25. Good Laboratory Practice (GLP) in bioassays requires documentation of:
- Only final results
- All procedures, raw data, SOPs, and deviations
- Staff salaries
- Marketing strategies
Correct Answer: All procedures, raw data, SOPs, and deviations
Q26. Which factor can cause nonparallelism between test and standard dose–response curves?
- Equal potencies
- Different mechanisms of action or impurities affecting response slope
- Perfect standardization of assay conditions
- Identical sample matrices
Correct Answer: Different mechanisms of action or impurities affecting response slope
Q27. Bioassay ‘accuracy’ refers to:
- Closeness of measured values to the true or accepted reference value
- Repeatability across replicates only
- Sensitivity at lower limits only
- Speed of assaying samples
Correct Answer: Closeness of measured values to the true or accepted reference value
Q28. Which is an advantage of in vitro bioassays over in vivo assays?
- They always predict clinical efficacy better
- Lower ethical concerns, higher throughput, and reduced variability
- They eliminate need for statistical analysis
- They never require calibration with standards
Correct Answer: Lower ethical concerns, higher throughput, and reduced variability
Q29. Inter‑assay variability is best reduced by:
- Changing assay protocol each run
- Using a well‑characterized reference standard and consistent procedures across runs
- Using different analyst techniques each time
- Varying incubation times randomly
Correct Answer: Using a well‑characterized reference standard and consistent procedures across runs
Q30. Which outcome indicates an assay is fit for purpose in regulatory bioassay validation?
- Uncontrolled variability and unknown accuracy
- Demonstrated accuracy, precision, specificity, and suitable limits of detection/quantification
- No documentation of controls or standards
- Only qualitative descriptions without numerical criteria
Correct Answer: Demonstrated accuracy, precision, specificity, and suitable limits of detection/quantification
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