Bioassay: principles, scope, limitations and methods MCQs With Answer

Introduction: This blog presents a focused set of multiple-choice questions on bioassay principles, scope, limitations and methods tailored for M.Pharm students. It emphasizes the scientific basis of bioassays—dose–response relationships, potency and efficacy, graded versus quantal responses—and practical methodologies such as isolated tissue/organ bath studies, microbial assays, immunoassays and receptor-binding techniques. Statistical concepts required for accurate potency estimation, including parallel line, slope-ratio and logistic models, as well as validation parameters and ethical limitations, are also covered. These MCQs are designed to deepen conceptual understanding, reinforce experimental design and data interpretation skills, and prepare students for advanced coursework and research in pharmacological and toxicological screening methods.

Q1. What is the fundamental principle underlying a pharmacological bioassay?

• The assumption that all biological systems respond identically to a substance
• Reliance on the dose–response relationship between drug concentration and a measurable biological effect
• Using chemical analysis to quantify impurities in a sample
• Applying toxicokinetic models to predict metabolism

Correct Answer: Reliance on the dose–response relationship between drug concentration and a measurable biological effect

Q2. Which classification best describes bioassays based on the use of whole animals versus isolated tissues?

• Chemical and physical assays
• In vivo and in vitro bioassays
• Quantitative and qualitative assays
• Analytical and preparative assays

Correct Answer: In vivo and in vitro bioassays

Q3. How does a graded response differ from a quantal response in bioassay data?

• Graded responses are binary while quantal responses measure magnitude
• Graded responses measure magnitude of effect continuously, quantal responses record occurrence/non-occurrence in subjects
• Quantal responses require isolated organs but graded responses use whole animals
• There is no difference; both terms are interchangeable

Correct Answer: Graded responses measure magnitude of effect continuously, quantal responses record occurrence/non-occurrence in subjects

Q4. What is the primary assumption of the parallel line assay used for potency estimation?

• Dose–response curves are sigmoidal and have different maximal responses
• The test and standard produce linear dose–response relationships that are parallel within the chosen range
• The test substance is chemically identical to the standard
• Response variability is entirely due to measurement error

Correct Answer: The test and standard produce linear dose–response relationships that are parallel within the chosen range

Q5. When is the slope-ratio method preferred over the parallel line assay?

• When the dose–response curves are exactly parallel
• When dose–response curves have different slopes but proportional potency can still be computed
• When only a single dose can be tested
• When there is no measurable biological response

Correct Answer: When dose–response curves have different slopes but proportional potency can still be computed

Q6. Which mathematical model is commonly used to fit sigmoidal dose–response curves in immunoassays like ELISA?

• Linear regression without transformation
• Four-parameter logistic (4PL) model
• Kaplan–Meier survival model
• Gaussian mixture model

Correct Answer: Four-parameter logistic (4PL) model

Q7. What does ED50 represent in pharmacological bioassays?

• The maximum effect obtainable with a drug
• The dose producing 50% of the maximal effect in a graded response or effective in 50% of subjects for quantal assays depending on context
• The dose causing death in 50% of test animals
• The concentration required to occupy 50% of receptors in vitro only

Correct Answer: The dose producing 50% of the maximal effect in a graded response or effective in 50% of subjects for quantal assays depending on context

Q8. How is bioassay sensitivity best defined?

• The maximal effect achievable by a drug
• Ability of the assay to detect small differences in biological activity or low concentrations of analyte
• The rate at which the assay can process samples
• The specificity of the assay for a single analyte

Correct Answer: Ability of the assay to detect small differences in biological activity or low concentrations of analyte

Q9. What is the main difference between potency and efficacy in bioassay interpretation?

• Potency describes maximal response; efficacy describes dose required
• Potency refers to the amount of drug required to produce a given effect; efficacy refers to the maximal effect a drug can produce
• They are synonymous terms in pharmacology
• Efficacy applies only to toxicology, potency only to pharmacology

Correct Answer: Potency refers to the amount of drug required to produce a given effect; efficacy refers to the maximal effect a drug can produce

Q10. Which statistical methods are most appropriate for analyzing quantal bioassay data?

• Linear regression on raw response magnitudes
• Probit or logit analysis for dose–response proportions
• Fourier transform analysis
• Principal component analysis

Correct Answer: Probit or logit analysis for dose–response proportions

Q11. Which classical methods are used to estimate median lethal dose (LD50) from quantal mortality data?

• ANOVA and Tukey test
• Reed–Muench and Behrens–Kärber methods
• Parallel line assay only
• Curve fitting using Hill equation exclusively

Correct Answer: Reed–Muench and Behrens–Kärber methods

Q12. Which of the following is NOT a major source of variability in bioassay results?

• Biological variation among test organisms
• Environmental factors like temperature and pH
• Operator technique and instrument calibration
• Chemical purity of the buffer alone if everything else is controlled perfectly

Correct Answer: Chemical purity of the buffer alone if everything else is controlled perfectly

Q13. Which set of validation parameters is essential for a reliable bioassay?

• Accuracy, precision, linearity, specificity and sensitivity
• Only sample throughput and cost
• Color and odor of reagents
• Number of investigators on the team

Correct Answer: Accuracy, precision, linearity, specificity and sensitivity

Q14. What does an organ bath isolated tissue assay typically measure?

• Chemical composition of a drug
• Contractile or relaxant responses of isolated smooth or striated muscle to pharmacological agents
• Genetic mutations in cultured cells
• Plasma protein binding in humans

Correct Answer: Contractile or relaxant responses of isolated smooth or striated muscle to pharmacological agents

Q15. Microbial bioassays are classically used for which purpose in pharmacology?

• Measuring blood-brain barrier penetration
• Estimating potency of antibiotics and some hormones by growth inhibition or stimulation of microorganisms
• Assessing receptor internalization kinetics
• Determining hepatic metabolism rates

Correct Answer: Estimating potency of antibiotics and some hormones by growth inhibition or stimulation of microorganisms

Q16. Which limitation most directly affects extrapolation of animal bioassay results to humans?

• High throughput capacity of animal assays
• Interspecies differences in pharmacokinetics and receptor distribution
• Ease of dose administration in animals
• Identical metabolism between species

Correct Answer: Interspecies differences in pharmacokinetics and receptor distribution

Q17. Why is the inclusion of a reference standard essential in quantitative bioassays?

• Standards increase the toxicity of the sample
• To enable relative potency estimation and construct a reliable calibration/dose–response relationship
• Standards are only used for instrument calibration, not biological assays
• They are required to reduce assay time

Correct Answer: To enable relative potency estimation and construct a reliable calibration/dose–response relationship

Q18. Which statistical test is appropriate for comparing means across more than two dose groups in a graded bioassay?

• Student’s paired t-test only
• One-way ANOVA followed by appropriate post-hoc comparisons
• Fisher’s exact test applied to each pair
• Chi-square test on continuous outcomes

Correct Answer: One-way ANOVA followed by appropriate post-hoc comparisons

Q19. In a parallel line assay, what does a non-significant test for non-parallelism indicate?

• The dose–response curves are significantly different in slope
• There is no evidence against the assumption of parallelism; curves can be treated as parallel
• The assay is invalid and must be discarded
• The maximal responses differ and potency cannot be estimated

Correct Answer: There is no evidence against the assumption of parallelism; curves can be treated as parallel

Q20. Which modern alternatives help reduce animal use in bioassays while retaining relevance to human biology?

• In vitro cell-based assays, receptor binding studies and in silico modeling
• Increasing animal numbers to improve statistical power
• Using longer observation periods in animal tests
• Relying solely on historical animal data without new testing

Correct Answer: In vitro cell-based assays, receptor binding studies and in silico modeling

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