Assay Types and Techniques

Podcast Beta

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the main purpose of testing infected patients' sputum in relation to antibiotics?

To measure the concentration of the antibiotic in the body

To analyze the overall health condition of the patient

To determine the presence of viral infections

To identify the specific antibiotic for effective treatment (correct)

What disadvantage is associated with biological assays mentioned in the content?

They require minimal expertise to execute

They can only detect non-active substances

They can introduce variability in response (correct)

They always yield exact numeric results

Which of the following is a disadvantage of using bioassays?

They typically require less animal testing

They can be time-consuming and costly (correct)

They are considered fast and inexpensive

They measure only large quantities of active substances

What can be inferred about compounds with different chemical compositions but similar biological activity?

They may require complex analysis methodologies for evaluation Signup and view all the answers

What does tachyphylaxis refer to in the context of drug response?

A decrease in the response following initial administration Signup and view all the answers

What is a defining characteristic of a quantal bioassay?

It involves an all or none response in individuals. Signup and view all the answers

Which method of comparison is preferred for testing the therapeutic properties of a drug?

Comparison with a standard substance. Signup and view all the answers

What level of accuracy is considered excellent in bioassays?

Within 10% of true value. Signup and view all the answers

Which factor does NOT influence biological testing procedure?

Testing duration. Signup and view all the answers

What is one of the key purposes of conducting a bioassay?

To measure the response of living animals to chemical contaminants. Signup and view all the answers

Which bioassay example demonstrates the comparison of LD50 values?

Digitalis inducing cardiac arrest. Signup and view all the answers

Which animal is NOT commonly used in the quantitative biological tests?

Cat. Signup and view all the answers

Graded bioassay is characterized by which of the following?

A response that varies with the dose administered. Signup and view all the answers

What is specifically meant by a 'standard preparation'?

A selective representative sample for measurement Signup and view all the answers

Which type of preparation uses highly recognized and authorized standards?

International standard preparation Signup and view all the answers

What is the main purpose of bioassays?

To determine concentration and biological activity Signup and view all the answers

Which statement about potency is true?

Potency indicates the amount needed to produce a given effect Signup and view all the answers

What distinguishes qualitative bioassays from quantitative bioassays?

Qualitative bioassays measure physical effects that cannot be quantified. Signup and view all the answers

Which pair of drugs represents low potency based on their effects?

Ibuprofen and acetylsalicylic acid Signup and view all the answers

When a country develops its own standards for preparations, what must it adhere to?

Its own local laws and regulations Signup and view all the answers

In biological assays, the term 'potency' refers to which of the following?

The amount required to produce a specified effect Signup and view all the answers

What is the primary purpose of an assay in laboratory medicine?

To qualitatively or quantitatively measure the presence or activity of a target entity Signup and view all the answers

Which type of assay employs the binding between an antigen and an antibody?

Immunoassay Signup and view all the answers

What is a significant drawback of bioassays compared to chemical assays?

Higher costs involved Signup and view all the answers

In which situation would a bioassay be preferred over a chemical assay?

When chemical methods are too complex or unavailable Signup and view all the answers

Which of the following statements is true regarding bioassays?

Bioassays primarily focus on the activity of interest. Signup and view all the answers

How do bioassays and chemical assays compare in terms of precision?

Chemical assays are more precise than bioassays. Signup and view all the answers

Why might a bioassay be necessary if the active principle of a drug is not known?

Bioassays can measure drug efficacy without needing to isolate the active principle. Signup and view all the answers

Which characteristic distinguishes chemical assays from bioassays?

Chemical assays can be performed more quickly. Signup and view all the answers

Study Notes

Assay

An investigative procedure used in various fields like laboratory medicine, pharmacology, and molecular biology to qualitatively or quantitatively measure the presence or amount of a target entity (analyte), which can be a drug, biochemical substance, or organic sample.

Types of Assay

Chemical Assay: Involves the separation, identification, and quantification of chemical components in materials.
Immunoassay: A technique that utilizes the binding between an antigen and its antibody to identify and quantify specific antigens or antibodies in a sample.
Bioassay: A biological testing procedure for estimating the concentration of a pharmaceutical drug substance in a formulated drug product or bulk material.

Biological Assay

Involves administering a specific potency of a drug to animals or human volunteers to compare drug responses with established standards.

Comparison of Chemical & Bioassay

Bioassay:
- Less precise
- More time consuming
- More expensive
- Active constituent & structure not known
- More sensitive
- More manpower required
- Difficult to handle
Chemical Assay:
- More precise
- Less time consuming
- Less expensive
- Active constituent & structure fully established
- Less sensitive
- Less manpower required
- Easy to handle

Indications of Bioassay

When a chemical method is not available, too complex, or insensitive to low doses (e.g., histamine).
When the active principle of a drug is unknown (e.g., insulin).
When the chemical composition of a drug is unknown but has the same pharmacological action (e.g., cardiac glycosides).
When the active principle cannot be isolated (e.g., posterior pituitary extract, insulin).
When the biological activity of a drug cannot be defined by a chemical assay (e.g., cis and trans forms of methylphenidate).
When it's not possible to separate interfering substances (e.g., Vitamin D).

Principles of Bioassay

All bioassays should be compared against a standard drug.
The standard and new drug should be as identical as possible.
The assayed activity should be the activity of interest.
The pharmacological response produced should be reproducible under identical conditions.
The method of comparison should preferably (but not essentially) test the therapeutic property of the drug.
Individual variations must be minimized.

Classification of Bioassay

Quantal: All or none response in all individuals (e.g., digitalis-induced cardiac arrest in guinea pigs, hypoglycemic convulsions in mice by insulin, LD50 calculation in mice or rats).
Graded: Effect is produced gradually depending on the dose (e.g., contraction of smooth muscle preparation).

Accuracy Limits of Bioassay

Accuracy within 20% of the true value is considered good.
Accuracy within 10% of the true value is considered excellent.

Biological Testing Procedure Dependency

Biological assay depends on the size of the dose and the potency of the drug.
While the effect produced in animals may not always be the same as in humans, there are exceptions.

Partial List of Official Quantitative Biological Tests

Drug and Dosage Form: Antibiotics, Insulin, Digitalis & other glycosides, Vitamin A & D, Parathyroid drugs, Posterior pituitary, Tubocurarine Chloride
Test Animal(s): Suitable microorganism, Rabbit & Mice, Pigeon & Guinea Pig, Rat, Dog, Rat, Rabbit

Purpose of Bioassay

Determine the quantity of a test sample required to produce an equivalent biological response to a standard substance.
Measure the pharmacological activity of new or chemically undefined substances.
Test method employed in measuring the response of living animals to the toxicity of chemical contaminants.
Investigate the function of endogenous mediators.
Determine the concentration and potency of an unknown substance.
Improve and maintain standards of basic environmental conditions affecting human well-being (e.g., pollutants released by particular sources).
Determine the specificity of compounds to be used (e.g., penicillin's are effective against G+ve but not G-ve).

Preparation of Standard

A selective representative sample of a substance used as a basis for measurement.
Should be uniform quality and stable.

Types of Standard Preparation

International standard and reference standard: Highly recognized and authorized standard (e.g., USP units).
British standard and reference standard: Country-specific standards used according to its own laws.

Potency

Measurement of drug activity expressed in terms of the amount required to produce an effect of a given intensity.

Advantages of Bioassay

Determine the concentration, purity, or biological activity of a substance.
Compare the effect of a substance on an organism, tissue cells, enzymes, or receptors to a standard preparation.
Can be qualitative or quantitative.
Estimate the concentration or potency of a substance by measuring its biological response.
Standardize drugs, vaccines, toxins, poisons, disinfectants, and antiseptics.
Determine the specificity of a compound (e.g., penicillin's are effective against G+ve but not G-ve).
Assay complex substances that cannot be effectively analyzed by simple techniques.
Assay samples with different chemical compositions but the same biological activity.
Assay samples where no other methods are available.
Assay biological products like toxins, antitoxins, and sera.
Measure minute quantities of active substances (nano mole & pico mole).
Detect active substances without prior extraction or treatment.

Disadvantages of Bioassay

Variability in response.
Large number of animals required.
Expertise required in experimental design, execution, and data analysis, making it expensive and time consuming.
Time-related changes in the sensitivity of the test organ.
Tachyphylactic responses (decreased response to a drug after initial administration).

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Explore the various types of assays used in laboratory medicine, pharmacology, and molecular biology. This quiz covers chemical assays, immunoassays, and bioassays, detailing their methods and applications. Test your knowledge on how these techniques measure specific substances and analyze their effectiveness.