Delving into the realm of scientific research, the 3 main types of assays available offers an insightful overview of the diverse methodologies used in laboratories. This guide focuses on elucidating the types of assays, each distinct in their application and significance. Whether for diagnostic purposes, research, or pharmaceutical development, understanding these assays is pivotal for professionals and students alike. This piece serves as a navigational tool, shedding light on the intricacies and applications of each assay type in modern science.
Exploring Laboratory Investigations: The 3 Main Types of Assays Available
Detection systems use various forms of signal amplification—for instance, ligand-binding assays, immunoassays, and electrochemiluminescence—to convert an analyte into a detectable signal, including turbidimetry, colour detection systems like urine dipstick assays, and light or electrical detection (ELISA) to measure an analyte’s levels in solution.
Assays involve both pre- and post-analytic steps that need to be managed effectively, including communication and specimen handling steps that are typically part of an assay procedure.
This table provides an overview of various types of assays used in different fields, such as laboratory medicine, environmental biology, and pharmacology. It discusses bioassays, quantitative and qualitative assays, as well as their specific applications and methodologies.
| The type of assay | Description |
| Bioassay | It employs living organisms to detect chemicals and assess their toxic effects. Environmental health science and toxicology are used to screen contaminants. |
| Quantitative Assay | Measures the presence or amount of an analyte, such as elements, compounds, cells, or enzymes. It requires extensive preanalytical processing and is frequently automated for high throughput. |
| Qualitative Assay | Analyses the presence of substances qualitatively or semi-quantitatively, often more sensitive than chemical analyses but less precise. Utilises techniques like ELISA, RIA, electrophoresis, and chromatography. |
| Detection Systems | Various systems, like ligand-binding assays, immunoassays, and electrochemiluminescence, convert analytes into detectable signals (e.g., turbidimetry, colour detection). |
| Pre- and post-analysis steps | It includes specimen handling and communication, which are critical for assay accuracy. |
| Environmental Monitoring | Monitoring contaminants in soil, water, and food is the main purpose of bioassays. Indicates the presence of harmful toxins. |
| Pharmaceutical Standardisation | Bioassays are used to compare substances with known potencies to assess the quality of pharmaceuticals and vaccines. |
| Protein Quantification | Techniques like Bradford, Folin-Lowry, BCA, and Quantitative Dot Blot (QDB) for measuring protein levels. |
| Serologic Assays | Antibody concentrations are used to diagnose infections and monitor immune responses. |
| Research Applications | Qualitative research is used to study social interactions and processes as well as generate hypotheses for quantitative testing. |
A Scientific Journey: Exploring the Diversity of Assays: A Scientific Journey
“Types of Assays” delves into the fascinating world of assay methods, a critical component in scientific research, medical diagnostics, and environmental analysis. This blog aims to unravel the complexities and variations among different assay types, offering readers a detailed view of their applications and methodologies. From the precision of quantitative assays in measuring specific analytes to the sensitivity of qualitative assays in detecting subtle changes, each type of assay plays a unique role in advancing our understanding of biological and chemical phenomena. Whether you’re a seasoned researcher, a student in the sciences, or simply curious about the tools that shape modern scientific inquiry, this blog provides a clear and engaging exploration of the various types of assays and their impact on multiple disciplines. Join us as we navigate through the intricacies of these essential scientific techniques.
Bioassay
Bioassay is an experimental technique that uses living organisms to detect chemicals and assess their toxic effects. It falls under the realms of toxicology (which investigates chemicals’ impact on living things) and environmental health science. Bioassays are often employed in screening soil, water, and food samples for potential contaminants; additionally, they serve as valuable tools in identifying toxicants that are detrimental to humans, wildlife, or contaminated matrices that must be identified quickly for monitoring purposes.
Bioassays frequently employ indicator species (e.g., Crassostrea gigas, the Pacific oyster) that are sensitive to particular chemicals or parameters, so it is critical that each sample analysed in bioassay is entered correctly into EIM with its correct taxonomic name and code; see the Bioassay Result Entry Template for guidance in entering this information correctly.
Bioassays come in all forms, from qualitative tests to more intricate cell-based assays. Most tests take place in laboratories using special tissue culture equipment like laminar flow hoods to ensure cells remain sterile during culture, while certain assays (such as those that evaluate cytokine concentrations in cell cultures) require using CO2 incubators in order to provide ideal temperatures and avoid mycoplasma contamination.
Bioassays are one of the most frequently employed toxicity testing techniques, used to ascertain if chemicals or materials are toxic to living organisms by measuring their ability to disrupt cell structure or impair normal functions. Bioassay results can also be used to identify potentially hazardous chemicals present in soil, potable water and wastewater supplies, food products, or other materials, as well as assess acute and chronic toxicity risks from mixtures contaminated with multiple contaminants.
Pharmacodynamic or biological standardisation tests are another type of bioassay that compares a substance with internationally accepted reference materials with known potencies, making them an especially useful way of assessing pharmaceuticals and vaccines for quality assessment purposes.
When submitting bioassay data to EIM, it is imperative that laboratory replicates are included for all tests. At minimum, 5 replicates should be included for marine sediment bioassays and 8 for freshwater bioassays. Laboratory replicates are separate samples that are analysed at different times using the same methods and processes. Bioassay must identify its laboratory replicates in its Bioassay Lab Replicate ID field (column AC). If replication issues were encountered, these should be described in the Bioassay Data Acceptability Field (column AK). For all bioassays conducted, it is also highly recommended to provide raw measurement data tables. These will usually contain fields such as ash-free dry weight, initial biomass counts, and stock density counts; such tables provide important comparison opportunities between laboratory data and site investigations.
Quantitative
A quantitative assay is a type of test used in lab medicine, mining, metallurgy, pharmacology, and environmental analysis to qualitatively or quantitatively assess the presence or amount of an analyte (also called an analyte), such as elements, compounds, cells, proteins, or enzymes found within organic samples or organisms. An analyte’s intensive properties, such as colour absorbance, emission, redox activity, fluorescence intensity, or fluorescence intensity, are measured and compared to an appropriate standard (either a calibration curve or pass/fail standard intensity) before producing results in milligrammes, micrograms, or nanograms.
Quantitative assays tend to be more complicated than their qualitative or semi-quantitative counterparts, typically requiring extensive preanalytical processing of samples in order to expose target analytes in an identifiable and quantifiable form for detection and discrimination. This may include centrifugation, washing, or filtration, as well as epitope retrieval in immunoassays or fragmentation by mass spectrometry.
Many of these techniques are automated, so they can be performed with speed, accuracy, and consistency at high throughput. However, they are sensitive to fluctuating sample conditions and must be carefully managed for accurate measurements, which is why such methods are typically conducted by specialised laboratories for diagnostic or research use rather than commercial or professional clinical applications.
UNC Chemistry MS Core offers an array of quantitative assays that can be customised to the investigator’s needs. Prior to developing any method, it is critical that collaboration on analyte physicochemical properties take place between collaborators, as well as consultation with UNC Chemistry MS Core employees on identifying an ideal methodology. When making solutions of known concentrations for use in assays, it is recommended that authenticated analytical reference standards with known identities and purity levels be used, as authenticated analytical reference standards provide solutions of known identities and purity for use during assays.
Utilising a standard calibrator at each experimental run helps ensure the reproducibility of an assay, particularly for quantitative measurements that require the calculation of accurate values for their target analyte. Popular techniques for protein quantification are Bradford, Folin-Lowry, and Bicinchoninic Acid (BCA) assays, while recently, quantitative dot blot (QDB) has also been introduced as a method to decrease the time taken to quantify proteins.
Quantitative serologic assays are relatively rare, but they are increasingly being developed for a variety of infectious disease pathogens. These assays measure antibody concentrations and allow longitudinal monitoring of adaptive or humoral immune responses related to previous infections, making them invaluable when diagnosing new infections or monitoring therapeutic antiviral agents or vaccines.
Qualitative
However, they will have the chance to get in contact with one another and form friendships that will last well beyond their lifetime. An assay is a type of analytical procedure used in laboratory medicine, mining, pharmacology, and environmental biology to quantitatively or qualitatively measure the presence of substances (called analytes) in organic samples such as humans, animals, soil, minerals, water, or plants. An analyte in an organic or inorganic sample may include anything from drugs and biochemical substances to chemical elements or compounds, cells, organisms, and microorganisms in either an organic or inorganic sample. Assaying these samples involves performing an assay using either biological or chemical techniques that detect and decipher signals produced by an analyte in order to provide results. Results may include values such as concentration in milligrammes per deciliter (mg/dl), percentage, enzyme international units, or qualitative or semiquantitative readouts such as colour changes, conductivity variations, luminescence changes, or an increase or decrease in activity of an enzyme or biochemical reaction activity.
Qualitative assays can provide more sensitive results than chemical analyses without providing an exact number for the analyte being assessed. They tend to be less precise due to interference from other substances present in a sample, such as metal ions or compounds; however, many qualitative tests are designed specifically to avoid such interference.
Quantitative assays used for qualitative analyses include the reagent diffusion test, the microslide plate agglutination assay, and the radial immunodiffusion assay. These latter two techniques are used to detect various cellular secretions, including antibodies, cytokines, and lectins, without needing special equipment in any microbiological laboratory.
Some assays utilise multiple techniques to increase their sensitivity. For instance, the ELISA and RIA techniques employ antibodies and chromogenic substrates to detect and quantify antigens; other amplification techniques, including electrophoresis and chromatography, may also be utilised to increase an assay’s sensitivity.
Qualitative research is an inquiry-based approach to inquiry that gathers and studies data in an open-ended fashion by asking questions such as “why” rather than “how many” or “how much.” An investigative approach designed to collect qualitative data aims to shed light on real-world phenomena and processes that cannot easily be measured quantitatively, such as social interactions and processes that occur outside of lab environments. It can either be undertaken as an independent investigation or in combination with quantitative research studies. Qualitative studies may be used to generate hypotheses that can then be tested through more quantitative means, such as an experiment or survey. Once collected, data from qualitative studies can then be analysed more statistically significantly than would otherwise be possible using only quantitative information.