Enzyme-Linked Immunosorbent Assay (ELISA)
Enzyme-Linked Immunosorbent Assay · Also known as: enzyme immunoassay, EIA, solid-phase enzyme immunoassay, ELISA test
ELISA is a plate-based immunoassay technique that detects and quantifies proteins, antibodies, antigens, hormones, and other analytes in biological samples. Widely used in veterinary science, medicine, and food safety, it exploits the specificity of antibody–antigen binding coupled to an enzyme-driven colorimetric signal to deliver sensitive, reproducible measurements across large sample batches.
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When to use it
ELISA is the method of choice when you need to detect or quantify a specific protein, antibody, or small molecule across a large number of biological samples with high sensitivity and throughput. In veterinary science it is routinely used for seroprevalence surveys, vaccine efficacy monitoring, disease diagnosis (e.g., brucellosis, bovine viral diarrhea, avian influenza), and hormone profiling. It is not appropriate when the target lacks a validated antibody pair, when samples are highly complex matrices that cannot be adequately diluted or pre-treated, or when single-molecule sensitivity below ELISA's detection limit is required (consider PCR or mass spectrometry instead).
Strengths & limitations
- High sensitivity — detection limits typically in the pg/mL to ng/mL range — suitable for low-abundance targets in clinical samples.
- High throughput — a single operator can process 96 or 384 samples simultaneously on a standard microplate format.
- Quantitative output — a standard curve allows interpolation of absolute analyte concentrations, not just presence/absence.
- Relatively low cost per sample compared to mass spectrometry or biosensor platforms.
- Robust and well-validated — decades of published reference ranges and commercial kit availability for most veterinary pathogens.
- Adaptable format — direct, indirect, sandwich, and competitive ELISA variants cover antigens, antibodies, haptens, and hormones.
- Requires validated antibodies; cross-reactivity with related antigens can yield false positives, especially across species.
- Cannot differentiate between viable and non-viable pathogens — detects antigen or antibody, not infectivity.
- Matrix effects from lipemia, hemolysis, or high protein content in complex samples can suppress or enhance signal.
- Standard curves must be run on every plate; inter-plate variability requires careful normalization for multi-plate studies.
- Cannot multiplex many targets simultaneously without specialized platforms (e.g., Luminex bead-based arrays).
Frequently asked
What is the difference between sandwich ELISA and competitive ELISA?
In sandwich ELISA, two antibodies bind the target simultaneously — one captures it on the plate surface and a second (detection) antibody binds a different epitope, amplifying signal. Signal increases with analyte concentration. In competitive ELISA, sample analyte and a labeled analyte compete for a limited number of antibody binding sites; signal decreases as analyte concentration increases. Sandwich ELISA is preferred for large proteins; competitive ELISA is necessary for small molecules (haptens, hormones, mycotoxins) that cannot accommodate two antibody binding sites.
How sensitive is ELISA compared with PCR?
ELISA detects protein or antibody, typically at pg/mL to ng/mL concentrations, whereas PCR detects nucleic acid and can in principle detect a single copy of a target sequence. For active infection early in the incubation period, PCR is more sensitive. For serodiagnosis — detecting the host's antibody response — ELISA is the standard tool because PCR does not detect antibodies. The two methods are complementary rather than interchangeable.
Can I use a kit validated for one species in a different species?
Not without verification. Commercial kits are typically validated for a defined host species using species-specific secondary antibodies and matrix-matched standards. Cross-species application can fail due to differences in immunoglobulin structure or matrix composition. Always check the kit datasheet, run a parallelism experiment (serial dilutions of the new species' sample should produce a curve parallel to the standard curve), and if possible validate against a reference method.
What causes a high background signal in my ELISA?
The most frequent causes are insufficient blocking, inadequate washing, over-incubation of the detection antibody or substrate, and non-specific binding of the secondary antibody to the plate. Check that your blocking buffer is appropriate for the antibody host species (BSA is unsuitable if the detection antibody was raised in bovine), extend wash steps, reduce detection antibody concentration, and shorten substrate incubation time. Running a no-primary-antibody control helps isolate which step is generating background.
Sources
- Engvall, E., & Perlmann, P. (1971). Enzyme-linked immunosorbent assay (ELISA) quantitative assay of immunoglobulin G. Immunochemistry, 8(9), 871–874. DOI: 10.1016/0019-2791(71)90454-X ↗
- Crowther, J. R. (2001). The ELISA Guidebook. Humana Press. ISBN: 978-0896036093
How to cite this page
ScholarGate. (2026, June 3). Enzyme-Linked Immunosorbent Assay. ScholarGate. https://scholargate.app/en/veterinary-science/elisa
Which method?
Set this method beside its closest kin and read them side by side — the library lays the books on the table; the choice is yours.
- Flow CytometryPharmacology↔ compare
- RadioimmunoassayVeterinary Science↔ compare