Lateral-Flow Immunoassay
Definition
A point-of-care competitive immunochromatographic format on a nitrocellulose strip. In the absence of drug, colloidal gold-labelled antibody is captured at a test line, producing a visible band. In the presence of drug at or above the cut-off concentration, sample drug saturates the antibody and prevents test-line capture, so the line disappears. A missing test line equals a positive result.
- Result time
- Minutes (visible line forms rapidly)
- Core material
- Nitrocellulose strip with colloidal-gold antibody conjugate
- Test format
- Sandwich or competitive immunoassay on a card strip
- Replaced
- Earlier tube-based precipitin tests in modern serology
Common questions
How does a lateral-flow immunoassay test show a result?+
A stain extract or body fluid sample wicks across a nitrocellulose strip. As it moves through antibody-conjugate zones, a colored line appears within minutes if the target antigen is present. The visible line confirms a positive result without need for laboratory equipment.
What are common uses of lateral-flow tests in forensics?+
These tests are used in point-of-care drug screening (urine drug strips and NDPS field kits), as well as rapid serology testing. Pregnancy tests and COVID-19 tests use the same technology. They are valued for quick on-scene or bedside results.
Why did lateral-flow tests replace older serology methods?+
Lateral-flow tests replaced earlier tube-based precipitin tests because they are faster, simpler, and require less equipment. This makes them practical for field work and emergency settings.
Related terms
- Precipitin Test
- A serological method in which an antiserum specific to one species' proteins is mixed with an extract of an unknown specimen. Formation...
- ELISA (Enzyme-Linked Immunosorbent Assay)
- A plate-based immunoassay format in which a target antigen is captured by an antibody bound to a solid surface, detected by a...
- Antigen
- A molecule recognised by the adaptive immune system through specific binding to an antibody or T-cell receptor. Defined by immunogenicity (capacity to...
- Cross-Reactivity
- The capacity of an antibody raised against one analyte to bind structurally related compounds. In RIA, cross-reactivity is the main driver of...
- Monoclonal Antibody
- An antibody produced from a single B-cell clone, recognising a single specific epitope. In forensic species identification, monoclonal antibodies offer higher specificity...
- Secretor Status
- A genetic trait that determines whether a person expresses their ABO blood group antigens in secreted body fluids such as saliva, semen,...
- ABO Blood Group System
- Classification of red blood cells by the presence or absence of A and B antigens on the cell membrane, determined by alleles...
- ABO System
- The blood-group classification described by Karl Landsteiner in 1901: groups A, B, AB, and O, defined by antigens on red-cell surfaces and...
- Antibody
- An immunoglobulin (typically IgG) raised to bind a specific antigen. Source decides specificity: polyclonal antibodies recognise many epitopes, monoclonal antibodies recognise one.
- Antibody (Immunoglobulin)
- A Y-shaped glycoprotein produced by B lymphocytes that binds a specific antigen at its variable regions. Antibodies used as forensic reagents are...
- Antigen-Antibody Reaction
- The specific non-covalent binding between an antigen (a molecule capable of eliciting an immune response) and the antibody produced against it. In...
- CEDIA (Cloned Enzyme Donor Immunoassay)
- A homogeneous immunoassay using two inactive fragments of beta-galactosidase, an enzyme donor (ED) fragment conjugated to drug, and an enzyme acceptor (EA)...
Explained in these topics
- History of Forensic Serology and Immunological MethodsA membrane-strip device in which a sample migrates by capillary action past labelled antibody zones. Binding of the target antigen produces a visible coloured...
- Immunoassays in Forensic Science: Principle, Types, Techniques and ApplicationsThe rapid-test card format (point-of-care urine drug strips, NDPS field kits, pregnancy and SARS-CoV-2 tests). A competitive or sandwich immunoassay run on a n...
- Immunological Drug Testing: Screening and Forensic InterpretationA point-of-care competitive immunochromatographic format on a nitrocellulose strip. In the absence of drug, colloidal gold-labelled antibody is captured at a t...
- The Role of Immunology in Forensic ScienceA rapid point-of-collection immunoassay format in which sample migrates along a nitrocellulose membrane past coloured antibody conjugates and capture lines. A...
- Immunological Testing in Wildlife Crime and Food Fraud InvestigationsA dipstick or strip format in which sample fluid migrates along a nitrocellulose membrane, encounters labelled antibodies, and produces a visible test line if...
- Scope and History of Forensic SerologyA rapid, card-based test in which a stain extract wicks through a membrane past antibody-conjugate zones; a visible line forms within minutes if the target ant...
- Scope of Forensic Immunology: Specimens and ContextsA rapid, portable, membrane-based assay in which a sample migrates along a nitrocellulose strip past immobilised antibody capture zones. A visible line at the...