Lateral-Flow Immunochromatographic Assay
Definition
A rapid, single-use immunoassay format in which sample extract migrates along a nitrocellulose membrane past a detection zone loaded with antigen-specific antibody conjugated to colloidal gold. A visible coloured line forms at the test zone if the target antigen is present above the detection threshold.
- Format
- Rapid, single-use immunoassay
- Medium
- Nitrocellulose membrane
- Label
- Colloidal gold-conjugated antibody
- Result readout
- Visible coloured line at the test zone
Common questions
Why are lateral-flow tests used as a presumptive step rather than a final identification in forensic casework?+
The visible line confirms the target antigen is present above a threshold but does not by itself rule out cross-reactivity with related proteins from other species or sources. Positive results are typically followed by a confirmatory laboratory method before a finding is reported as conclusive.
What can cause a false negative on a lateral-flow immunochromatographic test?+
Very high antigen concentration can saturate the capture zone and produce a weak or absent line, a phenomenon known as the hook effect, as can degraded samples, expired reagents, or an antigen concentration below the assay's detection threshold. Running a diluted retest can resolve a suspected hook effect.
Related terms
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Explained in these topics
- Immunological Confirmatory Tests for Human BloodA format in which a liquid sample migrates along a nitrocellulose membrane by capillary action past zones containing antibodies. A colour change at the test li...
- Immunological Identification of Semen and Saliva