Fluorescence Immunoassay (FIA)
What it is
Fluorescence immunoassay uses a fluorescent label instead of colloidal gold and is read by a dedicated analyzer, producing quantitative (not just qualitative) results.
How it works
A fluorescent conjugate binds the analyte and is captured at the test line; a fluorescence analyzer measures the emitted signal intensity, which is converted to a concentration via a calibration curve.
Why it matters
FIA upgrades rapid tests from qualitative triage to quantitative measurement — relevant for cardiac markers, hormones and inflammation markers where a numeric result adds clinical value.
Key components
- Fluorescent label (e.g., europium/fluorescent microspheres)
- Fluorescence analyzer (reader)
- Calibration curve for quantification
Applications
- Quantitative cardiac and inflammatory markers (troponin, CRP, PCT)
- Quantitative hormone assays
- Semi-quantitative infectious-disease markers
What affects performance
- Fluorophore brightness and stability
- Reader calibration
- Background fluorescence
- Conjugate uniformity
Limitations
- Requires a reader instrument
- Higher cost than visual formats
- Reader calibration and QC are required
Frequently Asked Questions
What is fluorescence immunoassay (FIA)? An immunochromatographic assay using fluorescent labels and a reader to produce quantitative or semi-quantitative results.
How does FIA differ from visual lateral flow? It uses fluorescent labels read by an instrument, enabling quantification instead of naked-eye line reading.
Related knowledge
References
- Sajid M, Kawde AN, Daud M. Designs, formats and applications of lateral flow assay. J Saudi Chem Soc. 2015;19(6):689-705.
- Koczula KM, Gallotta A. Lateral flow assays. Essays Biochem. 2016;60(1):111-120.
- Bahadır EB, Sezgintürk MK. Lateral flow assays: principles, designs and labels. TrAC Trends Anal Chem. 2016;82:286-306.
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Written by the Progene Bio Technical Team · Last reviewed: 2026-09-12