Allergen-specific Lateral Flow Devices
Ever wondered why rapid on-site testing systems are called "kits." The term is used because these kits provide all necessary components in a ready-to-use format for conducting a specific number of tests.
The episode focuses on allergen-specific lateral flow devices, also known as dipstick tests. These are qualitative or semi-quantitative immunochromatographic tests based on the ELISA technique.
What’s in the Kit?
Each kit typically includes:
- Sterile surface swabs
- Extraction and dilution buffers
- Test strips
- Disposable pipettes, scoops, and sampling bowls
Additional recommended tools for accuracy and contamination prevention:
- Disposable gloves
- Electronic scale
- Sample grinding tool
- Ethanol for bench cleaning
How Are These Tests Conducted?
There are four main steps:
- Sampling – Collecting environmental swabs, rinse water, or product samples (rinse water should be free of detergent or sanitizer residue).
- Sample Preparation & Protein Extraction – Mixing the sample with extraction buffer and shaking it manually or using a heated water bath for complex food samples.
- Testing – Applying the prepared sample to the test strip.
- Result Interpretation – Analyzing the test and control lines for allergen presence.
Understanding the Test Strip
The test strip has four zones:
- Sample Zone – Absorbs the sample extract.
- Conjugate Zone – Contains allergen-specific antibodies bound to latex or metal particles, forming an allergen-antibody complex.
- Test Zone – A second set of allergen-specific antibodies binds to the complex, creating a visible test line. The line’s intensity correlates with allergen concentration.
- Wick Zone – Acts as a reservoir for excess sample.
The control line ensures the test is valid.
Potential Weaknesses of These Tests
- Hook Effect – Extremely high protein concentrations can cause false negatives; dilution and retesting are recommended.
- Matrix Interference – Components like fats and polyphenols can hinder protein extraction.
- Allergen Residue Nature – Food processing can alter protein structures, making allergens harder to detect.
Conclusion
Allergen-specific lateral flow devices are valuable tools for verifying cleaning efficacy and screening raw ingredients but must be used carefully. The next episode will cover total protein indicator kits.
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