The ALEX3 allergy blood test screens for IgE sensitisation to 295 allergens from a single blood draw — the most comprehensive allergy panel currently available in the UK. When your results arrive, you'll receive a detailed report showing which allergens have triggered an IgE response and at what level.
For many patients, this can feel overwhelming. A long list of positive results doesn't necessarily mean you have a clinical allergy to all of them — and understanding the difference between sensitisation, cross-reactivity, and true allergy is essential for interpreting your results correctly and deciding what to do next.
How to Read Your ALEX3 Report
Your ALEX3 results are reported as IgE levels for each allergen, typically in kUA/L (kilounits of allergen per litre). The standard classification bands are:
| IgE Level (kUA/L) | Class | Clinical Significance |
|---|---|---|
| < 0.10 | Class 0 | No detectable sensitisation — negative result |
| 0.10 – 0.34 | Class 1 | Very low sensitisation — unlikely to be clinically relevant |
| 0.35 – 0.69 | Class 2 | Low sensitisation — possible mild sensitivity |
| 0.70 – 3.49 | Class 3 | Moderate sensitisation — clinically relevant in many patients |
| 3.50 – 17.49 | Class 4 | High sensitisation — significant clinical relevance likely |
| 17.50 – 49.99 | Class 5 | Very high sensitisation |
| > 50.0 | Class 6 | Very high sensitisation — strong clinical relevance |
Sensitisation vs Clinical Allergy — The Critical Distinction
Up to 30% of the general population are sensitised to at least one common allergen on IgE testing — but a much smaller proportion have clinically relevant allergies that cause symptoms on exposure. Sensitisation is a necessary but not sufficient condition for clinical allergy.
A result should be interpreted as clinically relevant when:
- The IgE level is Class 3 or above (≥0.70 kUA/L)
- You have a history of symptoms consistent with exposure to that allergen
- The symptoms are reproducible on repeated exposure
- The sensitisation pattern is consistent with your symptom profile (e.g. grass pollen sensitisation + seasonal rhinitis in spring/summer = consistent)
Class 1–2 results (0.10–0.69 kUA/L) should be interpreted with caution and in the context of your symptoms. Many Class 1–2 positives reflect cross-reactivity rather than primary sensitisation.
Understanding Cross-Reactivity
One of the most important concepts in interpreting ALEX3 results is cross-reactivity. Many allergen proteins share structural similarities — so if your immune system is sensitised to one protein, it may also react to structurally similar proteins in different sources without you being truly allergic to them.
Common cross-reactive patterns include:
| Primary Sensitisation | Common Cross-Reactive Positives | Clinical Relevance |
|---|---|---|
| Birch pollen (Bet v 1) | Apple, pear, cherry, peach, carrot, celery, hazelnut, soy | Oral allergy syndrome (mild mouth tingling) — rarely severe |
| Grass pollen | Some cereals, tomato | Usually low clinical relevance for food reactions |
| Latex | Banana, avocado, kiwi, chestnut | Potentially clinically relevant — latex-fruit syndrome |
| Cat/dog epithelium | Pork (pork-cat syndrome) | Relevant in some patients |
| House dust mite | Shellfish (tropomyosin) | Usually low clinical relevance for seafood reactions |
The ALEX3 test specifically includes molecular allergen components (CRD — component-resolved diagnostics) that help distinguish primary sensitisation from cross-reactivity. Your GP will review these alongside your symptom history to determine which results are clinically meaningful.
What to Do Based on Your Results
If You Have High-Level Sensitisation (Class 4–6) to a Food Allergen
- Discuss strict avoidance with your GP — particularly if you have a history of anaphylaxis or severe reactions.
- Your GP may recommend an adrenaline auto-injector (EpiPen) prescription if there is a risk of severe reaction.
- Allergen-specific immunotherapy (desensitisation) may be an option for certain allergens — your GP can refer to an NHS or private allergy specialist for assessment.
If You Have High-Level Sensitisation to Environmental Allergens
- House dust mite: HEPA air purifiers, allergen-proof mattress covers, washing bedding at 60°C, reducing carpets and soft furnishings.
- Grass/tree pollen: tracking pollen forecasts, avoiding outdoor exercise on high-pollen days, showering after outdoor exposure, nasal filters.
- Cat/dog epithelium: if pet removal isn't practical, HEPA filtration and regular bathing of pets can reduce indoor allergen load.
- Consider allergen immunotherapy (AIT) — the only disease-modifying treatment for environmental allergies. Discuss referral with your GP.
If You Have Mostly Low-Level Results (Class 1–2)
- Do not make unnecessary dietary eliminations based on Class 1–2 results alone — the evidence that these cause clinical symptoms is limited, and elimination diets carry nutritional risks.
- If you have unexplained symptoms, keep a symptom diary noting exposures and reactions. Bring this to your GP review appointment for contextual interpretation.
The GP Review — Why It Matters
At Lambert Medical, every ALEX3 result is reviewed by a GP alongside your clinical history and symptom profile. The test data alone is not sufficient for clinical decision-making — a patient with a Class 5 peanut result who has eaten peanuts for years without symptoms requires a very different clinical response to one who has had anaphylaxis.
Your GP review appointment will cover:
- Which results are clinically relevant given your symptom history
- Avoidance recommendations where appropriate
- Whether any results warrant referral to an allergy specialist
- Environmental control measures for airborne allergens
- Whether an adrenaline auto-injector is appropriate
- Discussion of immunotherapy options if relevant