January 2024
Ampath | ampath.co.za
Overview
Diagnosing allergies requires:
- Thorough clinical history
- Diagnostic testing using:
- Blood tests
- Skin prick tests
- Provocation tests
Blood-based allergy tests fall into two categories:
- IgE-mediated tests
- Non-IgE-mediated tests
IgE-mediated blood tests are:
- Safe
- Do not require discontinuation of medication prior to testing
- Include:
- Screening panels (Phadiatop inhalant and food mix IgE)
- Specific IgE tests (whole allergen extracts ± molecular components)
What is ALEX2?
The Allergy Xplorer (ALEX2) is a multiplex IgE immunoassay using a chip-based macroarray.
Key features:
- Tests for ~300 whole allergen extracts and molecular components
- Detects IgE sensitisation patterns in one test
- Includes a CCD inhibitor to reduce false positives due to irrelevant cross-reactivity
- Suitable for patients with:
- Complex symptoms
- Poly-sensitisation
- High total serum IgE
The ALEX2 test has replaced the ISAC test.
Comparison of Allergy Tests
✅ ALEX2
- Tests: ~300 allergens (whole extracts + components)
- Types: Food, inhalants, latex, insect venom, cross-reactive components
- Uses CCD inhibitor: ✅ Yes
- Turnaround time: ~7 working days
- Sample: 0.5 mL serum (SST)
- Mnemonic:
ALEX - Price (2024): R3,958.96
✅ ISAC E112i™ (discontinued)
- Tests: 112 allergen components
- Types: Food, inhalants, latex, cross-reactive components
- Uses CCD inhibitor: ❌ No
- Turnaround time: ~7 working days
- Sample: 0.5 mL serum (SST)
- Mnemonic:
ISAC - Price (2023): R5,334.00
✅ Phadiatop + Food Mix IgE
- Tests: Phadiatop screen + food mix (15 whole extract allergens)
- Types: Food and inhalants only
- Uses CCD inhibitor: ❌ No
- Turnaround time: 24 hours
- Sample: 5 mL serum (SST)
- Mnemonics:
PHAD+PED - Price (2024): R5,622.32
Prices listed are for upfront payment and valid through 31 December 2024. Medical aid rates may differ.
Allergen Groups Covered by ALEX2
✅ Venoms
- Ant
- Bee
- Wasp
✅ Latex
✅ Plant-Based Allergens
Nuts and tree nuts:
- Cashew
- Brazil nuts
- Pecan
- Hazelnut
- Walnut
- Macadamia
- Pistachio
- Almond
Legumes:
- Peanut
- Soy
- Chickpea
- Lentils
- White bean
- Pea
Seeds:
- Pumpkin
- Sunflower
- Poppy
- Sesame
Cereals:
- Oats
- Quinoa
- Rice
- Wheat
- Maize
Spices:
- Mustard seed
- Oregano
- Parsley
Vegetables:
- Onion
- Carrot
- Tomato
- Potato
- Celery
- Garlic
Fruit:
- Peach
- Apple
- Banana
- Strawberry
- Kiwi
- Papaya
- Fig
✅ Animal-Based Allergens
Milk:
- Cow
- Camel
- Goat
- Mare
- Sheep
Egg:
- Egg white
- Egg yolk
Meat:
- Cow
- Chicken
- Turkey
- Lamb
- Pork
✅ Seafood
- Cod
- Crab
- Oyster
- Mussel
- Salmon
- Squid
- Prawn/Shrimp
✅ Edible Insects
- Mealworms
- Crickets
- Locusts
✅ Inhalants
Environmental:
- Pollen
- Mould and yeast
- Cockroach
Mites:
- House dust mite
- Storage mite
Pets:
- Dog
- Cat
- Guinea pig
- Mouse
- Hamster
- Rabbit
Farm animals:
- Pig
- Sheep
- Horse
- Cow
✅ Cross-Reactive Components
- CCD (Cross-reactive carbohydrate determinants)
- PR-10
- Profilin
- Lipid transfer protein (LTP)
- Serum albumin
- Parvalbumin
- Tropomyosin
- Storage proteins
- Lipocalins
This is not an exhaustive list of allergens tested by ALEX2.
Interpretation of Results
- Each patient receives a user-friendly, personalised report
- Reports include:
- Individual allergy profile
- Interpretive commentary
- Supporting clinical context
Conclusion
The ALEX2 test offers:
- A cost-effective, accurate tool for diagnosing IgE-mediated allergies
- Detection of clinically relevant sensitisation
- Risk assessment and allergen profiling to guide:
- Allergen avoidance
- Medical therapy
- Immunotherapy
Replacing the ISAC test, ALEX2 enhances allergy diagnosis and supports better long-term symptom control and quality of life.
📞 For more information, contact the NRL Immunology Laboratory at:
Tel: 012 678 0613 / 0614