LABUPDATE no. 38 version 3
March 2025
INTRODUCING THE ALEX2 TEST
The diagnosis of an allergy involves thorough history taking and diagnostic blood, skin prick and/or provocation tests.
Blood tests can be divided into IgE-mediated and non-IgE-mediated tests. Blood tests for specific IgE antibodies against
allergens are safe and do not require medication to be withdrawn prior to testing. The IgE-mediated blood tests consist
of screening panels (Phadiatop inhalant and food mix IgE) and specific IgE tests directed at individual allergen extracts
with or without allergen molecular components.
The Allergy Xplorer (ALEX2) is a multiplex IgE immunoassay in the form of a chip-based macroarray. It contains both whole
allergen extracts and molecular allergen components. This multiplex allergy tests simultaneously measures multiple allergens
in one test. It is a cost-effective way to examine IgE sensitisation patterns, especially in patients with complex symptoms,
poly-sensitisation and high levels of total serum IgE. Although similar to the Immuno Solid-Phase Allergen Chip (ISAC) test,
there are key differences, including the number of allergens offered and the decreased cost per allergen (Table 1). The use
of a cross-reactive carbohydrate determinants (CCD) inhibitor reduces the reporting of clinically irrelevant cross-reactivity.
TABLE 1: COMPARISON OF THE ALEX2, ISAC E112iTM AND PHADIATOP/FOOD MIX lGE ALLERGEN TESTS
ALEX2
ISAC E112iTM
Phadiatop (inhalants) and food mix (Fx5) IgE
screens with breakdown allergens
Number of IgE
allergens tested
~300 whole extract allergens and
allergen components
112 allergen components
Phadiatop screen and food mix screen
with 15 whole extract allergens in the breakdown
Types of allergens
tested
Food, inhalants, latex, insect venom
and cross-reactive components
Food, inhalants, latex and cross-
reactive components
Food and inhalants
CCD inhibitor used Yes No No
Turnaround time* ~7 working days ~7 working days 24 hours
Sample requirements 0.5 ml SST (serum) tube 0.5 ml SST (serum) tube 5 ml SST (serum) tube
Mnemonic ALEX ISAC (replaced by ALEX) PHAD + PED
* Once received at the National Reference Laboratory.
GROUPS OF ALLERGENS TESTED WITH ALEX2:
INHALANTS
• Pollen
• House dust mite and
storage mite
• Pets e.g. dog, cat,
guinea pig, mouse,
hamster and rabbit
• Farm animals e.g.
pig, sheep, horse
and cow
• Mould and yeast
• Cockroach
FOOD
Plant-based
• Nuts and tree nuts e.g. cashew, Brazil nuts, pecan,
hazelnut, walnut, macadamia, pistachio and almonds
• Legumes e.g. peanut, soy, chickpea, lentils, white
bean and pea
• Seeds e.g. pumpkin, sunflower, poppy and sesame
• Cereals e.g. oats, quinoa, rice, wheat and maize
• Spices e.g. mustard seed, oregano and parsley
• Vegetables e.g. onion, carrot, tomato, potato, celery
and garlic
• Fruit e.g. peach, apple, banana, strawberry, kiwi,
papaya and fig
Animal-based
• Milk e.g. cow, camel, goat, mare and sheep
• Egg white and egg yolk
• Meat e.g. cow, chicken, turkey, lamb and pork
Seafood
• Cod, crab, oyster, mussel,
salmon, squid and prawn/shrimp
Edible insects
• Mealworms, crickets and locust
VENOMS
• Ant, bee and wasp
OTHER
• Latex
Note: These are examples of allergens detected with ALEX2 and is not an exhaustive list of allergens included in the test panel.
INTERPRETATION OF ALEX2 ALLERGEN RESULTS
A personalised, user-friendly and interpretive report, outlining individual allergy profiles with relevant supporting information
will be provided.
CONCLUSION
The ALEX2 test has replaced the ISAC test and aims to improve allergy management through accurate and affordable
IgE-mediated allergy diagnosis and risk assessment. Once a diagnosis has been made, the selection of appropriate
allergen avoidance strategies, medical therapy and/or immunotherapy will help improve patients’ symptom control
and quality of life.
For more information, contact the NRL Immunology Laboratory at 012 678 0613/4.
ampath.co.za