Summary of the evidence
This SR of 149 diagnostic accuracy studies comprising 24,489 patients
with suspected IgE-mediated FA shows that many IgE sensitization tests
to suspected food triggers can support the diagnosis of IgE-mediated FA.
Our findings favour the use of SPT and sIgE testing in clinical settings
in the diagnosis of FA, especially for peanut, HE, CM, and tree nut
allergies for which there is more evidence and their diagnostic accuracy
is higher. Their high sensitivity means a negative test is useful for
ruling out food allergy. Conversely, SPT and sIgE are less accurate in
supporting the diagnosis of sesame, soy, wheat and shrimp allergies with
moderate certainty of evidence.
High certainty of evidence for the diagnostic accuracy of CRD for ruling
in food allergy (high specificity) has been demonstrated for several
allergen components, namely: Ara h 2 in peanut, Cor a 14 in hazelnut and
Ana o 3 in cashew. Ovomucoid can support the diagnosis of raw and cooked
HE allergies whilst casein can support diagnosis of CM allergy; however,
the accuracy of these allergen components is not superior to the
allergen extracts. Current diagnostic tests (SPT, specific IgE to
extracts or components) do not accurately reflect a subject’s ability to
tolerate baked foods and there is limited evidence on test accuracy for
baked HE and baked CM allergies.
There is high certainty of evidence for the ability of BAT to diagnose
peanut and sesame allergies, particularly in cases where the clinical
history and results of other diagnostic tests are inconclusive. BAT had
very good diagnostic performance, but is not widely available in
clinical practice and the interpretation of BAT results can be complex
and require expert knowledge.
It is important to note that the accuracy of these diagnostic tests may
vary depending on the individual being tested and the specific allergen
being evaluated. Diagnostic tests should always be interpreted in the
context of the patient’s pre-test probabilities (likelihood of having an
FA before being tested) which is influenced by the medical history,
co-morbidities and symptoms of presentation. There is also inherent
variability in the diagnostic methods employed, particularly in the case
of SPTs, the specific technique, individual performing the test,
reagents and equipment used locally can potentially impact the outcomes.
There can also be variability within subjects with the site of testing,
time of day, temperature, exercise prior to testing, etc. To ensure
comprehensive coverage in our analysis, we included studies utilizing a
range of commercial extracts. It is important to consider that including
studies which used different SPT reagents or methods may have influenced
the results [181]. These variations become particularly significant
when dealing with allergens that lack standardization, such as fish
[182] and shellfish [183].
Due to limited data available, we were unable to conduct a thorough
meta-analyses on some food allergies, such as LTP-related food allergy,
fish or shellfish allergies. For allergy tests not included in the SR
there is insufficient evidence on the accuracy of that test for
diagnosing IgE-mediated FA and no conclusions can be made on the
certainty of evidence for its use in clinical practice.