Initial assessment
Given a clinical history suggestive of allergic disease, structured screening is initiated. Consider respiratory/ocular symptoms (asthma, rhinitis, conjunctivitis), food-related manifestations (abdominal pain, vomiting, diarrhoea/diarrhea, feeding refusal, failure to thrive, eczema), and reactions to drugs, latex, and Hymenoptera venoms. Confirm the temporal relationship with exposure and consider differential diagnoses.
Skin prick testing (prick test)
If available and not contraindicated, the prick test is the first step. A positive result, when consistent with the history, confirms sensitisation and guides allergen avoidance and, where indicated, immunotherapy. If negative but clinical suspicion persists, proceed with specific IgE testing. When the prick test is unavailable or contraindicated, prefer laboratory tests.
When to avoid the prick test
Avoid when antihistamines/tricyclic antidepressants must be continued, in extensive dermatoses/dermographism, or where there is a high risk of anaphylactic reaction to the allergen. In these scenarios, use serum specific IgE.
Specific IgE panels (laboratory screening)
Phadiatop (inhalants): mixture of mites, animal dander, moulds and pollens; useful for screening respiratory atopy.
Fx5 (foods): mixture of common food allergens (e.g., egg, milk, fish, wheat, peanut, soya/soy); useful for screening food allergy. Reporting is qualitative/semi-quantitative with a usual threshold of 0.35 PAU/l.
Panel interpretation
Values above the threshold suggest atopy/sensitisation; increasing classes (1–6) reflect higher clinical likelihood. A positive panel guides selection of individual specific IgE by allergen group. A negative panel with strong clinical suspicion requires reassessment (other diagnoses, seasonal repeat testing, or an alternative method).
Individual specific IgE — indications
Order to: confirm diagnosis when history is compelling; guide avoidance measures; when the prick test cannot be performed; prick test negative with high suspicion; confirmation prior to immunotherapy; monitoring tolerance (food allergy) or response to desensitisation. Select 1–2 allergens per group, tailored to history and epidemiological context.
Total IgE — when to order
Not indicated for routine screening of respiratory or food allergy. Reserve for specific situations: assessment/follow-up of allergic bronchopulmonary aspergillosis, determination of initial omalizumab dose, and hyper-IgE syndromes.
Conclusion
Recommended pathway: clinical history ➝ prick test (if possible) ➝ screening IgE panels (Phadiatop/Fx5) ➝ individual specific IgE as indicated; reserve total IgE for particular cases. This sequence standardises diagnosis, avoids indiscriminate testing, and supports decisions on avoidance and immunotherapy.
