Conjunctival allergen challenge:: practical recommendations for the diagnosis of allergic conjunctivitis.: Report (proceedings) of the meeting of the Group Ophthalmo Allergo (Journees parisiennes d'allergie, January 10, 2004)

Conjunctival allergen challenge (CAC) is the only way to confirm allergen involvement in the diagnosis of allergic conjunctivitis. Implementation of CAC for diagnostic purposes was the subject of a round table discussion during the last meeting of the Group ophthalmoallergo. The main conclusions of the discussion are reported here. After a brief review of the indications for CAC, the group discussed different aspects of CAC: criteria for the diagnosis of sensitisation; safety considerations; the nature and quality of the allergen extracts used; the possibility of avoiding responsible allergens and drugs; contraindications. A consensus was reached regarding the practice of CAC for the diagnosis of allergic conjunctivitis, the dose escalation protocol for allergen instillation, the clinical as well as the complementary criteria for positivity, and interpretation of the results. The group agreed on the need to consider two distinct patient populations, outpatients and inpatients, according to the CAC technique to be used and the follow-up to be considered. Outpatients usually have benign forms of allergic conjunctivitis (acute and seasonal or chronic) due to common allergens (mainly domestic allergens and aeroallergens). In these patients, CAC can be carried out in a medical environment, with an allergist or an ophthalmologist being present, in which case escalation of the allergen dose instilled in the conjunctivae can be rapid and positivity can be assessed by evaluating the pruritus only. Inpatients, affected mainly by vernal keratoconjunctivitis, will have to undergo a more detailed investigation to identify the triggering factor. In these cases, CAC should be carried out by an ophthalmology service. The clinical and biological criteria for positivity are multiple, and a wider variety of allergens may be tested, using a slower dose escalation. In both types of patients, 20 muL of the allergen are instilled every 30 minutes, and the reaction is assessed 15 minutes after each instillation. Emergency measures, including an oral histamine H1 antagonist, an inhalation bronchodilator, and topical and systemic steroids, must be available. Patients must be observed closely until the procedure is completed. If an ocular reaction occurs, an antihistamine should be instilled locally and the patient followed for an additional two hours. In addition, a topical and an oral antihistamine should be prescribed to be used in case the patient has a conjunctival or systemic reaction after discharge. These national guidelines should help practitioners to standardize CAC. They will be reevaluated in three years. (C) 2004 Elsevier SAS. Tous droits reserves.