Introduction: Skin prick test (SPT) is the most sensitive and reliable method of detecting the causative allergens and considered the gold standard method for allergy testing, it is also simple, quick and cheap. However it has an invasive nature requires multiple skin pricks, painful for children and difficult if skin diseases coexist. SPT can be affected by antihistaminics and corticosteroids. Hence, an immunoblotting technique as an alternative test for IgE determination has been developed, which is lesser invasive. Aim: To evaluate the immunoblot test by comparing it to SPT in diagnosis of allergic conjunctivitis. Patients and Methods: Immunoblot test was done for 32 patients clinically diagnosed as allergic conjunctivitis, either alone or associated with allergic rhinitis and / or bronchial asthma and who gave positive SPT
with one or more of 11 natural allergenic extracts. Results: Overall diagnostic performance of immunoblot test in comparison to SPT for detection of all studied aeroallergens showed 27.5% sensitivity, 98.0% specificity, 97.0% positive predictive value, 33.2% negative predictive value and 46.2% diagnostic accuracy. Conclusion: Since immunoblotting technique has low sensitivity and high specificity, hence it can be used as confirmatory test secondary to SPT for
diagnosis of causative allergens.