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.

Background Single nucleotide polymorphisms (SNPs) in the interleukin 13 (IL13) gene are associated with vulnerability to allergic diseases, such as asthma and allergic conjunctivitis (AC). Periostin, as an IL13-induced protein, has emerged as a novel biomarker in several allergic diseases. Data among Egyptian patients are still scarce. Aim To find out the association of IL13 rs20541 gene polymorphism and serum levels of periostin with asthma and AC among Egyptian patients. Patients and Methods Eighty-one Egyptian allergic patients with asthma, AC, and both asthma and AC (27 each), were enrolled in this case–control study. Twenty-seven age and gender-matched healthy volunteers served as controls. All participants were tested for IL13 rs20541 SNP by real-time polymerase chain reaction, TaqMan method. Serum levels of periostin and IL13 were assessed by ELISA. Results Compared to healthy subjects, asthmatic patients had a higher frequency of the homozygous adenine/adenine (AA) genotype at IL13 rs20541 SNP (14.8% vs 3.7%) and a lower frequency of the guanosine/guanosine (GG) genotype (51.9% vs 55.6%), while AC patients had higher GG genotype (70.4% vs 55.6%) with no AA genotype detected, yet no significant difference was noticed (p = 7.053). A significantly higher serum periostin in asthmatic patients compared to controls was found (p = 0.005). Higher levels of serum periostin, although nonsignificant, were recorded in AC patients compared to controls (22.88 ± 10.01ng/mL and 17.51 ± 3.17ng/mL, respectively). Periostin was significantly higher in patients with IL13 AA and GA genotypes compared to those with GG genotype (p = 0.016). A significant positive correlation between serum periostin and serum IL13 among allergic patients was recorded (r = 0.352, p < 0.001). Conclusion Among Egyptian patients, serum level of periostin is significantly associated with asthma and positively correlates with IL13 level supporting its utility as a diagnostic biomarker. IL13 rs20541 gene polymorphism does not seem to play an obvious role in asthma and AC, which requires further evaluation.