Sensitisation to Common Environmental Respiratory Allergens in Karachi

To identify sensitisation to common environmental allergens among patients with allergic rhinitis and allergic asthma in Karachi and to assess the agreement between skin prick testing (SPT) and allergen-specific immunoglobulin E (IgE) immunoblotting.

A descriptive cross-sectional study. Place and Duration of the Study: Department of Immunology, the Indus Hospital and Health Network, Karachi, Pakistan, from April to December 2025.

Sixty-four patients with allergic rhinitis and/or allergic asthma were included. Demographic and clinical data were collected using a structured questionnaire. Participants underwent SPT. Wheals ≥3 mm larger than negative controls were considered positive. Serum allergen- specific IgE was measured using the Euroimmun immunoblot assay, with levels ≥0.35 kU/L considered indicative of sensitisation. Absolute eosinophil counts and total IgE levels were recorded. Data were analysed using SPSS version 21. Chi-square or Fisher's exact tests were used to assess categorical variables, McNemar's test was used to compare paired positivity, and Cohen's kappa was used to assess agreement. A p-value of <0.05 was considered statistically significant.

Of 64 patients (mean age, 31.1 ± 14.1 years; 32 [50.0%] females), 56.3% (n = 36) showed sensitisation to at least one allergen on SPT, compared with 68.8% (n = 44) on immunoblot. The most common allergens identified on SPT were raw cotton (18.8%, n = 12) and cannabis (17.2%, n = 11). Immunoblot showed sensitisation to Dermatophagoides (D.) pteronyssinus (28.1%, n = 18) and D. farinae (25.0%, n = 16), followed by weed pollens (mix 1) and German cockroach, each at 14.1% (n = 9). Eosinophilia was present in 18 (28.1%) patients, and high serum total IgE was observed in 26 (40.6%). The difference in overall positivity between the two methods was not statistically significant on McNemar's test (p = 0.115), while their agreement was fair (κ = 0.344; p = 0.004).

Respiratory allergy in Karachi is characterised by diverse patterns of sensitisation. Sensitisation to house dust mites is predominant, while sensitisation to raw cotton and cannabis reflects common local exposures. SPT and allergen-specific IgE immunoblot showed fair agreement but identified differing sensitisation profiles.

Allergic rhinitis, Allergic asthma, Skin prick test, Allergen-specific IgE, Immunoblot, Sensitisation.