Complexity of case mix in a regional allergy service

Currently in the United Kingdom (UK), there is a mismatch between limited financial resources and the large proportion of patients with suspected allergies actually being referred to specialist allergy clinics. To better understand the case mix of patients being referred, we audited referrals to a regional allergy service over an 8 year period.The main source of data was consultant letters to General Practitioners (GP) summarising the diagnosis of patients, archived from January 2002 to September 2009. Letters were reviewed, extracting the clinic date, doctor seen, gender, date of birth, postcode, GP, and diagnoses. Diagnoses were classified into seven groups and illustrative cases for each group noted.

Data from 2,028 new referrals with suspected allergy were analysed. The largest group of patients (43%) were diagnosed with a type I hypersensitivity. The other diagnostic groups were chronic idiopathic (spontaneous) urticaria (35%), suspected type I hypersensitivity but no allergen identified (8%), idiopathic (spontaneous) angioedema (8%), physical urticaria (2.5%), non-allergic symptoms (1.6%), type IV hypersensitivity (0.8%) and ACE inhibitor sensitivity (0.5%). Two thirds of patients seen were female with a higher percentage of female patients in the non type-I hypersensitivity group (71%) than the type 1 hypersensitivity (66%) (χ2 = 5.1, 1df, p = 0.024). The type 1 hypersensitivity patients were younger than other patients (38 Vs 46 years, t = -10.8, p < 0.001)

This study highlights the complexity of specialist allergy practice and the large proportion of patients referred with non-type I hypersensitivities, chronic idiopathic (spontaneous) urticaria being by far the largest group. Such information is critical to inform commissioning decisions, define referral pathways and in primary care education.