Indications for house dust mite allergen–specific immunotherapy

• Published in: Hong Kong medical journal = Xianggang yi xue za zhi Vol. 29; no. 5; pp. 469 - 471
• Main Authors: Leung, Christy WM, Chu, H C, Leung, Jonathan CH, Leung, T F
• Format: Journal Article
• Language: English
• Published: Hong Kong Hong Kong Academy of Medicine 01.10.2023
• Subjects: Allergens; Anaphylaxis; Asthma; Cost analysis; Dermatitis; Disease; Food allergies; Hay fever; Immunotherapy; Patients; Pediatrics; Rhinitis; Hong Kong China; China
• ISSN: 1024-2708; 2226-8707
• DOI: 10.12809/hkmj2310696

Characteristics of allergen-specific immunotherapy Allergen-specific immunotherapy (AIT), which is yet to be popularised in Hong Kong, is a disease-modifying therapy.3 It modifies the host immune system to the state of immunological tolerance by reducing mast cell activity and IgE release in response to allergen exposure, while also increasing numbers of regulatory T-cells.3 House dust mite allergen[-]specific immunotherapy There are various AIT formulations, including those that target HDM allergens.4 The initiation of HDM AIT requires that allergic disease be diagnosed by a physician and that sensitisation be demonstrated by measurement of serum HDM-specific IgE levels or a positive skin prick test to extracts from D pteronyssinus and D farinae. Disease factors Severity Clinical confirmation of allergic disease and atopy-triggered disease burden are equally important for assessing severity, with the latter categorised using established grading systems, including the ARIA (Allergic Rhinitis and its Impact on Asthma) guideline,9 the Asthma Control Test,10 and the Scoring Atopic Dermatitis (SCORAD) index.11Both the ARIA guideline and the Asthma Control Test assess the effects of allergic disease and atopic symptoms on quality of life and activities of daily living; at the same time, they inquire about sleep disturbances and use of rescue medication, respectively.9 10 On the other hand, the SCORAD index includes both subjective assessment of pruritus and sleep disturbance as well as objective signs of typical cutaneous manifestations.11 Contra-indications Concomitant use of beta-blockers and poorly controlled asthma are well-established and absolute contra-indications to AIT,12 since these patients are at risk of more severe AEs and treatment-resistant anaphylaxis.7 12 In fact, the majority of AIT-associated deaths have occurred in severe asthmatics.13 Relative contra-indications include coexisting active autoimmune disease and active malignancies,14since there is an argument for the use of a risk-benefit analysis in such patients. While it is a self-financed item and mainly administered as a private healthcare service in Hong Kong,15 the cost is covered by health insurance in some countries.16 The availability of insurance coverage and ease of making claims are significant factors in patients continuing treatment.16 Cost-effectiveness Although the costs of AIT are not available for public reference, several studies have assessed its incremental cost-effectiveness ratio.7 Healthcare authorities in countries across the world set their own cost-effectiveness thresholds, albeit with varying values, and treatments with sub-threshold incremental cost-effectiveness ratios are considered to be cost-effective. [...]contrary to the popular belief that AIT takes years to work, clinical improvements can be observed at as early as 8 weeks for ocular symptoms (any watery, red, gritty or itchy eyes) and 14 weeks for nasal and asthmatic symptoms.8 18 The onset of action varies according to treatment dose and the type and severity of allergic disease.8 Allergen-specific immunotherapy, which is currently the only curative therapy for allergy, is associated with long-term symptom remission.19 In a study by Cools et al,19 patients with asthma either received the standard level of care or HDM AIT.