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SCIT vs SLIT
By Anna Butrymowicz, MD
Allergy Immunotherapy (AIT) is an option for patients with allergic rhinitis (AR), allergic asthma and atopic dermatitis. In the United States, AIT is offered in two forms, subcutaneous immunotherapy (SCIT) and sublingual immunotherapy (SLIT) via tablet or drop. The choice to pursue AIT is one that should be made after thorough discussion with your Otolaryngologist and is normally considered in patients with the above diagnoses who have failed to improve with medical management or cannot tolerate medical management, and avoidance of known allergens is not possible. When deciding between form of AIT (SLIT vs SCIT), a number of things should be considered, including efficacy, cost, compliance, and safety.
Efficacy: the jury is still out. While large Cochrane reviews suggest superiority of SCIT, there are only a few randomized control trials, and these head to head analyses show equivalent benefit in regard to symptom control and medication use (with exception of 1 RTC which shows superiority of SCIT).
Cost: This question is addressed directly in the article Hidden Costs of AIT. Overall, aqueous SLIT is considered off label by the FDA and incurs out of pocket costs. The direct cost of SLIT tablets or co-pays for SCIT depend on insurance coverage. There is also indirect cost to parking, travel time, missed work/school when pursuing SCIT.
Compliance: It seems reasonable to assume that patients would be more compliant with medication they could administer at home, like SLIT, but studies show conflicting evidence, some with higher compliance with SCIT, other with higher compliance with SLIT. Like with every other broad characterization, we have to keep individual patient characteristics/goals in mind, and tailor each treatment plan to the patient.
Safety: SLIT has a superior safety profile, with no history of reported fatalities and a rare incidence of anaphylaxis. In general, SCIT is well tolerated, but there have been reported fatalities and the incidence of anaphylaxis is higher.
Generally, these are the main factors we should consider when discussing AIT with our patients, but this is not a comprehensive list. And while SCIT and SLIT are the forms of AIT offered in the United States, the field of Otolaryngic Allergy continues to innovate, and we may see new options in the future. Stay tuned!