Sublingual immunotherapy persistence and adherence in real-world settings: A systematic review

Sublingual immunotherapy (SLIT) adherence in the literature is often evaluated in closely monitored trials that may impact patient behavior; real-world SLIT adherence is relatively unknown. This systematic review intends to assess SLIT adherence in studies that reflect real-world settings.

A literature search of PubMed, Embase, Cochrane, Web of Science, and Scopus for real-world studies examining SLIT adherence was performed. Monitored clinical trials were excluded. Paired investigators independently reviewed all articles. For this review, "persistence" was defined as continuing therapy and not being lost to follow-up and "adherence" as persistence in accordance with prescribed SLIT dose, dosing schedule, and duration. Article quality was assessed using a modified Newcastle-Ottawa scale and then converted to AHRQ standards (good, fair, and poor).

The search yielded 1596 nonduplicate abstracts, from which 32 articles (n = 63,683 patients) met criteria. Twenty-six (81%) studies reported persistence rates ranging from 7.0% to 88.7%, and 18 (56%) reported adherence rates ranging from 9.6% to 97.0%. Twenty-one (66%) studies surveyed reasons for discontinuing SLIT. All studies were Oxford level of evidence 2b and of good (n = 12) to fair (n = 20) quality.

Reported rates of real-world SLIT persistence and adherence varied widely by study methodology (e.g., follow-up duration, objective vs. subjective assessment). Studies with longer follow-up generally reported lower rates; 3-year persistence ranged from 7% to 59.0% and 3-year adherence from 9.6% to 49.0%. Future studies of SLIT adherence would benefit from following concordant definitions of persistence/adherence and standardized reporting metrics.