Sublingual immunotherapy in youngsters: Adherence in a randomized clinical trial

Background: Adherence is essential for effective treatment. Although several trials on the efficacy of sublingual immunotherapy (SLIT) in youngsters have been published, few contain data on medication intake. Objective: We aimed to quantify adherence both to study protocol and medication intake as well as to identify factors that may influence adherence to SLIT in youngsters with rhinoconjunctivitis. Methods: Two hundred and four youngsters (6-18 years) with hayfever participated in a randomized controlled trial and used grass pollen extract or placebo for 2 years. The primary outcome of the trial was the mean daily total rhinoconjunctivitis symptom score in the second grass pollen season. Participants having completed the follow-up were considered adherent to the study protocol. Adherence to medication intake was assessed by weighing the study medication. Participants who completed the follow-up and used ≥80% of the prescribed medication were considered adherent to medication intake. Patient-, disease- and treatment-related factors were analysed. Results: One hundred and fifty-four youngsters completed the study. The main reason for discontinuation was the inability to take medication according to schedule. Drop-outs were older, had more difficulty following the medication instructions and their overall evaluation of the treatment effect was lower. The number and reasons for drop-out did not differ between treatment groups. In total, 77% of the participants was adherent to medication intake. Self-reported adherence was 99%. Non-adherent participants experienced more severe symptoms before the trial. Symptom scores did not differ between adherent and non-adherent participants. In adherent as well as non-adherent participants, no difference was found between verum and placebo group with respect to symptom scores. Conclusion: Adherence to both study protocol and medication intake was good. Drop-out was affected by age, evaluation of the treatment effect and medication instructions. Non-adherence to medication intake was influenced by the severity of the disease before the trial. The ineffectiveness of SLIT could not be explained by non-adherence.

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