BACKGROUND: Adherence is essential for the long-term efficacy of allergen immunotherapy (AIT) and has been evaluated in numerous retrospective studies. However, there are no published guidelines for best practice in measuring and reporting adherence or persistence to AIT, which has resulted in substantial heterogeneity among existing studies. The 'adherence and persistence in AIT (APAIT)' checklist has been developed to guide the reporting, design and interpretation of retrospective studies that evaluate adherence or persistence to AIT in clinical practice.

METHODS: Five existing checklists, focussing on study protocol design, the use of retrospective databases/patient registries, and the appraisal and reporting of observational studies, were identified and merged. Relevant items were selected and tailored to be specific to AIT. The content of the checklist was discussed by 11 experts from Europe, the United States and Canada, representing allergy, healthcare and life sciences, and health technology appraisal.

RESULTS: The APAIT checklist presents a set of items that should either be included or at least considered, when reporting retrospective studies that assess adherence or persistence to AIT. Items are organized into four categories comprising study objective, design and methods, data analysis, and results and discussion. The checklist highlights the need for clarity and transparency in reporting and emphasizes the importance of considering potential sources of bias in retrospective studies evaluating adherence or persistence to AIT.

CONCLUSIONS: The APAIT checklist provides a pragmatic guide for reporting retrospective adherence and persistence studies in AIT. Importantly, it identifies potential sources of bias and discusses how these influence outcomes.