Delphi Consensus in Otolaryngology: A Systematic Review of Reliability and Reporting Completeness

Background: The Delphi method is increasingly used in otolaryngology to develop consensus in subjects lacking robust evidence. In these contexts, consensus documents play a dual role: they provide structured expert guidance while determining shared principles adaptable to the individual patient. Nevertheless, the methodological rigor and reporting consistency of Delphi studies remain variable, raising concerns about transparency, reproducibility, and potential bias. Methods: A systematic review was conducted according to PRISMA guidelines. MEDLINE, Embase, and Web of Science were searched for Delphi-based consensus studies in otolaryngology. Fully published studies in English, Italian, German, French, or Spanish were included. Each article was assessed using established methodological frameworks for consensus development, bias domains described in the methodological literature, and the DELPHISTAR reporting checklist. Reliability and completeness scores were calculated to enable comparisons. Results: Out of 3168 unique records, 86 studies were included. Most defined their purpose and consensus criteria, but transparency regarding panel selection, anonymity, feedback, and criteria for stopping the consensus process was often missing. Based on methodological bias domains, only 9 studies (10.5%) reached a "good" reliability score, while the majority were rated as "fair." According to DELPHISTAR, just 3 studies (3.5%) showed good levels of completeness. Reporting completeness and risk of bias proved heterogeneous across subspecialties. Conclusions: Delphi-based studies are increasingly shaping clinical practice in otolaryngology, but persistent methodological and reporting limitations undermine their reliability. Wider adoption of standardized frameworks is essential to improve transparency, reproducibility, and clinical impact, ensuring that consensus statements support both evidence-informed practice and personalized patient care.