When expert agreement replaces evidence: The rise of Delphi consensus in geriatrics.

Expert consensus is intended to guide clinical reasoning when evidence is scarce. In contemporary geriatrics, however, the Delphi method is increasingly used where data are not absent but abundant. Sarcopenia and frailty exemplify this dilemma. Repeated consensus statements have redefined diagnostic criteria and thresholds, yet prevalence estimates range dramatically depending on the framework applied. The proliferation of overlapping definitions and tools has generated conceptual instability, fragmented research efforts, and hindered therapeutic development. When expert agreement becomes the endpoint rather than a bridge to empirical confirmation, consensus risks hardening into doctrine. Geriatrics stand at a methodological crossroads. A discipline that cares for more than 830 million older adults cannot rely on authority in place of evidence. Consensus methods retain value in genuine uncertainty, but their output must be explicitly provisional and rapidly subjected to validation against meaningful clinical outcomes. Without recalibrating the balance between expertise and data, geriatrics risk weakening its scientific credibility at precisely the moment when demographic change demands greater rigor. Evidence, not agreement, must define the future of the field.