Inter-rater reliability of delirium rating scales

Delirium continues to be under-recognized despite use of rating scales with apparently high inter-rater reliability. We analyzed the inter-reliability data of published rating scales for delirium using a standard questionnaire to evaluate if the inter-rater reliability was assessed rigorously. Most studies employed a heterogeneous group of cognitively disordered elderly, however other aspects of inter-rater reliability estimation were less than rigorous. This suggests that the reported reliability may be spuriously high, which may have implications on the ability of clinicians to discriminate delirium from other causes of cognitive impairment in practice. The methodology of assessing inter-rater reliability of delirium scales needs to improve and reliability should be evaluated when the settings of administration change substantially.