Delirium is characterized by the rapid onset of symptoms which fluctuate, with an altered level of consciousness, global disturbance of cognition, perceptual abnormalities and evidence of a physical cause (DSM-IV-R, 2002).

To review the characteristics and psychometric properties of thirteen Delirium scales available in research and clinical practice.

MEDLINE database was used to identify the delirium scales in use (1990–2010), using the keywords: delirium, confusion, questionnaires, scales, severity and screening. Only validation studies were included. Exclusion criteria were children and alcohol/drug delirium assessment scales. This study included seven screening scales: Confusion Assessment Method, Intensive Care Delirium Screening Checklist, Delirium Symptom Interview, NEECHAM Confusion Scale, Cognitive Test for Delirium, Delirium Observation Screening, Nursing Delirium Screening Scale and seven severity scales: Delirium Rating Scale, Memorial Delirium Assessment Scale, Confusional State Evaluation, Delirium Severity Scale, Delirium Index and Delirium-O-Meter.

The majority of scales were based on the Diagnosis Statistical Manual Criteria as well as on a review of selected symptoms of Delirium informed by systematic clinical observation and formal brief assessment of mental status. In most of the studies, for psychometric analysis, the inter-rater reliability and validity with severity of Delirium assessment and cognitive screening tests were used.

Bearing in mind the recent review studies included, we can conclude that CAM is the most widely used instrument for delirium assessment.