Over the years many scales have been designed for screening, diagnosis and 
assessing the severity of delirium. In this paper we review the various 
instruments available to screen the patients for delirium, instruments available 
to diagnose delirium, assess the severity, cognitive functions, motoric 
subtypes, etiology and associated distress. Among the various screening 
instruments, NEECHAM confusion scale and delirium observation scale appear to be 
most suitable screening instrument for patients' in general medical and surgical 
wards, depending on the type of rater (physician or nurse). In general, the 
instruments which are used for diagnosis [i.e., confusion assessment method 
(CAM), CAM for intensive care unit (CAM-ICU), Delirium Rating Scale-revised 
version (DRS-R-98), memorial selirium assessment scale, etc.] are based on 
various Diagnostic and Statistical Manual criteria and have good to excellent 
reliability and fair to good validity. Among the various diagnostic instruments, 
CAM is considered to be most useful instrument because of its accuracy, brevity, 
and ease of use by clinicians and lay interviewers. In contrast, DRS-R-98 
appears to be a comprehensive instrument useful for diagnosis, severity rating 
and is sensitive to change and hence can be used for monitoring patients over a 
period. In the ICU setting, evidence suggests that CAM-ICU and Nursing Delirium 
Screening Scale had comparable sensitivities, but CAM-ICU has higher 
specificity. With regard to assessment of delirium in pediatric age group, 
certain instruments like Pediatric Anesthesia Emergence Delirium scale and 
pediatric CAM-ICU has been designed and have been found to be useful.