The impact of different diagnostic criteria on prevalence rates for delirium

A cross-sectional study was performed to evaluate the concordance of the present criteria of delirium among elderly (>70 years) geriatric hospital patients (n = 230) and nursing home residents (n = 195). Different subjects were diagnosed as having delirium when operationalized criteria according to the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders (DSM-III, DSM-III-R, DSM-IV) and the World Health Organization's International Classification of Diseases (ICD-10) were used. Whereas 132 subjects (31.1%) met the criteria for delirium by at least 1 classification, only 25 (5.9%) met all 4. The most inclusive was the DSM-IV (24.9% of the subjects) followed by DSM-III-R (19.5%), DSM-III (18.8%) and ICD-10 (10.1%), respectively. The DSM-IV and ICD-10 had the largest number of patients not overlapping with any other diagnostic group. The newest DSM-IV classification found more cases of delirium especially among acutely ill, hospitalized patients.