To assess the validity and the reliability of the Portuguese version of the Delirium Rating Scale-Revised-98 (DRS-R-98).
The scale was translated into Portuguese and back-translated into English. After assessing its face validity, five diagnostic groups (n=64; delirium, depression, dementia, schizophrenia and others) were evaluated by two independent researchers blinded to the diagnosis. Diagnosis and severity of delirium as measured by the DRS-R-98 were compared to clinical diagnosis, Mini-Mental State Exam, Confusion Assessment Method, and Clinical Global Impressions scale (CGI).
Mean and median DRS-R-98 total scores significantly distinguished delirium from the other groups (p<0.001). Inter-rater reliability (ICC between 0.9 and 1) and internal consistency (alpha=0.91) were very high. DRS-R-98 severity scores correlated highly with the CGI. Mean DRS-R-98 severity scores during delirium differed significantly (p<0.01) from the post-treatment values. The area under the curve established by ROC analysis was 0.99 and using the cut-off value of 20 the scale showed sensitivity and specificity of 92.6% and 94.6%, respectively.
The Portuguese version of the DRS-R-98 is a valid and reliable measure of delirium that distinguishes delirium from other disorders and is sensitive to change in delirium severity, which may be of great value for longitudinal studies.