Delirium is a common neuropsychiatric syndrome with considerable heterogeneity in clinical profile. Rapid reliable identification of clinical subtypes can allow for more targeted and research efforts.

The aims of this study are to evaluate the concurrent validity (agreement) and reliability (internal consistency) of DMSS-4 in a new cohort of delirious hospitalised patients.

We explored the concordance in attribution of motor subtypes between the DMSS-4 and the original DMSS (assessed cross-sectionally) and subtypes defined longitudinally using the Delirium Symptom Interview (DSI) method.

We included 118 elderly patients developing DSM-IV delirium after hip-surgery [mean age 87.0±6.5 years; range 65–102; 66% females; 28 (23.7%) had no previous history of cognitive impairment]. Concordance was high for both the DMSS-4 and original DMSS (k=0.80), and for the DMSS-4 and DSI methods (k=0.82). The DMSS-4 also demonstrated high internal consistency (McDonald's omega = 0.78). The DMSS-11 and DMSS-4 had higher inclusion for motor subtypes than the DSI method.

The DMSS-4 provides an ultra-rapid means of identifying motor-defined clinical subtypes of delirium and is a reliable alternative to the more detailed and time-consuming original DMSS and DSI methods of subtype attribution. The DMSS-4 can be readily applied to further studies of causation, treatment and outcome in delirium.