Development of a smartphone application for the objective detection of attentional deficits in delirium

Background: Delirium is an acute, severe deterioration in mental functioning. Inattention is the core feature, yet there are few objective methods for assessing attentional deficits in delirium. We previously developed a novel, graded test for objectively detecting inattention in delirium, implemented on a computerized device (Edinburgh Delirium Test Box (EDTB)). Although the EDTB is effective, tests on universally available devices have potential for greater impact. Here we assessed feasibility and validity of the DelApp, a smartphone application based on the EDTB. Methods: This was a preliminary case-control study in hospital inpatients (aged 60-96 years) with delirium (N = 50), dementia (N = 52), or no cognitive impairment (N = 54) who performed the DelApp assessment, which comprises an arousal assessment followed by counting of lights presented serially. Delirium was assessed using the Confusion Assessment Method and Delirium Rating Scale-Revised-98 (DRS-R98), and cognition with conventional tests of attention (e.g. digit span) and the short Orientation-Memory-Concentration Test (OMCT). Results: DelApp scores (maximum score = 10) were lower in delirium (scores (median(IQR)): 6 (4-7)) compared to dementia (10 (9-10)) and control groups (10 (10-10), p-values < 0.001). Receiver operating characteristic (ROC) analyses revealed excellent accuracy of the DelApp for discriminating delirium from dementia (AUC = 0.93), and delirium from controls (AUC = 0.99, p-values < 0.001). DelApp and DRS-R98 severity scores were moderately well correlated (Kendall's tau = -0.60, p < 0.001). OMCT scores did not differ between delirium and dementia. Conclusions: The DelApp test showed good performance, supporting the utility of objectively measuring attention in delirium assessment. This study provides evidence of the feasibility of using a smartphone test for attentional assessment in hospital inpatients with possible delirium, with potential applications in research and clinical practice.