Attention! A good bedside test for delirium?

Abstract

Background: Routine delirium screening could improve delirium detection, but it remains unclear as to which screening tool is most suitable. We tested the diagnostic accuracy of the following screening methods (either individually or in combination) in the detection of delirium: MOTYB (months of the year backwards); SSF (Spatial Span Forwards); evidence of subjective or objective 'confusion'.

Methods: We performed a cross-sectional study of general hospital adult inpatients in a large tertiary referral hospital. Screening tests were performed by junior medical trainees. Subsequently, two independent formal delirium assessments were performed: first, the Confusion Assessment Method (CAM) followed by the Delirium Rating Scale-Revised 98 (DRS-R98). DSM-IV (Diagnostic and Statistical Manual of Mental Disorders, fourth edition) criteria were used to assign delirium diagnosis. Sensitivity and specificity ratios with 95% CIs were calculated for each screening method.

Results: 265 patients were included. The most precise screening method overall was achieved by simultaneously performing MOTYB and assessing for subjective/objective confusion (sensitivity 93.8%, 95% CI 82.8 to 98.6; specificity 84.7%, 95% CI 79.2 to 89.2). In older patients, MOTYB alone was most accurate, whereas in younger patients, a simultaneous combination of SSF (cut-off 4) with either MOTYB or assessment of subjective/objective confusion was best. In every case, addition of the CAM as a second-line screening step to improve specificity resulted in considerable loss in sensitivity.

Conclusions: Our results suggest that simple attention tests may be useful in delirium screening. MOTYB used alone was the most accurate screening test in older people.

Keywords: ATTENTION; COGNITION; NEUROPSYCHIATRY.

Figure 1

Testing processes using different test combination models a) Example of simultaneous testing (a): Two screening tests administered simultaneously. Further assessment required if either test failed. b) Example of simultaneous testing (b): Two screening tests administered simultaneously. Further assessment required only if both tests failed c) Example of sequential testing: First screening test is performed. Proceed to second screening test only if first test failed. Then proceed to further assessment only if second test is also failed. (MOTYB=months of the year backwards test; SSF5=spatial span forwards test with a cutoff of 5).

Figure 2

Flow of patients through the study.

Figure 3

Forest plots depicting performance of tests individually and in combination: sensitivity and specificity plotted with 95% confidence intervals 3a) Sensitivity of each individual test, with and without the CAM as a second–line test 3b) Specificity of each individual test, with and without the CAM as a second–line test 3c) Most efficient test combinations, sensitivity 3d) Most efficient test combinations, specificity (MOTYB=Months of the year backwards; SSF5=SSF with cutoff of 5; SSF4= SSF with cutoff of 4; Pt pos=Subjective confusion (patient felt subjectively confused when questioned); Nurse pos=nurse thought patient was confused when questioned; Med pos=‘confusion’ or proxy term documented in the patient's medical notes; Nurse or med pos=Objective confusion (either nurse felt patient was confused or ‘confusion’ or proxy term was documented in the medical notes); Nurse/med pos=objective confusion (by nurse report and/or medical documentation); CONF/MOTYB pos=any evidence of confusion and/or MOTYB failed; CONF/SSF5 pos=any evidence of confusion and/or SSF failed with a cutoff of 5; CONF/SSF4 pos=Any evidence of confusion and/or SSF failed with a cutoff of 4; MOTYB/SSF5 pos=MOTYB failed and/or SSF5 failed with a cutoff of 5; MOTYB/SSF4 pos=MOTYB failed and/or SSF failed with a cutoff of 4]

Figure 3

Forest plots depicting performance of tests individually and in combination: sensitivity and specificity plotted with 95% confidence intervals 3a) Sensitivity of each individual test, with and without the CAM as a second–line test 3b) Specificity of each individual test, with and without the CAM as a second–line test 3c) Most efficient test combinations, sensitivity 3d) Most efficient test combinations, specificity (MOTYB=Months of the year backwards; SSF5=SSF with cutoff of 5; SSF4= SSF with cutoff of 4; Pt pos=Subjective confusion (patient felt subjectively confused when questioned); Nurse pos=nurse thought patient was confused when questioned; Med pos=‘confusion’ or proxy term documented in the patient's medical notes; Nurse or med pos=Objective confusion (either nurse felt patient was confused or ‘confusion’ or proxy term was documented in the medical notes); Nurse/med pos=objective confusion (by nurse report and/or medical documentation); CONF/MOTYB pos=any evidence of confusion and/or MOTYB failed; CONF/SSF5 pos=any evidence of confusion and/or SSF failed with a cutoff of 5; CONF/SSF4 pos=Any evidence of confusion and/or SSF failed with a cutoff of 4; MOTYB/SSF5 pos=MOTYB failed and/or SSF5 failed with a cutoff of 5; MOTYB/SSF4 pos=MOTYB failed and/or SSF failed with a cutoff of 4]

Figure 4

A suggested approach to delirium screening in the acute hospital setting (MOTYB;months of the year backwards test; SSF4;spatial span forwards test with a cutoff of 4).