Screening for dementia: single yes/no question or Likert scale?
Dementia is now a major public health issue, but the optimal method of screening for at-risk individuals is unclear. Government directive, from the Dementia Commissioning for Quality and Innovation (Dementia CQUIN),1 advocates a single screening question:Have you been more forgetful in the past 12 months to the extent that it has significantly affected your life?’
In an epilepsy clinic, a population of patients with a high frequency of subjective memory complaints, 48% of patients answered this simple memory screening question in the affirmative, suggesting it would have very low specificity and high probability of identifying false positives.2
Since subjective memory complaints (SMCs) may be associated with subsequent cognitive decline, dementia screening might reasonably be focused on this at-risk population. Screening tests for SMCs are available, such as the five-point Likert scale described by Paradise et al3 in which participants are asked ‘In general, how would you rate your memory?’ with a choice of the following five responses: 1 – poor; 2 – fair; 3 – good; 4 – very good; or, 5 – excellent. The scale defines those rating their memory fair or poor (2 or 1) as experiencing SMCs (SMC+).3 This Likert scale has been used as a screen for SMCs in diagnostic test accuracy studies of cognitive screening instruments for mild cognitive impairment (MCI), which in some instances is a prodromal stage of dementia.4
We administered the SMC Likert scale to 100 consecutive follow-up patients attending a dedicated epilepsy outpatient clinic. Patients were also asked for any examples of their memory problems. Based on Likert scores, groups were categorised as SMC+ (n=20) or SMC– (n=80) and compared (t tests for continuous variables, chi-squared tests for categorical variables; Table 1).
No difference was found in patient age or seizure type (generalised or partial) between SMC+ and SMC– groups. However, there were significant differences in duration of epilepsy and use of antiepileptic drugs (monotherapy versus polytherapy), with longer disease duration and increased frequency of polytherapy in the SMC+ group.
All SMC+ patients commented on memory issues. No SMC– patient with Likert scale scores of 4 or 5 had any memory-related comment, although all SMC– patients with score of 3 did recount examples of memory problems.
This study found a much lower self-rating of memory impairment using the Likert scale than a previous epilepsy clinic-based study that used a single yes/no screening question (20% versus 48%). The single question study found no statistically significant difference in patient age, seizure type, use of anti-epileptic drugs, or duration of epilepsy (trend) between those answering yes or no to the screening question,2 whereas the Likert scale did identify significant differences between epilepsy duration and use of polytherapy between SMC+ and SMC– groups, factors likely to be associated with increasing memory impairment.
Using a Likert scale screening question may provide greater diagnostic discrimination than a simple yes/no question, concordant with evidence that longer cognitive screening instruments have greater diagnostic accuracy.5 Therefore, we suggest that policy on dementia screening might explore this approach.
Conflicts of interest
The authors have no conflicts of interest to declare.
- © Royal College of Physicians 2017. All rights reserved.
References
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- Department of Health
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- Aji BM
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- O’Caoimh R
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- Larner AJ.
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