May 14, 2018
Adding the Visual Association Test (VAT) to the Mini-Mental State Examination (MMSE) increases its accuracy in predicting dementia, researchers say.
"Our findings show that the VAT score has incremental value in discriminating between older adults with and without increased risk of dementia, especially among those with a (minor) decline in MMSE score," Susan Jongstra, MD, PhD, from the University of Amsterdam, the Netherlands, and colleagues write. They published their findings online May 14 in the Annals of Family Medicine.
Screening for dementia can help clinicians tailor their treatments and patients and caregivers plan for their needs. Many clinicians use the MMSE for this purpose, but its sensitivity for early stages of cognitive impairment is limited.
Jongstra and colleagues reasoned that the VAT might supplement the MMSE, as it only takes 3 minutes to administer and has good characteristics for the detection of early signs of Alzheimer's disease. It has a higher specificity and positive predictive value for dementia than other cued recall tasks, they write.
The researchers drew a study sample from the Prevention of Dementia by Intensive Vascular Care (preDIVA) trial, which assessed the efficacy of intensive vascular care on the prevention of dementia in a primary care population of 3526 older adults 70 to 78 years old.
The patients did not have dementia or MMSE scores of 24 or lower. As the vascular care did not affect the incidence of dementia, the investigators analyzed the whole population as a single cohort. They excluded patients diagnosed with dementia within 2 years and 3 months, as they were only interested in predicting long-term diagnoses.
Administration of the MMSE takes between 5 and 10 minutes and examines functions including registration (repeating named prompts), attention and calculation, recall, language, ability to follow simple commands, and orientation. It has a maximum score of 30 points, with higher scores indicating more normal cognition.
The VAT consists of six "cue" cards showing an image of an object and six "target" cards showing the same image with a second, unexpected object added. Patients identify the object in the cue card (eg, an ape) and then the two objects in the target card (eg, an ape holding an umbrella). Finally, patients see the cue card a second time and are asked what is different (in this example, the umbrella). The maximum score is 6 points, with 1 point added for each correctly recalled target.
The researchers measured change over time by comparing scores on the two tests at baseline with scores after 2 years.
They identified 2648 patients without dementia at baseline who were assessed on both tests at 2 years and were evaluated for dementia after a median follow-up of 6.7 years. Among these patients, 157 received a dementia diagnosis.
Patients with a 2-year decline in MMSE of 2 or more had a 3.55 (95% confidence interval [CI], 2.51 - 5.00) odds ratio for dementia. Patients with an imperfect VAT score at 2 years had a 3.28 (95% CI, 2.35 - 4.58) odds ratio for dementia.
Patients with both a decline in MMSE and an imperfect VAT had an odds ratio of 9.55 (95% CI, 5.89 - 15.41) of dementia.
Patients with a 2-point decline in MMSE had a 10.1% increased risk for dementia. This rose to 14.4% if the same patient had an imperfect VAT. Those who had a 3-point decline in MMSE had a 20.8% increased risk, which increased to 29.3% with an imperfect VAT.
Although the differences between the MMSE scores alone and the MMSE scores with the VAT were only incremental, they were significant. The percentage of patients who developed dementia with a decline of 1 to 2 points was not statistically different from the baseline risk, but when combined with an imperfect VAT score, this change in MMSE score was significant and clinically meaningful, the researchers write.
"Among older adults with a minor decline on the MMSE, the VAT — a 3-minute easily administered test of associative memory — can help to distinguish those at increased risk of developing dementia (requiring counseling, additional examination, or both) from those in whom watchful waiting is justified," they conclude.
The preDIVA study was funded by the Dutch Ministry of Health, Welfare and Sport; Dutch Innovation Fund of Collaborative Health Insurances; and Netherlands Organisation for Health Research and Development.
Ann Fam Med. Published online May 14, 2018.