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New tool determines risk for cognitive decline

A new tool, QuoCo, showed diagnostic accuracy and validity in tracking cognitive performance in adults as indicated by Mini-Mental State Examination measurements, according to findings recently published in the Canadian Medical Association Journal.

“It remains unclear how to interpret changes in [the Mini-Mental State Examination] score over time to distinguish age-associated cognitive decline from an early degenerative process,” Patrick J. Bernier, MD, PhD, of the Services Gériatriques Spécialisés in Quebec, Canada, and colleagues wrote. “We aimed to generate ready-to-use cognitive charts for follow-up of age-associated cognitive decline, analogous to pediatric growth charts, based on key predictors of incipient decline in the Mini-Mental State Examination, to allow simple clinical follow-up of age-associated cognitive decline by first-line physicians using the Mini-Mental State Examination.”

Researchers gathered data from 7,569 participants aged older than 65 years from the Canadian Study of Health and Aging who took a Mini-Mental State Examination at baseline, 5 years and 10 years. Researchers constructed a model to foretell these test scores in healthy controls. This model was then converted into simplified linear form to create the cognitive charts.

Bernier and colleagues then searched for the “optimal cognitive decline rate” to distinguish between participants with dementia (n = 1,158) and healthy controls (n = 6,411) The model’s validity was ascertained using an outside cohort of 6,501 participants in the National Alzheimer’s Coordinating Center’s Uniform Data Set, according to researchers.

Researchers wrote that at baseline, the cognitive charts had a specificity of 89% (95% CI, 88-90) and a sensitivity of 80% (95% CI, 75-84) for distinguishing healthy controls vs. those with dementia. Nearly identical specificities and sensitivities were seen for a decline over time greater than 1 percentile zone from the first measurement. The validation sample had comparable results, although it had lower sensitivities. The negative predictive value was 99%.

“QuoCo proved equal to a cut-off approach, while offering numerous critical advantages over and beyond cut-off scores: longitudinal tracking of performance along an outstanding data set; better assessment of high initial Mini-Mental State Examination scores; less vulnerability to ceiling and floor effects; visually combining age and education on the same graph; less statistical variation in sensitivity and specificity over time and population subgroups (age, gender, education); and a visual representation of the concept of cognitive reserve,” researchers wrote.

The tool mirrors the pediatric growth charts, researchers wrote, and “implies an ability to prompt earlier investigation for an adult who ‘fell off’ the curve.” They added patients whose charts show decline should undergo “further detailed investigation”.

In a related commentary, Andrew Costa, PhD, of the department of medicine at McMaster University in Hamilton, Ontario, Canada, pointed out QuoCo’s potential limitation.

“The authors conclude that cognitive charts are possible for other brief cognitive screening tests to maximize interpretation in practice,” he wrote. “However, the widespread benefits derived from cognitive charts for any screening examination rests on the assumption that at-risk patients are being screened systematically over time and that results from cognitive tests are communicated to, or can be readily referenced by, physicians.” – by Janel Miller

For more information: www.quoco.org

Disclosures: Bernier reports patent 62/403,984 pending. None of the other authors report any relevant financial disclosures.