Diagnosing vascular mild cognitive impairment with atrial Fibrillation remains a challenge.

Ronan O'Caoimh, Junior Doctor,

Other Contributors:

March 05, 2013

To the Editor, we read with interest Ball et al's article exploring the prevalence of mild cognitive impairment (MCI) in patients with chronic atrial fibrillation (AF)[1]. This study suggests that MCI is highly prevalent (50 to 65%), among older, hospitalized patients with AF. This is valuable research, highlighting the much-overlooked association between cognitive impairment (CI) and AF. We feel however, that the prevalence rates reported may over-state the true prevalence of MCI in older adults with AF. In this case, MCI was classified using a cut-off score of less than 26 (or 24) on the Montreal Cognitive Assessment (MoCA), in patients deemed not to have dementia following routine evaluation by hospital clinical teams. While the authors of the article acknowledge that the MoCA is a screening test and that further assessment is required to determine a diagnosis of MCI, using the MoCA as a single cognitive screen presents other challenges that need to be addressed. Firstly, our experience of using the MoCA to identify CI in a memory clinic setting is that it over-estimates CI in older adults with less time in formal education, irrespective of their subtype of CI. Among a sample of patients with memory loss attending our clinic, 50%(30/60) with normal cognition screened positive on the MoCA compared to 13% using a new rapid screen for MCI, the Quick MCI screen (Qmci)[2] and only 3% on the Mini- Mental. Adjusting for age and education, the MoCA misclassified 38.5%(10/26) of those <75 with >12 years education. An acute hospital admission, given the increased likelihood of delirium, is likely to exaggerate this misclassification. Secondly, the diagnosis of MCI itself is under scrutiny given the lack of consensus in developing cut-offs for its defining characteristic, namely the presence of CI without social and functional impairment. Presenting functional data, rather than stating that subjects were living independently, would provide context for the MoCA scores. Furthermore, the diagnostic criteria for MCI related to cerebrovascular disease are even less clearly defined[3], than MCI relating to Alzheimer's dementia. The MoCA has particularly poor specificity in these circumstances, resulting in high false positive rates, which improve after application of age and education adjusted cut-offs[4]. Presenting the prevalence of CI, both MCI and dementia, among similar age and education-matched hospital patients is necessary to give additional context to these results. Defining MCI as a score below a threshold on the MoCA in non-demented persons misses the complexity and can over-estimate the condition. We agree with the authors that cognitive screening is important in persons with AF but reiterate that caution is needed in diagnosing vascular MCI in this fashion.

Conflict of Interest:

None declared

Conflict of Interest

None declared