Academic journal article South African Journal of Psychiatry

Sensitivity and Specificity of Neuropsychological Tests for Dementia and Mild Cognitive Impairment in a Sample of Residential Elderly in South Africa

Academic journal article South African Journal of Psychiatry

Sensitivity and Specificity of Neuropsychological Tests for Dementia and Mild Cognitive Impairment in a Sample of Residential Elderly in South Africa

Article excerpt

A growing number of people are surviving into old age, with an associated increase in the prevalence of dementia. [1] It has been postulated that up to 80% of cases remain undiagnosed, [2] which has resulted in a call for dementia to be regarded as a global health priority. [3] The accurate detection of cognitive deficits due to dementia and mild cognitive impairment (MCI), a predementia stage, is important to distinguish these from normal age-associated cognitive deficits. Delaying the progression from MCI to dementia by even 1 year has been shown to result in significant cost savings. [4]

The absence of reliable, universally acceptable biological and radiological markers for dementia necessitates the reliance on clinical assessments for a diagnosis, [5] supported by the assessment of cognitive disturbances using a range of screening tests. The use of neuropsychological screening tests allows for the assessment of specific cognitive domains, can distinguish age-related cognitive deficits from those due to MCI or dementia, and is superior to brief cognitive tools for which floor and ceiling effects threaten their validity. [6,7] There is currently no universally accepted battery of tests for MCI[8,9] and the functioning of neuropsychological tests in low-resource residential settings in South Africa (SA) has not been widely tested.

The objective of this study was to determine the sensitivity and specificity of a battery of neuropsychological tests in a sample of elderly persons living in a residential setting in SA.

Methods

The research was conducted from 2010 to 2011 on residents aged [greater than or equal to] 60 years (N=1 371) in a group of residential homes in Durban, KwaZulu-Natal Province, SA. The homes are administered by a nongovernmental organisation and cater for those needing frail care, assisted living and independent living. Inclusion criteria for the study were: randomly selected residents [greater than or equal to] 60 years; with a minimum of 8 years of formal schooling; the ability to speak, read and write in English; and the ability to give written, informed consent. Exclusion criteria were severe physical, mental or sensory handicaps that precluded engagement in the assessment procedures. The study comprised three stages of cognitive assessments, conducted sequentially. In stage 1, a random sample (n=302) of residents aged [greater than or equal to] 60 years was selected based on a statistical calculation from all the homes. The Mini-Mental State Examination (MMSE), [10] a subjective memory rating scale, [11] and an informant questionnaire, the Deterioration Cognitive Observee (DECO), [12] were used to screen for dementia. [13] The sample size was calculated on a sensitivity and specificity of 85% for the MMSE[14] and a conservative estimate of 20% prevalence for dementia in residential homes, based on the reported ranges of 16[15]-75%. [16] In stage 2, 140 participants from stage one, including MMSE screen positives and a random selection of MMSE screen negatives, were clinically assessed by psychiatrists and categorised as having dementia, MCI or not being clinically cognitively impaired. [17] Diagnostic and Statistical Manual of Mental Disorders, 4th edition (text revised) criteria A and B for Alzheimer's and vascular dementia were used to assign a general diagnosis of dementia without reference to aetiology. [18] MCI was diagnosed using the criteria contained in the report of the International Working Group on mild cognitive impairment. [19] In stage 3, the 140 participants from stage 2 were available and consented to the administration of a neuropsychological battery of tests. Of these, 2 participants died during the study and 20 either refused or were unavailable to participate. One person was unable to complete any of the neuropsychological tests and was excluded from the dataset. Of the remaining 117 participants, 9 were participants with a diagnosis of dementia, 30 with MCI and 78 participants did not meet diagnostic criteria and were classified as controls. …

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