WASHINGTON, DC—The role of screening instruments and neuropsychologic tests in the evaluation of patients with mild cognitive impairment (MCI) and Alzheimer’s disease was discussed by leading researchers at the 2008 Alzheimer’s Disease Summit. Each test has its advantages and disadvantages, according to the investigators, who provided insight regarding when each should be used in clinical practice.
Ziad Nasreddine, MD, Assistant Clinical Professor at Université de Sherbrooke and McGill University in Montreal, reviewed the strengths and weaknesses of commonly used dementia screening tests. These include the 7-Minute Screen, Mini-Cog, Mini-Mental State Examination (MMSE), Memory Impairment Screen, Short Test of Mental Status, Abbreviated Mental Test, 6-Item Screener, Hopkins Verbal Learning Test, 6-Item Cognitive Impairment Test, and Clock Drawing Test. Two new screening tests are the DemTect and the Montreal Cognitive Assessment (MoCA), the latter of which was developed by Dr. Nasreddine.
Physicians should consider the sensitivity and specificity for Alzheimer’s disease or MCI and time required for administration when choosing which screening test to use, advised Dr. Nasreddine. For example, the MMSE is sensitive for moderate-stage dementia but may not detect MCI, and it takes about eight minutes to perform. The Mini-Cog, which can be completed in three minutes, has good sensitivity for moderate Alzheimer’s disease but low sensitivity for MCI and is recommended for use by primary care physicians, he noted. Conversely, he added, the MoCA has excellent sensitivity for both Alzheimer’s disease and MCI, but it takes about 10 minutes to complete.
Dr. Nasreddine outlined screening algorithms for suspected dementia or MCI. To screen for Alzheimer’s disease, he recommended that physicians begin with short screening tests, such as the Mini-Cog or MMSE. If results are positive, then the patient needs further investigation; if results are negative, longer screening tests can be used to try to detect Alzheimer’s disease. When screening for MCI, physicians should begin with longer screening tests such as the DemTect or MoCA, according to Dr. Nasreddine. If findings are negative, the patient can be reassured; if they are positive, then further investigation and follow-up of the patient are warranted.
Neuropsychologic Testing
Neuropsychologic testing can help differentiate neurodegenerative disorders, such as Alzheimer’s disease, from frontotemporal dementia, as well as sort out the impact of medical and psychiatric comorbidities on cognitive function, said Kathleen Welsh-Bohmer, PhD, Director of the Bryan Alzheimer’s Disease Research Center at Duke University Medical Center, Durham, North Carolina. According to Dr. Welsh-Bohmer, neuropsychologic testing can also help track cognitive effects over time and monitor the effects of treatment. For the clinician, neuropsychologic testing may be useful to determine functional capacities and competency, which may aid patient management. For example, testing can be used to evaluate a patient’s ability to live independently, manage his or her finances and medication, provide testamentary capacity, treatment consent, sexual consent, and research consent, drive safely, and vote. Test results can help guide compensatory strategies, psychotherapy, and behavior management.
Computerized Testing
Several computerized neuropsychologic testing batteries are also available, such as Mindstreams, Cambridge Cognitive Examination, Cambridge Neuropsychological Test Automated Battery, and experimental laboratory software. Ellen Woo, PhD, a postdoctoral fellow in neuropsychology at the University of California at Los Angeles, discussed the advantages and disadvantages of computerized neuropsychologic testing in the assessment of older adults.
“Computerized tests can give objective data and provide information for referral to a neuropsychologist,” said Dr. Woo. Advantages of computerized testing include shorter assessment time (often less than one hour), adapted presentation of items to prevent floor and ceiling effects, precise measurement at the millisecond level, automatic scoring (which decreases human scoring error), easy portability, and fewer examiner effects. Older patients may find that computerized tests are not stressful or difficult to complete.
Disadvantages of computerized neuropsychologic testing include the need for adequate visual and auditory acuity, which may be problematic in elderly patients. In addition, multiple-choice responses, which are typically elicited in computerized tasks, provide less qualitative information than patient-generated responses and include an element of chance. Because of these and other limitations, clinicians should not make a diagnosis of Alzheimer’s disease based on only one computerized test, advised Dr. Woo.
—Andrew N. Wilner, MD