Carmichael 2007.
| Study characteristics | |||
| Patient sampling |
Primary objectives: to analyse several types of cognitive state transitions—normal to MCI, normal to dementia, MCI to dementia, in an attempt to capture relationships between ventricular structure and highly variable rates of cognitive decline in a population‐based sample (the Pittsburgh Cardiovascular Health Study Cognition Study; Lopez 2003) Study population: participants with MCI Selection criteria: inclusion criteria were designed to capture different forms of cognitive impairment, with or without specific conditions that could themselves cause cognitive deficits. Exclusion criteria: not reported in detail; comorbid conditions were permitted for "possible MCI" (cerebrovascular disease, history of head trauma, encephalopathy, infectious disease, developmental disabilities, systemic illnesses that may cause cognitive deficits) Study design: prospective longitudinal |
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| Patient characteristics and setting |
Clinical presentation: MCI defined as "impairments in delayed recall of verbal material, nonverbal materials, or both; or impairment in at least 1 cognitive domain (other than memory); or 1 abnormal test (which could be a memory test) in at least 2 domains, without severe impairment of IADLs. The cognitive deficits must represent a decline from a previous level of functioning (Lopez 2003). Participants were classified as probable MCI when there were no psychiatric, neurologic (e.g. cerebrovascular disease, history of head trauma encephalopathy, infectious diseases, developmental disabilities), or systemic illnesses that may cause cognitive deficits, or possible when any comorbid condition was present". Age years mean (SD): MCI who progressed to dementia: 84 ± 4 years; stable MCI: 90 ± 5 years; MCI who reverted to normal: 84 Gender (% men): MCI who progressed to dementia: 33%; stable MCI: 56%; reverted to normal: 11% Education (up to/beyond high school): MCI who progressed to dementia: 7/9; stable MCI: 3/9; reverted to normal: 0/1 ApoE4 carriers (%): not stated Neuropsychological tests: modified mean (SD) MCI stable 91.17 ± 5.41, MCI converts 92.44 ± 5.60 Clinical stroke excluded: not specified Co‐morbidities: participants with comorbidities were not excluded Number enrolled: 130 Number available for analysis: 29 (amnestic MCI: 3; multiple cognitive deficit MCI: 26) Setting: University of Pittsburgh Country: USA Period of study: 1997‐2005 Language: English |
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| Index tests |
Index test: MRI automated method for estimation of lateral ventricular and whole‐brain volume Manufacturer: GE Tesla strength: 1.5 Signa scanner with high‐performance gradients Assessment methods: automatic atlas‐based segmentation (Carmichael 2005), for estimation of lateral ventricular volume (validated technique against visual and manual method); whole‐brain mask was output by the skull‐stripping procedure and was used to estimate brain volume in each image Description of positive case definition by index test as reported: criteria for scoring lateral ventricle‐to‐brain ratio volume according to Yue 1997 (normal value in healthy participants reported in the manuscript; cut‐off value for normality not clearly reported; study authors recommended caution against use of the word "abnormal" for grades above the 95th percentile) Examiners: trained neuroradiologists Interobserver variability: not provided |
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| Target condition and reference standard(s) |
Target condition: AD Prevalence of AD in the sample: 12/29 (41% of cases included in the analysis) Stable MCI or converted to other dementia: 17/29 (59%) (12 stable MCI; 1 MCI reverted to normal; 4 MCI converted to other dementia) Reference standard: NINCDS‐ADRDA (McKhann 1984) Mean clinical follow‐up: 3.2 years |
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| Flow and timing |
Withdrawals and losses to follow‐up: 101 (78%) of the 130 enrolled participants excluded for the following: 99 participants excluded because they had not MRI follow‐up, 2 of the remaining 31 participants were excluded and the reason was not reported. Uninterpretable MRI results were not reported |
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| Comparative | |||
| Key conclusions by the authors | Change rate in lateral ventricle‐to‐brain ratio was faster in participants who were had dementia or transitioned from MCI to dementia, compared with participants normal at follow‐up images and participants who transitioned from normal to MCI or dementia | ||
| Conflict of interests | Study authors declared no conflict of interest | ||
| Notes |
Source of funding: National Heart, Lung, and Blood Institute contracts N01‐HC‐85079 through N01‐HC‐85086, N01‐HC‐35129, N01 HC‐15103, N01 HC‐55222, and U01 HL080295; NIH grants NS07391, MH064625, AG05133, DA015900‐01, MH01077, EB001561, RR019771, RR021813, AG016570, AG20098, and AG15928; and additional contribution from the National Institute of Neurological Disorders and Stroke 2 x 2 table: data to complete 2 x 2 table provided by the study authors |
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| Methodological quality | |||
| Item | Authors' judgement | Risk of bias | Applicability concerns |
| DOMAIN 1: Patient Selection | |||
| Was a consecutive or random sample of patients enrolled? | No | ||
| Was a case‐control design avoided? | Yes | ||
| Did the study avoid inappropriate exclusions? | Yes | ||
| High | Low | ||
| DOMAIN 2: Index Test All tests | |||
| Were the index test results interpreted without knowledge of the results of the reference standard? | Unclear | ||
| Did the study provide a clear pre‐specified definition of what was considered to be a "positive" result of the index test? | No | ||
| Was the index test performed by a single operator or interpreted by consensus in a joint session? | Unclear | ||
| High | Low | ||
| DOMAIN 3: Reference Standard | |||
| Is the reference standards likely to correctly classify the target condition? | Yes | ||
| Were the reference standard results interpreted without knowledge of the results of the index tests? | Yes | ||
| Low | Low | ||
| DOMAIN 4: Flow and Timing | |||
| Was there an appropriate interval between index test and reference standard? | Yes | ||
| Did all patients receive the same reference standard? | Yes | ||
| Were all patients included in the analysis? | No | ||
| High | |||