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Questioning the Meaning of a Change on the Alzheimer's Disease Assessment Scale-Cognitive Subscale (ADAS-Cog): Noncomparable Scores and Item-Specific Effects Over Time.

ABSTRACT: Longitudinal invariance indicates that a construct is measured over time in the same way, and this fundamental scale property is a sine qua non to track change over time using ordinary mean comparisons. The Alzheimer's Disease Assessment Scale-cognitive (ADAS-Cog) and its subscale scores are often used to monitor the progression of Alzheimer's disease, but longitudinal invariance has not been formally evaluated. A configural invariance model was used to evaluate ADAS-Cog data as a three correlated factors structure for two visits over 6 months, and four visits over 2 years (baseline, 6, 12, and 24 months) among 341 participants with Alzheimer's disease. We also attempted to model ADAS-Cog subscales individually, and furthermore added item-specific latent variables. Neither the three-correlated factors ADAS-Cog model, nor its subscales viewed unidimensionally, achieved longitudinal configural invariance under a traditional modeling approach. No subscale achieved scalar invariance when considered unidimensional across 6 months or 2 years of assessment. In models accounting for item-specific effects, configural and metric invariance were achieved for language and memory subscales. Although some of the ADAS-Cog individual items were reliable, comparisons of summed ADAS-Cog scores and subscale scores over time may not be meaningful due to a lack of longitudinal invariance.

SUBMITTER: Cogo-Moreira H

PROVIDER: S-EPMC8392777 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:The Alzheimer's Disease Assessment Scale-Cognitive (ADAS-Cog) has been used widely as a cognitive end point in Alzheimer's Disease (AD) clinical trials. Efforts to treat AD pathology at earlier stages have also used ADAS-Cog, but failure in these trials can be difficult to interpret because the scale has well-known ceiling effects that limit its use in mild cognitive impairment (MCI) and early AD. A wealth of data exists in ADAS-Cog from both historical trials and contemporary longitudinal natural history studies that can provide insights about parts of the scale that may be better suited for MCI and early AD trials.Using Alzheimer's Disease Neuroimaging Initiative study data, we identified the most informative cognitive measures from the ADAS-Cog and other available scales. We used cross-sectional analyses to characterize trajectories of ADAS-Cog and its individual subscales, as well as other cognitive, functional, or global measures across disease stages. Informative measures were identified based on standardized mean of 2-year change from baseline and were combined into novel composite endpoints. We assessed performance of the novel endpoints based on sample size requirements for a 2-year clinical trial. A bootstrap validation procedure was also undertaken to assess the reproducibility of the standardized mean changes of the selected measures and the corresponding composites.All proposed novel endpoints have improved standardized mean changes and thus improved statistical power compared with the ADAS-Cog 11. Further improvements were achieved by using cognitive-functional composites. Combining the novel composites with an enrichment strategy based on cerebral spinal fluid beta-amyloid (A?(1-42)) in a 2-year trial yielded gains in power of 20% to 40% over ADAS-Cog 11, regardless of the novel measure considered.An empirical, data-driven approach with existing instruments was used to derive novel composite scales based on ADAS-Cog 11 with improved performance characteristics for MCI and early AD clinical trials. Together with patient enrichment based on A?(1-42) pathology, these modified endpoints may allow more efficient clinical trials in these populations and can be assessed without modifying current test administration procedures in ongoing trials.

Project description:BACKGROUND:Development of new treatments for Alzheimer's disease (AD) has broadened into early interventions in individuals with modest cognitive impairment and a slow decline. The 11-item version of the Alzheimer's Disease Assessment Scale-Cognitive subscale (ADAS-Cog) was originally developed to measure cognition in patients with mild to moderate AD. Attempts to improve its properties for early AD by removing items prone to ceiling and/or by adding cognitive measures known to be impaired early have yielded a number of ADAS-Cog variants. Using Alzheimer's Disease Neuroimaging Initiative data, we compared the performance of the 3-, 5-, 11- and 13-item ADAS-Cog variants in subjects with early AD. Given the interest in enrichment strategies, we also examined this aspect with a focus on cerebrospinal fluid (CSF) markers. METHODS:Subjects with mild cognitive impairment (MCI) and mild AD with available ADAS-Cog 13 and CSF data were analysed. The decline over time was defined by change from baseline. Direct cross-comparison of the ADAS-Cog variants was performed using the signal-to-noise ratio (SNR), with higher values reflecting increased sensitivity to detect change over time. RESULTS:The decline over time on any of the ADAS-Cog variants was minimal in subjects with MCI. Approximately half of subjects with MCI fulfilled enrichment criteria for positive AD pathology. The impact of enrichment was detectable but subtle in MCI. The annual decline in mild AD was more pronounced but still modest. More than 90 % of subjects with mild AD had positive AD pathology. SNRs were low in MCI but greater in mild AD. The numerically largest SNRs were seen for the ADAS-Cog 5 in MCI and for both the 5- and 13-item ADAS-Cog variants in mild AD, although associated confidence intervals were large. CONCLUSIONS:The possible value of ADAS-Cog expansion or reduction is less than compelling, particularly in MCI. In mild AD, adding items known to be impaired at early stages seems to provide more benefit than removing items on which subjects score close to ceiling.

Project description:Objective: The objective of the analyses described here was to develop thresholds defining clinically meaningful response on the total and item scores of the 6-item short-form Headache Impact Test (HIT-6) in a population of patients with chronic migraine (CM).Background: The HIT-6 is a short, easily understood, and useful measure of the impact of headache on daily life. Though widely used, limited literature supports a threshold value for clinically meaningful response within individuals over time for the HIT-6 total score and for the item scores, especially in the CM population.Methods: PROMISE-2 is a randomized, double-blind, multicenter study comparing intravenous eptinezumab 100 and 300 mg with placebo for the preventive treatment of CM. Responder definitions for HIT-6 total and items scores using data from PROMISE-2 study were calculated via distribution-based and anchor-based methods. Distribution-based methods included half of the baseline standard deviation and baseline standard error of measurement. The change from baseline to week 12 in HIT-6 scores was assessed using the following anchors: patient global impression of change, reduction in migraine frequency, and change in EuroQol 5 dimensions 5 levels visual analog scale. Values from the literature and PROMISE-2 analyses were plotted against the cumulative distribution function of change values (baseline to week 12) and used to triangulate to empirically support clinically meaningful change definitions for the HIT-6 total and item scores in patients with CM.Results: From the literature, 5 articles provided 7 candidate values for a responder threshold for the HIT-6 total score. From distribution- and anchor-based methods, 5 candidate values were derived from PROMISE-2 data. Using the median of all candidate values, a HIT-6 total score responder definition estimate of -6 (ie, ?6-point improvement in the total score) appears most appropriate for discriminating between individuals with CM who have experienced meaningful change over time and those who have not. For item-level analyses using anchor-based methods, the responder definition for items 1-3 ("severe pain," "limits daily activities," and "lie down") was a 1-category improvement in response (eg, from Sometimes to Rarely); for items 4-6 ("too tired," "felt fed up or irritated," and "limits concentration"), a 2-category improvement in response (eg, from Always to Sometimes) was clinically meaningful.Conclusions: Using a multifaceted, statistically-based approach, the recommended responder definition for the HIT-6 total score in the CM population is a ?6-point decrease, consistent with previous literature. Anchor-based item-level responder thresholds were defined as a decrease of 1 or 2 categories, depending on the item. These CM-specific values will provide researchers and clinicians a means to interpret clinically meaningful change in the HIT-6 total and item scores and may facilitate the measurement of treatment benefits in specific functional domains of the HIT-6.

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Questioning the Meaning of a Change on the Alzheimer's Disease Assessment Scale-Cognitive Subscale (ADAS-Cog): Noncomparable Scores and Item-Specific Effects Over Time.

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