Alzheimer's disease--clinical trials and the logic of clinical purpose

Model of disablement and recovery: knowledge translation in rehabilitation research and practice

Disablement is a multifactorial and complex process that creates a challenge for both the rehabilitation researcher and the clinical practitioner; however, each seeks to improve quality health outcomes for the adult or child with disability. Knowledge translation (KT) is an approach to evidence-based medicine where various evidence sources are aggregated so that clinical decisions regarding intervention selection and dosing result in beneficial care for an individual. Structural equation modeling was used to test a theoretical model of disablement based on the impairment, activity, and participation categories of the International Classification of Functioning, Disability and Health (ICF) level of functioning. Using available cohort data from a randomized controlled trial of people with poststroke walking disability, exploratory and confirmatory factor analysis revealed that the latent variables-impairment and activity-are separate disablement constructs that limit participation for a person with disability. Path analysis revealed that the direct effect of impairment on participation was not statistically significant; however, the indirect path from impairment to participation through activity was significant (indirect effect). The direct effect of activity on participation was significant. Model assumptions were tested with postintervention data from the same cohort. For people with disability after stroke, the probability that functional tasks could be performed with less effort was greater for those individuals who met or exceeded a physiologic walking threshold after a structured, progressive intervention provided by a physical therapist 6 months earlier. This article discusses how structural equation modeling can be used as a statistical method to explore the causal paths from disability to ability. The knowledge inquiry and synthesis phases of the knowledge-to-action KT framework parallel the essential elements of structural equation modeling; knowledge is created that is theoretically driven, supported by prior research, and analyzed, refined, validated, and tailored to address real-world problems. Using a theoretical framework of disablement with clinical judgment and quantitative research methods, a clinically intuitive model of disablement was validated. The positive dimension is a model of recovery where causal paths lead from disablement to ablement. Innovative approaches in rehabilitation research design along with pragmatic application of research to practice are needed to improve today's health outcomes for people with disability.

Quality of mental health care for nursing home residents: a literature review

Because of the high proportion of nursing home residents with a mental illness other than dementia, the quality of mental health care in nursing homes is a major clinical and policy issue. The authors apply Donabedian's framework for assessing quality of care based on the triad of structure, process, and outcome-based measures in reviewing the literature on the quality of mental health care in nursing homes. Quality measures used within the literature include mental health consultations and hospitalizations, inappropriate use of medications, and mental health survey deficiencies. Factors related to the resident's welfare (nurse staffing), provider norms (locality), and financial factors (payer mix) were associated with the quality of mental health care. Although future research is necessary, the extant literature suggests that persons with mental illness are frequently admitted to nursing homes and their care is often of poor quality and related to a series of resident and facility factors.

Neuropsychiatric clinical trials: should they accommodate real-world practices or set standards for clinical practices?

Evidence-based psychiatry seeks the best research evidence for use in patient care. Recent research suggests that problems with accuracy, precision, bias, and other sources of unreliability potentially interfere with the validity of psychiatry's evidence base. Because many negative clinical research studies go unpublished, awareness and fuller understanding of these problems are blocked by lack of access to relevant data. Based on the importance of scientific soundness of neuropsychiatric research and patient care, we argue for increased attentiveness by investigators and practitioners to how clinical trials (CTs) interdependently estimate the efficacy of treatments and the effectiveness of methods as fair tests of efficacy. Deference by CT investigators to real-world practice conditions at research sites because of the unreliability introduced into data by these practices does not ensure unbiased evaluations of treatment efficacy. We argue for more systematic attention to sources of unreliability in CT investigations and increased commitments to assure the validity of the neuropsychiatric evidence base. These recommendations aim to determine neuropsychiatric drug efficacy with greater certainty to better quantify the clinical importance of drug-associated effects and to provide CT-evidenced guidance for practitioners to most effectively use drug efficacy in patient care.

Why do so many drugs for Alzheimer's disease fail in development? Time for new methods and new practices?

Alzheimer's disease (AD) drug developments and clinical trials (CT) remain vulnerable to problems that undermine research validity. Investigations of CT methods reveal how numerous factors decrease active drug-placebo group differences and increase variance, thereby reducing power to reach statistical significance for outcome measure differences in AD CTs. Such factors include, amongst many, inaccuracy, imprecision, bias, failures to follow or lack of operational protocols for applying CT methods, inter-site variance, and lack of homogeneous sampling using disorder criteria. After a review of the literature and survey of a sample of AD and Mild Cognitive Impairment (MCI) CTs, the authors question whether problems of human error preclude AD researchers from continuing their dependence on rated outcome measures for CTs. The authors propose that the realities of AD, especially a probable irreversible progression of neuropathology prior to onset of clinical symptoms or signs capable of differentiating persons at risk for AD from normal aged, require AD investigators and clinicians to privilege biomarkers and encourage their development as surrogate targets for preventive AD treatment developments, testing, and use in clinical practice.

Mexiletine therapy for chronic pain: survival analysis identifies factors predicting clinical success

Mexiletine, a sodium channel blocker, treats neuropathic pain but its clinical value has been questioned due to its significant side effects and limited efficacy. We hypothesized that ongoing therapy with mexiletine would have limited patient acceptance, but that an analgesic response to intravenous (IV) lidocaine (a pharmacologically similar drug) would identify patients most likely to choose ongoing therapy with mexiletine. We identified a cohort of 37 patients with neuropathic pain who underwent IV lidocaine infusions at our institution and were subsequently prescribed mexiletine. Time until discontinuation of mexiletine was used as the primary endpoint. Time until discontinuation is a clinically relevant, discrete, objective endpoint gaining acceptance as a metric for assessing clinical performance of drugs with significant side effects and limited efficacy. We used the techniques of survival analysis to determine factors that predicted continued therapy with mexiletine. Median time to discontinuation of mexiletine was only 43 days. A stronger analgesic response to IV lidocaine significantly predicted continued acceptance of mexiletine therapy. Decreasing age and male gender also predicted continued acceptance of mexiletine therapy. Analyzing time to mexiletine discontinuation uncovers important limitations in mexiletine's clinical performance missed by studies with conventional endpoints, such as change in pain score. Despite claims of efficacy, acceptance of mexiletine therapy is poor overall. Test infusions with lidocaine identify patients most likely to continue mexiletine therapy. Further work is needed to confirm these results and evaluate the relative acceptance of mexiletine vs. other treatments of neuropathic pain.

Cholinesterase inhibitors in mild cognitive impairment: a systematic review of randomised trials

BACKGROUND

Mild cognitive impairment (MCI) refers to a transitional zone between normal ageing and dementia. Despite the uncertainty regarding the definition of MCI as a clinical entity, clinical trials have been conducted in the attempt to study the role of cholinesterase inhibitors (ChEIs) currently approved for symptomatic treatment of mild to moderate Alzheimer disease (AD), in preventing progression from MCI to AD. The objective of this review is to assess the effects of ChEIs (donepezil, rivastigmine, and galantamine) in delaying the conversion from MCI to Alzheimer disease or dementia.

METHODS AND FINDINGS

The terms "donepezil", "rivastigmine", "galantamine", and "mild cognitive impairment" and their variants, synonyms, and acronyms were used as search terms in four electronic databases (MEDLINE, EMBASE, Cochrane, PsycINFO) and three registers: the Cochrane Collaboration Trial Register, Current Controlled Trials, and ClinicalTrials.gov. Published and unpublished studies were included if they were randomized clinical trials published (or described) in English and conducted among persons who had received a diagnosis of MCI and/or abnormal memory function documented by a neuropsychological assessment. A standardized data extraction form was used. The reporting quality was assessed using the Jadad scale. Three published and five unpublished trials met the inclusion criteria (three on donepezil, two on rivastigmine, and three on galantamine). Enrolment criteria differed among the trials, so the study populations were not homogeneous. The duration of the trials ranged from 24 wk to 3 y. No significant differences emerged in the probability of conversion from MCI to AD or dementia between the treated groups and the placebo groups. The rate of conversion ranged from 13% (over 2 y) to 25% (over 3 y) among treated patients, and from 18% (over 2 y) to 28% (over 3 y) among those in the placebo groups. Only for two studies was it possible to derive point estimates of the relative risk of conversion: 0.85 (95% confidence interval 0.64-1.12), and 0.84 (0.57-1.25). Statistically significant differences emerged for three secondary end points. However, when adjusting for multiple comparisons, only one difference remained significant (i.e., the rate of atrophy in the whole brain).

CONCLUSIONS

The use of ChEIs in MCI was not associated with any delay in the onset of AD or dementia. Moreover, the safety profile showed that the risks associated with ChEIs are not negligible. The uncertainty regarding MCI as a clinical entity raises the question as to the scientific validity of these trials.