Screening for Dementia in Primary Care (continued)

Appendix. Methods

The RTI-UNC Evidence-based Practice Center (EPC), with members of the U.S. Preventive Services Task Force (USPSTF), sought to clarify issues concerning screening for the dementia syndrome (hereafter, dementia) by performing a systematic review of the relevant scientific literature on this topic.

Analytic Framework

The systematic evidence review examined the evidence for screening for dementia. This summary of the evidence utilizes the information from the systematic evidence review, including the analytic framework. Appendix Figure 1 presents the analytic framework that we used to guide our literature search.

The analytic framework describes the logical chain that must be supported by evidence to link screening to improved health outcomes. Each arrow in the analytic framework represents a "Key Question (KQ)" (Appendix Table 1); we searched systematically for evidence concerning each key question in the analytic framework.

The analytic framework begins on the left side of the figure with a primary care population at risk for dementia and moves to the right. The first key question (represented by the overarching arrow) examines direct evidence that screening improves health outcomes. The health outcomes of interest are improved function (including cognitive, social, and physical); reduced hospitalizations, institutionalizations, and health care visits; fewer behavioral problems; reduced caregiver stress; fewer injuries; and improved health-related quality of life. Since we found no such overview studies, we continued to examine the indirect evidence in the following key questions, represented as linkages in the analytic framework.

KQs 2 and 3 examine the yield of screening, involving both the prevalence of undiagnosed dementia in the population and the accuracy and reliability of various screening tests.

Farther to the right in the analytic framework, KQ 4 examines the efficacy of various pharmacologic treatments, including treatment with antihypertensives or aspirin to prevent the progression of vascular dementia; treatment of people with Alzheimer's disease with cholinesterase inhibitors; and treatment of people with Alzheimer's disease with other drugs, neuroleptics, or antidepressants. KQ 5 examines the effectiveness of nonpharmacologic interventions for patients or caregivers; KQ 6 involves the effect of knowledge about the diagnosis of dementia on family and individual planning.

The critical issue is the efficacy of these treatments among people who would be detected by screening. Many studies examine treatment for people with clinically detected dementia; these are useful only insofar as they allow extrapolation to the efficacy of treatment at detection by screening. Furthermore, arrows 4 through 6 (and Key Questions 4-6) actually imply that the issue of interest is the added efficacy of initiating treatment after screening detection as opposed to initiation after clinical detection.

At the far right in the analytic framework are the health outcomes. In the end, the indirect evidence must allow a reasonable estimation of the magnitude of benefit in these outcomes that is attributable to screening.

At the bottom of the analytic framework is linkage and KQ 7, the issue of the harms of screening (e.g., labeling), and KQ 8, concerning the harms of treatment (e.g., side effects of treatment).

Eligibility Criteria for Admissible Evidence

The EPC staff and Task Force liaisons developed eligibility criteria for selecting the evidence relevant to answer the key questions (Appendix Table 2). For KQ 1, we required a well-conducted RCT of screening of adequate size and length to estimate health outcomes with reasonable accuracy. For KQs 2 and 3, we required either cross-sectional or cohort studies in which screening tests were performed on a primary care or general unselected population compared with an acceptable reference standard. For KQs 4-6, we accepted RCTs of treatments with health outcomes that provided information about the severity of participants with dementia. For KQs 7-8, we required RCTs of screened (or treated) versus non-screened (or non-treated) groups.

Literature Search Strategy, Results, and Review of Abstracts/Articles

The analytic framework and key questions guided our literature searches. We examined the critical literature described in the previous review of this topic by the USPSTF (published in 1996)²⁸ and used our eligibility criteria to develop search terms. We used the search terms to search MEDLINE® and the Cochrane Library for English language articles that met our inclusion criteria and were published between January 1, 1994, and September 1, 2002. We also examined the bibliographies of pertinent articles and contacted experts for other references. When we found that a Key Question could best be answered by older literature, we also examined these studies. When we found that a systematic review used acceptable methods and that its studies met our criteria, we used the review instead of the individual studies. The search strategy and results are shown in Appendix Table 2 and Appendix Figures 1, 2, 3, 4, 5, 6, 7, 8. All searches started with the term "dementia" and then proceeded by adding other terms as appropriate.

The first author and at least one other co-author reviewed all abstracts found through our searches to find those that met eligibility criteria. When either reviewer thought that an abstract might meet criteria, the article was copied for full review. The first author and at least one other co-author reviewed each full article. Those that met eligibility criteria after full review and discussion when necessary were abstracted. We critically appraised each study using criteria developed by the USPSTF³¹. If we found a study or systematic review that met criteria but that contained a methodological flaw that invalidated its findings, we excluded it from further review. Abstracted articles or systematic reviews that met eligibility criteria and had no fatal flaws were entered into predesigned evidence tables (go to Appendix B in the Systematic Evidence Review, Screening for the Dementia Syndrome, on the AHRQ Web site [http://www.preventiveservices.ahrq.gov]).

Development of the Systematic Evidence Review and Summary of the Evidence Article

The authors presented an initial work plan including a provisional analytic framework and key questions to the entire Task Force, and also presented interim reports at subsequent meetings. The Task Force discussed and made important contributions to the review on several occasions. The two Task Force liaisons participated in every phase of the review, including conference calls to discuss critical parts of the evidence.

A draft Systematic Evidence Review (SER) was presented to the Task Force and then sent for broad peer review. The peer review included individual experts in the field, representatives of relevant professional organizations, and representatives of appropriate federal agencies. We made revisions to the evidence review as appropriate after receiving peer review comments. The Task Force reviewed all information and voted on a recommendation. We then put the SER into final form and from it developed the manuscript for journal publication.

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