D. 重新评估和移动目标问题

卫生技术被评估为移动目标 (Goodman 1996).随着技术的成熟，技术本身的发展或其他因素可能会降低HTA现状对医疗保险政策的效用因此，卫生技术评估（HTA）比一次性分析更多的是迭代过程。引发重新评估的一些因素可能包括：

• 使用该技术的安全性，有效性和其他结果或影响的证据（例如，出版临床试验或新的医疗分析重要结果）
• 技术（技术修改，模型，配方，交付模式等。）
• 适应症（不同健康问题，严重程度等。）
• 使用的群体（不同年龄组，合并症，初级和二级预防等）
• Protocols or care pathways in which the technology is used that may alter the role or utility of the technology
• Care setting in which the technology is applied (inpatient, outpatient, physician office, home, long-term care)
• Provider of the technology (type of clinician, other caregiver, patient, etc.)
• Practice patterns (e.g., large practice variations)
• Alternative technology or standard of care to which the technology is compared
• Outcomes or impacts considered to be important (e.g., quality of life, types of costs)
• Resources available for health care or the use of a particular technology (i.e., raising or lowering the threshold for decisions to use the technology)
• Cost (or price) of a technology or its comparators or of the associated episode or course of care
• Adoption or use of guidelines, payment policies, or other decisions based on the HTA report
• Interpretation of existing research findings (e.g., based on corrections or re-analyses)

There are numerous instances of moving targets that have prompted reassessments. For example, since the inception in the late 1970s of percutaneous transluminal coronary angioplasty (PTCA, approved by the US FDA in 1980), its clinical role in relation to coronary artery bypass graft surgery (CABG) has changed as the techniques and instrumentation for both technologies have evolved, their indications have expanded, and as competing, complementary, and derivative technologies have emerged (e.g., laser angioplasty, bare metal and drug-eluting coronary artery stents, minimally-invasive and “beating-heart” CABG). The emergence of viable pharmacological therapy for osteoporosis (e.g., with bisphosphonates and selective estrogen receptor modulators) has increased the clinical utility of bone densitometry. Long rejected for its devastating teratogenic effects, thalidomide reemerged for carefully managed use in a variety of approved and investigational uses in leprosy and other skin diseases, certain cancers, chronic graft-vs.-host disease, and other conditions (Richardson 2002; Zhou 2013).

While HTA programs cannot avoid the moving target problem, they can manage and be responsive to it. Box VI-5 lists approaches for managing the moving target problem.

Box VI-5. Managing the Moving Target Problem

• Recognize that HTA must have the capacity to revisit topics as needed, whether periodically (e.g., every two or five years) or as prompted by important changes since preparation of the original HTA report.
• Document in HTA reports the information sources, assumptions, and processes used. This “baseline” information will better enable HTA programs and other interested groups to recognize when it is time for reassessment.
• In the manner of a sensitivity analysis, indicate in HTA reports what magnitudes of change in key variables (e.g., accuracy of a diagnostic test, effectiveness of a type of drug, patient adherence rates, costs) would result in a significant change in the report findings.
• Note in HTA reports any known ongoing research, work on next-generation technologies, population trends, or other developments that might prompt the need for reassessment.
• Have or subscribe to a horizon scanning or monitoring function to help detect significant changes in technologies, how they are used, or other developments that might trigger a reassessment.
• Recognize that, as the number of technology decision makers increases and evidence-based methods diffuse, multiple assessments are generated at different times from different perspectives. This may diminish the need for clinicians, payers, and other decision makers to rely on a single, definitive assessment on a particular topic.

Aside from changes in technologies and their applications, even new interpretations of, or corrections to, existing evidence can prompt a new assessment. This was highlighted by a 2001 report of a Cochrane Center that prompted the widespread re-examination of screening mammography guidelines by government and clinical groups. The report challenged the validity of evidence indicating that screening for breast cancer reduces mortality, and suggested that breast cancer mortality is a misleading outcome measure (Olson 2001). More recently, an assessment by the US Preventive Services Task Force of the same issue prompted re-examination of available evidence, the process used by this task force to arrive at its findings, how the findings were transmitted to the public, and how the findings were interpreted by patients and clinicians (Thrall 2010; US Preventive Services Task Force 2009).

Changes in the volume or nature of publications may trigger the need for an initial assessment or reassessment. A “spike” (sharp increase) in publications on a topic, such as in the number of research reports or commentaries, may signal trends that merit attention for assessment. However, in order to determine whether such publication events are reliable indicators of technology emergence or moving targets requiring assessment, further bibliometric research should be conducted to determine whether actual emergence of new technologies or substantial changes in them or their use has been correlated with such publication events or trends (Mowatt 1997).

Not all changes require conducting a reassessment, or that a reassessment should entail a full HTA. A reassessment may require updating only certain aspects of an original report. In some instances, current clinical practices or policies may be recognized as being optimal relative to available evidence, so that a new assessment would have little potential for impact; or the set of clinical alternatives and questions have evolved so much since the original assessment that it would not be useful to update it, but to conduct an entirely new assessment.

In some instances, an HTA program may recognize that it should withdraw an existing assessment because to maintain it could be misleading to users and perhaps even have adverse health consequences. This may arise, for example, when an important flaw is identified in a pivotal study in the evidence base underlying the assessment, when new research findings appear to refute or contradict the original research base, or when the assumptions used in the assessment are determined to be flawed. The determination to maintain or withdraw the existing assessment while a reassessment is conducted, to withdraw the existing assessment and not conduct a reassessment, or to take other actions, depends on the risks and benefits of these alternative actions for patient health, and any relevant legal implications for the assessment program or users of its assessment reports.

Once an HTA program determines that a report topic is a candidate for being updated, the program should determine the need to undertake a reassessment in light of its other priorities. Assessment programs may consider that candidates for reassessment should be entered into the topic priority-setting process, subject to the same or similar criteria for selecting HTA topics.

A method for detecting signals for the need to update systematic reviews was validated for a set of reports produced by the AHRQ Comparative Effectiveness Review program. This method for determining whether a report needed to be updated involved applying the literature search strategy for the original systematic review to five leading general interest medical journals plus four-to-six specialty journals most relevant to the topic. The method also involved providing a questionnaire to experts in the field that requested them to indicate whether the conclusions in the original review were still valid and, if not, to identify any relevant new evidence and citations. This information was used to identify reports to be updated. After the new (i.e., updated) reports were completed, the researchers conducted a systematic comparison of the conclusions of the original and new reports, and found that the determination of priority for updating the original reports was a good predictor of actual changes to conclusions in the updated reports (Shekelle 2014).

Some research has been conducted on the need to reassess a particular application of HTA findings, i.e., clinical practice guidelines. For example, for a study of the validity of 17 guidelines developed in the 1990s by AHCPR (now AHRQ), investigators developed criteria defining when a guideline needs to be updated, surveyed members of the panels that prepared the respective guidelines, and searched the literature for relevant new evidence published since the appearance of the guidelines. Using a “survival analysis,” the investigators determined that about half of the guidelines were outdated in 5.8 years, and that at least 10% of the guidelines were no longer valid by 3.6 years. They recommended that, as a general rule, guidelines should be reexamined for validity every three years (Shekelle, Ortiz 2001). Others contend that the factors that might prompt a reassessment do not arise predictably or at regular intervals (Brownman 2001). Some investigators have proposed models for determining whether a guideline or other evidence-based report should be reassessed (Shekelle, Eccles 2001).

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