Differences between systematic reviews and health technology assessments: a trade-off between the ideals of scientific rigor and the realities of policy making.

OBJECTIVES: To elucidate important differences between a health technology assessment (HTA) and a systematic review, using an HTA of positron emission tomography (PET) as an example.
METHODS: Interviews with seventeen individuals who were authors or users of the PET HTA.
RESULTS: Those interviewed identified seven areas in which HTAs often differ from traditional systematic reviews: (i) methodological standards (HTAs may include literature of relatively poor methodological quality if a topic is of importance to decision-makers), (ii) replication of previous studies (relatively common for HTAs but not systematic reviews), (iii) choice of topics (more policy oriented for HTAs, while systematic reviews tend to be driven by researcher interest), (iv) inclusion of content experts and policy-makers as authors (policy-makers more likely to be included in HTAs, although there are potential conflicts of interest), (v) inclusion of economic evaluations (more often with HTAs, although economic evaluations based upon poor clinical data may not be useful), (vi) making policy recommendations (more likely with HTAs, although this must be done with caution), and (vii) dissemination of the report (more often actively done for HTAs).
CONCLUSIONS: This case study of an HTA of PET scanning confirms that HTAs are a bridge between science and policy and require a balance between the ideals of scientific rigor and the realities of policy making.