It is well recognized that guidelines become out of date and therefore require updating. We have previously argued that there were six situations (Table
2) that might necessitate the updating of a clinical practice guideline[
8]. Changes in the values placed on outcomes often reflect societal norms. Measuring the values placed on outcomes and how these change over time is complex and has not been systematically studied. When changes occur in the availability of resources for health care or the costs of interventions, a generic policy on updating is unlikely to be helpful, because policy makers in disparate health care systems consider different factors in deciding whether services remain affordable. Most effort has been directed towards defining when new information on interventions, outcomes and performance justifies updating guidelines. This process includes two stages: 1) identifying significant new evidence, and 2) assessing whether the new evidence warrants updating. Within any individual guideline it is possible that there will be some recommendations that are invalid whilst others remain current. A guideline on congestive heart failure[
9] for example, includes 37 individual recommendations. How many must be invalid to require updating the whole guideline? Clearly a guideline needs updating if the majority of recommendations are out-of-date, with new evidence demonstrating that the recommended interventions are inappropriate, ineffective, or superseded by new interventions. In other cases a single, outdated recommendation could invalidate the entire document. Judgments about whether a guideline needs updating are inherently subjective and reflect the clinical importance and number of invalid recommendations. Shekelle and colleagues described an operational method based on their conceptual model, presented above, in relation to the need for updating of 17 clinical guidelines published by the Agency for Healthcare Research and Quality[
10]. They found that seven guidelines were so far out of date that a major update was required, an additional six guidelines required a minor update, three guidelines were still valid, and for one guideline they could reach no conclusion. They concluded that as a general rule, guidelines should be re-evaluated no less frequently than every three years. In an evaluation of the need for updating systematic reviews, Shojania and colleagues found that almost one quarter of systematic reviews are likely out-of-date at two years post-publication[
11]. This method provided a way of balancing the resources required for updating with the potential benefits assuming that a full re-development of a guideline on each occasion was not necessarily an efficient use of resources. Gartlerhner and colleagues[
12] explicitly addressed this issue when they compared this method (which they termed the review method) with a “traditional” method of updating (comparable to de novo guideline development) across six topics from the 1996 US Preventive Services Taskforce Guide to Clinical Preventive Services in terms of the completeness of study identification, the importance of any studies that were missed by either method and the effort involved in the methods. Their results showed that “Although the review approach identified fewer eligible studies than the traditional approach, none of the studies missed was rated as important by task force members acting as liaisons to the project with respect to whether the topic required an update. On average, the review approach produced substantially fewer citations to review than the traditional approach. The effort involved and potential time saving depended largely on the scope of the topic”. On the basis of this they concluded that
“The revised review approach provides an efficient and acceptable method for judging whether a guideline requires updating”.
Table 2
Situations that might necessitate the updating of a clinical practice guideline
1. Changes in the evidence on the existing benefits and harms of interventions: |
2. Changes in the outcomes considered important: |
3. Changes in the available interventions: |
4. Changes in the evidence that current practice is optimal: |
5. Changes in the values placed on outcomes: |
6. Changes in the resources available for health care: |
A description of updating in a cancer guidance program[
13] concluded that for their purposes that a more frequent, three monthly, literature search was needed though they found that the productiveness of this varied across different guidelines.
These issues have been enshrined within the processes of some guideline development programs and in the UK the National Institute for Health and Clinical Excellence (NICE) recommends a combination of literature searching and professional opinion to inform the need for a “full” or “partial” updates and describes its processes for these - though they involve both changes in the evidence relating to a guideline and extensions of the scope of a guideline (changes in the outcomes considered important or available interventions). The assessment of the need for an update happens every three years. In the National Guideline Clearinghouse, guidelines are required to have been re-examined every three years.