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Shekelle PG, Ortiz E, Rhodes S, et al. Validity of the Agency for Healthcare Research and Quality Clinical Practice GuidelinesHow Quickly Do Guidelines Become Outdated?. JAMA. 2001;286(12):1461–1467. doi:10.1001/jama.286.12.1461
Context Practice guidelines need to be up-to-date to be useful to clinicians.
No published methods are available for assessing whether existing practice
guidelines are still valid, nor does any empirical information exist regarding
how often such assessments need to be made.
Objectives To assess the current validity of 17 clinical practice guidelines published
by the US Agency for Healthcare Research and Quality (AHRQ) that are still
in circulation, and to use this information to estimate how quickly guidelines
Design, Setting, and Participants We developed criteria for defining when a guideline needs updating,
mailed surveys to members of the original AHRQ guideline panels (n = 170;
response rate, 71%), and searched the literature for evidence through March
2000 (n = 6994 titles yielding 173 articles plus 159 new guidelines on the
Main Outcome Measures Identification of new evidence calling for a major, minor, or no update
of the 17 guidelines; survival analysis of the rate at which guidelines became
Results For 7 guidelines, new evidence and expert judgment indicated that a
major update is required; 6 were found to be in need of a minor update; 3
were judged as still valid; and for 1 guideline, we could reach no conclusion.
Survival analysis indicated that about half the guidelines were outdated in
5.8 years (95% confidence interval [CI], 5.0-6.6 years). The point at which
no more than 90% of the guidelines were still valid was 3.6 years (95% CI,
Conclusions More than three quarters of the AHRQ guidelines need updating. As a
general rule, guidelines should be reassessed for validity every 3 years.
Considerable effort and resources have been expended internationally
during the past decade on development and dissemination of clinical guidelines.1 Many authorities have emphasized that guidelines are
not valuable to clinicians unless they are up-to-date and present current
scientific knowledge.2 Some guidelines specify
an arbitrary prescheduled review date. The National Guidelines Clearinghouse
will not retain guidelines in their database unless they have been developed,
reviewed, or revised within the last 5 years.3
The limitations of an arbitrary date for scheduled review include wasted resources
if a full update is undertaken prematurely within a slowly evolving field.
Conversely, guidelines in a rapidly evolving field may become outdated before
the scheduled review. Some guidelines state that they should be updated when
new information becomes available; however, we are unaware of any published
attempts to clarify the criteria that define this "new information" or the
methods for gathering it. To our knowledge, empirical data about the rate
at which clinical practice guidelines become obsolete and practical methods
for assessing guidelines for current validity are not available.
The US Agency for Healthcare Research and Quality (AHRQ; formerly the
Agency for Health Care Policy and Research) facilitated development of 19
clinical practice guidelines, 17 of which were still in use in 2000, when
this study was undertaken. These guidelines cover a broad range of topics,
including acute and chronic conditions, illnesses of children and adults,
geriatric syndromes, and rehabilitation. The AHRQ guidelines were developed
using a combination of systematic literature synthesis and multidisciplinary
expert panels and were perceived to have advanced significantly the science
of practice guideline development.2 These guidelines
were considered to represent state-of-the-art management of the selected conditions.
Several years have elapsed since the AHRQ clinical practice guidelines
were developed. At the request of and with support from the agency, we undertook
a systematic assessment of the current validity of these guidelines. We used
these data to provide empirical estimates of the rate at which guidelines
Our first task was to develop a conceptual model for assessing the validity
of existing practice guidelines. No attempt to define the underlying criteria
on which to base decisions about the current validity of guidelines has been
published, nor does an operational method exist for doing so. A complete description
of our conceptual model and its implications is described elsewhere.4
In brief, we identified 6 situations that may require a guideline to
be updated (or withdrawn), including changes in (1) the available interventions,
(2) the evidence on the benefits and harms of existing interventions, (3)
the outcomes that are considered important, (4) the evidence that current
practice is optimal, (5) the values placed on outcomes, and (6) the resources
available for health care.
In assessing the current validity of AHRQ guidelines, we focused on
identifying when new information on interventions, outcomes, and performance
justifies changing a guideline. Changes in the values placed on outcomes occur
as societal norms change. Measuring these values and how they change over
time is complex and is not dealt with herein, nor are changes in the availability
of resources for health care or the costs of interventions, since policymakers
in disparate health care systems consider different factors when deciding
whether services remain affordable.
Identifying new information on interventions, outcomes, and performance
that justifies changing a guideline involves 2 stages: identifying significant
new evidence and assessing whether the new evidence warrants updating. Ideally,
the most thorough way to identify significant new evidence would be to conduct
a new systematic review. Our mandate, however, was to devise an approach that
could be operationalized feasibly for larger numbers of guidelines. On that
scale, conducting a systematic review for each guideline would be too costly
and time consuming—it would be tantamount to completing the first step
of updating, rather than determining whether updating was even necessary.
The AHRQ currently spends approximately $250 000 to conduct a systematic
review through its Evidence-Based Practice Center program; it would have therefore
cost more than $4 million to perform one for each of the 17 guidelines that
were still in use.
We therefore used a combination of a focused literature search and the
guidance of experts from relevant disciplines as a more pragmatic way to help
identify potentially significant new evidence. We reasoned that evidence sufficient
to invalidate an existing national practice guideline would, in general, be
of such a magnitude that it is known to experts in the field or would have
been published in significant articles in major general interest or specialty
medical journals. Our model for assessing the current validity of AHRQ guidelines
is outlined in Figure 1.
We requested the assistance of each of the chairs of the original AHRQ
clinical practice guideline expert panels in identifying the members of their
panel whom they believed were most qualified to assess the current validity
of each of the individual guideline statements within their respective clinical
practice guidelines. Guideline statements were considered to be those set
off in the document in bold, in a box, or as a bulleted point in the "recommendations
for care" section. We used this information to assign individual guideline
statements to these experts, who were then sent a survey that assessed the
statements' current validity. For each guideline statement, we asked 3 questions:
(1) "Are you aware of new evidence or developments in the field relevant to
this guideline statement?" (2) "Is the new evidence or development of sufficient
importance to invalidate the guideline statement?" and (3) "Are there new
guideline statements (within the boundaries of the original guideline) that
should be present?" Respondents were told to consider validity within the
context of our conceptual model (eg, changes in the available interventions,
changes in the evidence on the benefits and harms of existing interventions).
A second round of mailings was sent to nonrespondents. Respondents were given
no financial incentives to reply. For each clinical practice guideline, we
also attempted to obtain an evaluation of validity from at least 1 expert
not associated with the original practice guideline panel.
We conducted limited literature searches for significant new evidence
that may have an effect on the validity of the guideline statements. These
limited literature searches were restricted, using the "document type" Medical
Subject Heading terms to retrieve only review articles, editorials, and commentaries
published through March 2000 on the particular guideline topic. Our reasoning
for this restriction was that new evidence that is sufficient to change practice
would frequently be accompanied by an editorial or commentary, making the
latter a sentinel marker for new evidence. We further restricted the search
to key journals, ie, those most likely to have published evidence of sufficient
magnitude to warrant the revision of an existing national practice guideline.
Key journals included the 5 major general interest publications (Annals of Internal Medicine, British Medical Journal, JAMA, The Lancet, and New England Journal of Medicine) and key specialty journals for each
topic identified by local experts in the field. For some guidelines, we did
not identify key specialty journals and, therefore, conducted searches unrestricted
We defined the ideal starting point for each search as the end date
for the original AHRQ guideline search. Only 5 (29%) of the 17 guidelines,
however, identified this date. For the remainder, we conservatively chose
the starting point to be 2 years prior to the publication date of the guideline;
in the 5 guidelines for which we did have data, this was the lag period between
the end of the search and publication. Two reviewers (P.G.S. and E.O.) reviewed
the literature searches. Titles, abstracts, and articles were reviewed sequentially,
seeking new evidence regarding the guideline statements. New evidence (principally
randomized clinical trials) referenced in the review articles, editorials,
or commentaries was retrieved and reviewed for relevance.
To assess the current validity of the AHRQ guideline statements, we
also searched for practice guidelines that had been published after the release
of the original AHRQ documents and that were related to the same conditions.
We used the National Guideline Clearinghouse (http://www.guidelines.gov) and the Web sites of publishing organizations to identify relevant
materials, downloading either the full text or the summary statements provided
by the National Guideline Clearinghouse.
We identified additional evidence from the responses to our survey.
For each guideline statement judged invalid for which supporting evidence
was referenced, these references were retrieved.
The process described identified evidence about the current validity
of the individual statement within each guideline. To make a judgment about
retaining or withdrawing the entire guideline, we reviewed all of the evidence
for each guideline. We considered the studies identified and the responses
of the experts to the survey questions about validity and new guideline statements.
We also placed greater emphasis on new evidence regarding the principal diagnostic
or therapeutic procedures that have a major impact on outcomes (eg, mortality).
Based on these sources and our judgment, we assigned the guidelines into 1
of 3 categories.
Major Update Required. New evidence called into question 1 or more principal diagnostic or
therapeutic recommendations or new evidence suggested the need for new principal
diagnostic or therapeutic guideline recommendations. A major update of the
guideline or its withdrawal from circulation is warranted.
Minor Update Required. The principal diagnostic or therapeutic recommendations were still valid,
but new evidence supported changes to other recommendations or greater refinement
of existing recommendations. A minor update of the guideline is warranted.
Still Valid. The recommendations remain valid; no update is warranted.
Next, we conducted a survival analysis of the AHRQ guidelines to estimate
the rate at which guidelines become outdated. For each guideline, we determined
a date of "birth"; that is, when work on the guideline was completed. We also
determined whether the guideline had "died" by the time we reviewed it (April
2000). If so, we determined the date of "death," and if not, we treated the
observation as right-censored with a lifetime at least as long as the time
from birth to April 2000.
For all 19 original guidelines, we defined birth as 12 months prior
to the publication date of the guideline (which approximates the date when
the completed guideline was delivered to the AHRQ). Three guidelines had dates
of death corresponding to when they were withdrawn or had updates initiated
by the AHRQ or the US Public Health Service (human immunodeficiency virus
infection, smoking cessation, and urinary incontinence). For guidelines judged
to require updating, we assumed conservatively that their deaths occurred
in April 2000. This assumption is conservative because their actual lifetimes
were of that length or less; hence, our lifetime estimates are biased positively.
To estimate the survival curve, we first fit a nonparametric Kaplan-Meier
curve to this lifetime data set of censored and uncensored observations. We
also fit a parametric model assuming that the survival function followed the
Weibull distribution.5 Both of these methods
take into account that some observations are censored in that the true lifetimes
of 3 of the guidelines are unknown. This analysis was conducted using S-PLUS
statistical analysis software.6
Of the 19 clinical practice guidelines for which development was facilitated
by the AHRQ, we assessed the 17 shown in Table 1. The urinary incontinence guideline underwent an update
in 1996 to provide more specific recommendations; we consider only this 1996
update in our assessment of current validity. The AHRQ withdrew the human
immunodeficiency virus guideline in October 1999 because the AHRQ judged it
to be invalid. Similarly, the smoking cessation guideline recently underwent
a Public Health Service–sponsored update.7
We received replies from the panel chairs for 15 of the 17 clinical
practice guidelines identifying whom among their respective panel members
should be contacted to assess the current validity of their practice guideline
statements. For 1 of the 2 practice guidelines for which we did not receive
this information, we contacted the evidence-based practice center that had
participated in the AHRQ-sponsored literature review that was used in the
specialty society–sponsored guideline update process and asked the appropriate
member of the task order team to complete the survey. For the remaining clinical
practice guideline, 1 of the authors coincidentally had participated in the
original guideline development process and decided which statements to send
to which experts.
We were unable to attain current contact information for 4 of the recommended
experts, and in 2 instances, the panelists were deceased. We then sent out
the individual guideline statements to the respective experts (n = 175). Five
surveys were returned with the notation that the panelist was no longer at
the given address and no forwarding address was known. Of the remaining 170
surveys, 121 (71%) were returned. Four panelists explicitly declined to participate
in the survey. The number of responses varied by guideline. For all but 3
guidelines, more than 60% of the surveys were returned. We were also able
to obtain assessments of the validity of the practice guideline statement
from 8 nonpanel experts for 7 of the guidelines. Among all questions about
validity or the need for new recommendations across guidelines, there was
complete agreement among respondents for 71% of questions, and only 5% of
questions had more than 1 dissent.
Our focused literature searches identified 6994 titles. From these titles,
610 were selected for abstract review based on their potential for providing
new information relating to the respective guideline areas. Of these, 173
full-text articles were identified and reviewed. In addition, 159 guidelines
were also retrieved and reviewed. Experts identified an additional 156 references,
so a total of 766 abstracts and 208 articles were reviewed.
Table 1 lists our classification
for each AHRQ guideline along with a succinct description of the key evidence
on which we based our decision. The new evidence in Table 1 is not a complete recapitulation of all that was identified
but shows the evidence that was most influential in making classifications.
In all, we found that 7 guidelines needed a major update; 3 guidelines were
still valid; and 6 guidelines needed a minor update. For 1 guideline (quality
determinants of mammography), we reached no conclusion because we had an insufficient
response rate to our survey and were unable to adequately interpret the highly
technical literature regarding possible improvements in mammographic imaging.
Figure 2 shows the Kaplan-Meier
survival curve for the AHRQ guidelines. The solid line shows the estimated
proportion of guidelines that survive at each point (ie, that have lifetimes
at least as long as the horizontal time in years), with dashed lines representing
the 95% confidence interval (CI) bounds. The Weibull parametric model produced
estimates similar to the nonparametric approach, and we used the former to
construct estimates and 95% CIs for certain survival deciles. Table 2 shows the Weibull model estimates for lifetimes of certain
proportions (eg, 50% of the guidelines will survive at least 5.8 years [95%
CI, 5.0-6.6 years]). A sensitivity analysis using only guidelines judged as
requiring a major update (death) yielded a 90% survival estimate of 5.5 years
(95% CI, 4.5-6.5 years) and a 50% survival estimate of 7.1 years (95% CI,
Of the 17 clinical practice guidelines developed under the auspices
of the AHRQ between 1990 and 1996, we determined that more than three quarters
need updating. This finding provides the first empirical evidence of the rate
at which a collection of well-constructed clinical practice guidelines go
out-of-date. Our survival analysis estimated that half of the guidelines became
obsolete in 5.8 years. This estimate must be considered an upper bound since
some of the guidelines in this cohort certainly became obsolete earlier than
April 2000, the date of the judgment in our study. It is tempting to try to
more precisely estimate the date when these guidelines became outdated by
using the publication date of the new evidence used to reach the decision
about validity. However, determinations of guideline validity require both
evidence and judgment, and we did not collect judgments earlier than March
2000. We refrained from making assumptions about judgment at earlier points.
Our study has implications for the developers and users of clinical
practice guidelines. Guidelines should be reviewed regularly to assess whether
they are up-to-date. Given that our estimates of the lifetime of validity
represent upper bounds, we believe that the best interval to recommend for
this assessment is a conservative one—3 years, the lower bound of the
95% CI for the period when 90% of the guidelines were estimated to be still
valid. A shorter interval may be indicated for topics noted for rapid scientific
advances and a longer interval for fields that are more stable. Given the
limited sample size in our study, we cannot provide estimates of survival
stratified this way.
Our study also yielded important lessons about the practical methods
to accomplish guideline review. Our combination of focused literature searches
and expert opinion was a feasible way to review the validity of guidelines
without expending considerable resources (approximately $100 000 to assess
17 guidelines). We consider our work to be only a first step, however, and
further work is needed to better establish the optimal method of limited literature
searches and how this should be integrated with expert judgment.
We found that we were able to identify relevant information from our
limited literature searches in a more expeditious manner for topic areas with
which we were clinically familiar. For topics with which we were unfamiliar,
selecting and retrieving a larger proportion of irrelevant articles (lower
specificity) became necessary to maximize sensitivity. Having the limited
literature searches conducted by groups already familiar with the topic, such
as relevant Cochrane Review groups or evidence-based practice centers, is
likely to be more efficient.
Our search for new evidence would have been more efficient if we had
been able to better target our search. Developers of guidelines could greatly
ease the resources required for subsequent updating if future guidelines described
the type of evidence that they anticipated would play a pivotal role in requiring
revision of a guideline statement.
The relatively high response rate to our survey (without financial incentives)
suggests that it might have been important to the members of the original
guideline expert panels to keep their respective guidelines up-to-date. The
lower response rate we achieved to our survey of experts who were not on the
original guidelines panel indicates that more effort (eg, financial incentives)
may be needed to obtain an acceptable response rate from experts without this
personal investment. Having periodic review by experts who were not involved
with the initial guideline may help protect against perpetuating underlying
bias introduced by the members of the original guideline panel, but it would
come at increased cost.
All of these difficulties may be overcome by considering development
of guidelines an ongoing process rather than a discrete event. Organizations
developing guidelines should consider impaneling guideline groups for a fixed
period, with a rotating membership analogous to a National Institutes of Health
study section. After guideline development, automated literature searching
could be conducted at regular intervals (eg, every 6-12 months) and relevant
citations reviewed by subgroups of the panel. Relevant articles could then
be distributed to the entire panel for consideration of the impact of new
evidence on the validity of the existing guideline, using the criteria we
have articulated. Areas of the guideline judged to be invalid could then be
changed expeditiously if the guidelines were available in electronic form
on the Web. In addition, Web-based availability would facilitate easy replacement
of only those sections of the guidelines judged to be in need of change. Furthermore,
this could be linked through list servers to electronically alert interested
parties that a change has been made. In this way, guidelines would always
be up-to-date and readily available.
Our study has several limitations. First, we assessed a relatively small
number of existing clinical practice guidelines. The National Guideline Clearinghouse
currently contains more than 1050. However, the guidelines we assessed represent
the entire output of a high-profile program to develop national guidelines
on a broad range of topics, which increases the generalizability of our estimates
of shelf life. Second, these guidelines were not selected randomly; they came
from 1 developer with a particular approach to guideline development. Guidelines
that are less rigorously developed may become outdated at a different rate
than what we report here. Third, we could not determine the actual date that
guidelines became outdated, only that they had done so within a certain interval.
This probably overestimates the useful life of these guidelines and is the
reason we used the lower bound of the 95% CI to recommend when a review should
be initiated. Fourth, our method of assessing the current validity of the
guidelines has not been validated against the ideal gold standard: a simultaneous
full update of the guidelines. Until such a comparison is undertaken, the
methods we report here, which appear to have face validity, offer a practical
way to make these determinations with limited resources.
In summary, we found that more than 75% of the AHRQ guidelines developed
between 1990 and 1996 need updating. Half of these guidelines were certainly
outdated in 5.8 years. To keep practice guidelines up-to-date, we recommend
that as a general rule they be reviewed no later than 3 years after completion.
This 3-year rule should be moved forward or backward in time if there is an
expectation that the topic area of a particular guideline is evolving quickly