Des nouvelles des gros relous (ne concerne pas que les maladies à tiques). :
Medscape Conference Coverage, based on selected sessions at the:
Infectious Diseases Society of America (IDSA) 47th Annual Meeting
From Medscape Medical News
Infectious Disease Treatment Guidelines Weakened By Paucity of
Scientific Evidence
Daniel M. Keller, PhD
November 13, 2009 (Philadelphia, Pennsylvania) — Two separate analyses
presented here at the Infectious Diseases Society of America (IDSA) 47th
Annual Meeting revealed that most of the society's treatment guidelines
are based on expert opinion, nonrandomized trials, and case studies.
Only about 15% of the guidelines are supported by randomized controlled
trials (RCTs), considered the highest level of evidence. Nonetheless,
more than 40% of the guidelines' recommendations were classified as
class A, the strongest level of treatment recommendation, according to
Dong Lee, MD, and colleagues from the Division of Infectious Diseases
and HIV Medicine at Drexel University College of Medicine in
Philadelphia, Pennsylvania.
Between 1994 and April 2009, IDSA issued 68 guidelines on 52 different
topics (there have been 2 more since April). Most were published in
Clinical Infectious Diseases. Of the 52 current guidelines, Dr. Lee's
team analyzed the 30 that followed IDSA's standard grading system to
evaluate the class of clinical recommendations and the strength of the
supporting evidence underlying them.
"Our analysis revealed that more than half were based on expert opinion
or not supported by properly controlled trials," Dr. Lee announced. In
an oral presentation, he reported that the 30 guidelines he analyzed
contained a mean of 47 recommendations (range, 14 to 150).
Recommendations ranged from class A (should always be offered) to class
C (optional). The quality of evidence ranged from level I, consisting of
1 or more properly conducted RCTs, to level III, the opinion of
respected authorities, based on clinical experience. Level II evidence
is derived from 1 or more properly controlled trials without randomization.
The guidelines revealed a total of 589 class A recommendations.
"Ideally, all should be [supported by] level I evidence," Dr. Lee said.
"However, a class A recommendation was supported by level I evidence
only in 25% [of cases]." The rest were based on level II (40%) or level
III (35%) evidence. Of all the guidelines evaluated, a median of 41% of
recommendations were class A, but level I evidence supported them only
14% of the time.
Guidelines for common conditions were often based on fairly strong
evidence. The recommendations that are most supported by level I
evidence are in the guidelines for tropical medicine (41% of
recommendations), intra-abdominal infection (39%), and asymptomatic
bacteriuria (38%). "Influenza or Group A Streptococcus guidelines had
less than 20% of level III evidence," possibly because of the high
prevalence of these diseases and the ease of designing studies, Dr. Lee
reported.
He explained the lack of RCTs for some conditions, saying that certain
infections occur rarely or present in heterogeneous forms, making it
difficult to design a study. Furthermore, in some cases it might be
unethical to conduct such a trial, and at times certain knowledge based
on sound clinical judgment will never be tested in RCTs. Finally,
funding to do trials might be lacking.
"Although a randomized controlled trial is referred to as level I
evidence, not all RCTs are created equal," he warned. "Some choose
surrogate markers, others choose patient-centered outcomes.
Well-designed nonrandomized trials may provide more information than
certain randomized controlled trials, but I do think that a randomized
controlled trial minimizes bias and does deserve the high levels of
evidence."
Dr. Lee summarized his presentation, saying that of the 1408 guideline
recommendations he reviewed, "more than half were based on level III
evidence, which is from expert opinion or not supported by properly
controlled trials. Level I evidence was only 15%." He said his study
should help to point out where evidence is lacking and to suggest areas
for further research.
Physicians and trainees should not just look at guidelines, but should
also examine the strength of the evidence on which they are based, he
advised. "When clinicians are using the guidelines, they should not
assume that they are all based on well-designed studies. . . .
Clinicians should remain cautious when using current guidelines as the
sole source for guiding patient care."
A second presentation supported the findings of Lee and coworkers. Abdur
Khan, MD, assistant consultant at King Fahad Medical City in Riyadh,
Saudi Arabia, presented his results in a poster session. Of the 65 IDSA
guidelines, encompassing 6667 recommendations, issued between March 1994
and July 2009, he and his colleagues evaluated the 44, comprising 4206
recommendations, that were posted on the IDSA Web site at the end of July.
They, too, found that, overall, the strength of the recommendations did
not correlate with the available evidence. Level I evidence was the
basis for only 15% of the guidelines, which is in agreement with the
findings that Lee and colleagues reported. Thirty percent of the
evidence was level II.
"Around 55% of the guidelines had a level of evidence of III, which was
based on expert opinion," Dr. Khan told Medscape Infectious Diseases,
"but the class C recommendations [are] only 12%." Guidelines for the
treatment of fungal infections had the weakest supporting evidence;
46.5% to 89.5% of the recommendations were based on level III evidence.
Although the highest levels of evidence generally led to class A
recommendations (25.9%), these strongest recommendations were most often
based on lesser levels of evidence (36.3% on level II; 37.8% on level III).
Commenting on the studies' findings, Richard Whitley, MD, professor of
pediatrics, microbiology, medicine, and neurosurgery at the University
of Alabama at Birmingham and president of IDSA, told Medscape Infectious
Diseases that "one always has to be concerned when we don't have
randomized controlled trials that provide evidence-based medicine to
write guidelines. Without a shadow of a doubt, the best evidence comes
from controlled clinical trials that are adequately powered with a
sample size to answer the targeted question." But he noted that
sometimes expert opinion or small uncontrolled studies have to suffice
if there are not enough patients to conduct better trials.
In some situations, less than level I data can be powerful, Dr. Whitley
observed. He cited the example that neuraminidase inhibitors can
decrease mortality from influenza in elderly individuals. This finding
was based on retrospective reviews of databases of Kaiser Permanente and
other managed health care systems, he explained.
Looking forward, he said, "guidelines don't necessarily just teach how
to take care of patients. They identify areas for future investigation .
. . because they tell us where the vagueness is and where we have to
move forward." This information can then be brought to the attention of
the leadership of the National Institute of Allergy and Infectious
Diseases so that they can fund studies and to the attention of the US
Food and Drug Administration, which has funds to study targeted issues.
Dr. Whitley emphasized that "guidelines shouldn't be just for patients
in the United States. They should be for patients around the world." As
such, IDSA and the European Congress of Clinical Microbiology and
Infectious Diseases will try to work on guidelines together, and IDSA
will also work with Canadian colleagues "so that we can provide a level
of care that's standardized around the world," he said. "Certainly,
that's optimistic."
Neither of these studies received funding. Dr. Lee and Dr. Khan have
disclosed no relevant financial relationships. Dr. Whitley reports being
on the board of directors of Gilead Sciences and is a consultant for 3-V
Biologics and Chimerix; his other consulting, review, advisory panel
positions, investigator, or speaker honoraria relationships include
Juvaris, Primus, Inhibitex, and JID.
Infectious Diseases Society of America (IDSA) 47th Annual Meeting:
Abstract 1324. presented November 1, 2009; Abstract LB-31, presented
October 31, 2009.