Quality and Strength of Evidence of the Infectious Diseases Society of America Clinical Practice Guidelines

OBJECTIVE: To describe the distribution and temporal trends of the quality and strength of evidence supporting recommendations in the Infectious Diseases Society of America (IDSA) clinical practice guidelines. METHODS: Guidelines either issued or endorsed by IDSA from March 1994 to July 2009 were evaluated using the IDSA-US Public Health Service Grading System. In this system, the letters A-E signify the strength of the recommendation, and numerals I-III indicate the quality of evidence supporting these recommendations. The distribution of the guideline recommendations among strength of recommendation and quality of evidence classes was quantified. Temporal changes between the first and current guideline version were evaluated. RESULTS: Approximately one-half (median, 50.0%; interquartile range IQR, 38.1%-58.6%) of the recommendations in the current guidelines are supported by level III evidence (derived from expert opinion). Evidence from observational studies (level II) supports 31% of recommendations (median, 30.9%; IQR, 23.3%-43.2%), whereas evidence based on ≥ 1 randomized clinical trial (level I) constitutes 16% of the recommendations (median, 15.8%; IQR, 5.8%-28.3%). The strength of recommendation was mainly distributed among classes A (median, 41.5%; IQR, 28.7%-55.6%) and B (median, 40.3%; IQR, 27.1%-47.9%). Among guidelines with ≥ 1 revised version, the recommendations moved proportionately toward more level I evidence (+12.4%). Consequently, there was a proportional increase in class A recommendations (+11.1%) with a decrease in class C recommendations (-23.5%). CONCLUSIONS: The IDSA guideline recommendations are primarily based on low-quality evidence derived from nonrandomized studies or expert opinion. These findings highlight the limitations of current clinical infectious diseases research that can provide high-quality evidence. There is an urgent need to support high-quality research to strengthen the evidence available for the formulation of guidelines.