We thank Dr Hopp for her thoughtful response to our editorial and appreciate the opportunity to clarify our position and expand this topic. We agree that the best evidence for practice emerges when multiple high-quality studies are available. We are hopeful that the emerging emphasis on comparative effectiveness research will further inform clinical care of critically ill patients.
Many research groups have published schema for determining strength of evidence (for example, the Agency for Healthcare Research Quality in the United States1 and the Centre for Evidence-based Medicine in Oxford, UK2). The American Association of Critical-Care Nurses’ schema for levels of evidence can be found as part of each Practice Alert,3 and a newly revised version is published in this issue of the American Journal of Critical Care.4 There is wide agreement that systemic reviews and meta-analyses provide the strongest evidence base for clinical decisions....