Critical Appraisal

Once you have found the most current evidence, the next step in the EBDM process is to understand what you have and its relevance to your patient and PICO question. One resource available to critically appraise papers consists of a worksheet with structured series of questions that help you determine the strengths and weaknesses of how a study was conducted and how useful and applicable the evidence is to the specific patient problem or question being asked. 1

Key Questions in Appraising the Scientific Literature

In order to become more proficient in judging the evidence, there are appraisal guides to ain in the critical analysis process:

CASP, the Critical Appraisal Skills Programme, offers learning resources including web-based and PDF checklists to appraise Systematic Reviews and Randomized Controlled Trial studies (RCTs).

Several online and print resources provide questions that can be used for reviewing the validity of other types of studies, such as those related to diagnosis, prognosis and harm/etiology as well as studies related to decision analysis, practice guidelines, economic analysis, and qualitative research.

Common Ways Used To Report Outcomes

The structured series of questions found in a checklist provide a guide in appraising the evidence. Once you have determined that the results are valid (the first key question), the next step is to determine if the results, potential benefits (or harms) are important. Sackett et al. identify the clinically useful measures for each type of study.6

For example, in determining the magnitude of therapy results we would expect articles report the control event rate (CER), the experimental event rate (EER), the absolute and relative risk reduction (ARR or RRR) and numbers needed to treat (NNT).

NNT tells us the number of patients (surfaces, periodontal pockets) that would need to be treated with the experimental treatment or intervention to achieve one additional patient (surfaces, periodontal pockets) who has a favorable response.

For diagnostic studies, the sensitivity, specificity and likelihood ratio should be reported.

Critical Appraisal Tools

  1. CASP, Critical Appraisal Skills Programme, Online resource, Systematic Review Checklist. Accessed 3/11/02
  2. Aggressive Research Intelligence Facility [ARIF]. ARIF Critical Appraisal Checklist (for systematic reviews). Accessed 2/27/02.
  3. Oxman AD, Cook DJ, Guyatt GH for the Evidence Based Medicine Working Group. Users' Guides to the Medical Literature, VI. How to use an overview. JAMA 1994;272(17):1367-1371.
  4. Guyatt GH, Sackett DL and Cook DJ for the Evidence Based Medicine Working Group. Users' Guides to the Medical Literature, II. How to use an article about therapy or prevention. JAMA 1993;270:2598-2601, and 271:59-63.
  5. Center for Health Evidence - Users' Guides to Evidence-Based Practice. Complete set of Users' Guides to the Medical Literature originally published by JAMA.
  6. Sackett DL, Straus SE, Richardson WS, Rosenberg W, Haynes RB. Evidence-Based Medicine, How to Practice and Teach EBM, Second Edition, Harcourt, Edinburgh, 2000.
  7. Centre for Evidence-Based Medicine. Downloads and Critical Appraisal Tools.
  8. University of Alberta's Evidence-Based Medicine Toolkit
  9. Centre for Evidence-Based Medicine, Mt. Sinai Hospital
  10. Consort Statement Form for analysis of a RCT
  11. Quorom Statement Form for Analysis of a Meta-Analysis or Systematic Review

 Click here for additional Critical Appraisal resources.