Therapy: Critical Appraisal Part 2 (Interpreting Results)

  • Kameshwar Prasad


This chapter deals with the second part of the critical appraisal. We want to know: ‘How good is the treatment?’ We would love to have one sentence with one figure to answer this question, but in life, one figure is not enough to tell the whole story about many things. For example, we ask our children: How good are your marks? If he says 99 %, we feel happy. But then soon we want to know, is it the best in the class – in other words, what is his/her position relative to the other students. How many students have marks below this? How many have marks above this? This is to know his relative position. This is described in terms of percentile. The per cent of marks in absolute terms is 99, but it is possible that most students had it (the exam was very easy). Some testing services use per cent, percentile, grade (A1, A2, B1, etc.) and GPA (grade point average) to describe the results. Each figure may give a different perspective and may appeal to different constituencies. This is why stock markets always use at least two figures to describe what happened on the day: usually one to describe the difference in actual figures (absolute difference) and one to describe it in per cent terms (relative to the opening figure).


Relative Risk Risk Ratio Grade Point Average Unfavourable Outcome Relative Risk Reduction 
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Further Reading

  1. Guyatt G, Rennie D, editors. User’s guides to the medical literature: a manual for evidence-based clinical practice. Chicago: AMA Press; 2002. ( Scholar
  2. Laupacis A, Sackett DL, Roberts RS. An assessment of clinically useful measures of the consequences of treatment. N Engl J Med. 1988;318:1728–33.PubMedCrossRefGoogle Scholar
  3. Malenka DJ, Baron JA, Johansen S, Wahrenberger JW, Ross JM. The framing effect of relative and absolute risk. J Gen Intern Med. 1993;8:543–8.PubMedCrossRefGoogle Scholar
  4. Naylor CD, Chen E, Strauss B. Measured enthusiasm : does the method of reporting trial results alter perceptions of therapeutic effectiveness? Ann Intern Med. 1992;117:916–21.PubMedCrossRefGoogle Scholar
  5. Peto R, et al. Design and analysis of randomized clinical trials requiring prolonged observation of each patient. II. Analysis and examples. Br J Cancer. 1977;35:1–39.PubMedCrossRefGoogle Scholar

Copyright information

© Springer India 2014

Authors and Affiliations

  • Kameshwar Prasad
    • 1
  1. 1.Department of Neurology Neurosciences Centre, and Clinical Epidemiology UnitAll India Institute of Medical SciencesNew Delhi DelhiIndia

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