1 / 31

Critical Appraisal of the Clinical Literature: The Big Picture

Critical Appraisal of the Clinical Literature: The Big Picture. Cynthia R. Long, PhD Associate Professor Palmer Center for Chiropractic Research. Outline. Overall purpose of critical appraisal Consider “levels of evidence” Some tips on interpreting “significant” findings

royal
Download Presentation

Critical Appraisal of the Clinical Literature: The Big Picture

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Critical Appraisal of the Clinical Literature: The Big Picture Cynthia R. Long, PhD Associate Professor Palmer Center for Chiropractic Research EBC course 10 April 2003

  2. Outline • Overall purpose of critical appraisal • Consider “levels of evidence” • Some tips on interpreting “significant” findings • Potentially useful references

  3. Overall Purpose • To critically appraise a research article in order to assess the validity of the authors’ conclusions

  4. Sections of an Article • Introduction: Background and explanation of rationale for study. • Methods: How was study done? Should allow study to be replicated. • Results: Report results (data). • Discussion: Interpret results. Draw conclusions from results. • Abstract: Article summary.

  5. Recommendation • Read the abstract last when familiarizing yourself with critically appraising the literature. • Assess evidence from reading the article, not the abstract. • Read the abstract in deciding whether or not you are interested in the topic of the article.

  6. Critical Appraisal • similar across types of studies for Introduction and Discussion sections • information in Methods sections may differ • information in Results sections may differ

  7. Overall Questions to Ask • Is the study design appropriate to address the research question? • In the Discussion Section: Are the findings... • ...consistent with the research question of the study?

  8. Terminology: Types of Clinical Studies • Risk • Diagnostic • Prognostic • Intervention

  9. Terminology:Clinical Intervention Studies • Evaluates which treatment interventions are most useful and effective for a given clinical condition

  10. Clinical Intervention Studies • One-group Pre/post Study • Pilot RCT • Randomized Clinical Trial (RCT) • Systematic Review of RCTs

  11. Levels of Evidence

  12. Is the study design appropriate to address the research question? In the Discussion Section: Are the findings... ...consistent with the research question of the study? Levels of Evidence

  13. One-group pre/post design • Addresses: do patients improve after treatment? • Can’t address: is treatment effective for patients? • No comparison group • Patients may improve: natural course of condition, in study, change in lifestyle, treatment

  14. One-group pre/post design: Example Hawk C, Long CR, Azad A. Chiropractic Care for Women with Chronic Pelvic Pain: A Prospective Single-Group Intervention Study. JMPT 1997;20:73-79. • Results: women improved! • Conclusion: needs further study

  15. Pilot RCT • Addresses: is the RCT feasible? • Can’t address: is treatment effective for patients? • Not powered (i.e. sample size not large enough) • Note: often only published if RCT is determined to be unfeasible

  16. Pilot RCT: Example 1 Hawk C, Long CR, et al.Issues in planning a placebo-controlled trial of manual methods: Results of a pilot study. J of Alt Comp Med 2002;8:21-32. • Results: recruitment not feasible; standardization of treatment protocol difficult among multiple sites • Conclusion: put on hold

  17. Pilot RCT: Example 2 Bronfort G, et al.Nonoperative treatments for sciatica: A pilot study for a randomized clinical trial. JMPT 2000;23:536-544. • Results: recruitment not feasible! • Conclusion: put on hold

  18. RCT • Addresses: is the treatment effective for patients? • Caveats: • Must be a powered study • sample size must be formally justified in the Methods section (based on: effect size—minimally important clinical difference; variability of outcome measure; statistical test)

  19. RCT: Example Hurwitz E, et al.A randomized trial of chiropractic manipulation and mobilization for patients with neck pain: Clinical outcomes from the UCLA neck-pain study. Am J Public Health 2002;92:1634-1641. • Results: no statistically or clinically significant differences among groups • Conclusion: cervical spine mobilization is as effective as manipulation in reducing neck pain and related disability among chiropractic patients

  20. Overall Questions to Ask • In the Discussion Section: Are the findings... • ...consistent with the research question of the study? • …consistent with the results presented? • …given in the context of current evidence?

  21. Systematic Review of RCTs • Addresses: is the treatment effective for patients? • Looks at all RCTs of the treatment for patients and combines based on quality of original RCTs

  22. RCT: Example Bronfort G, et al.Efficacy of Spinal Manipulation for Chronic Headache: A Systematic Review. JMPT 2001;24:457-466. • Conclusions: can’t make firm conclusions (few trials of adequate methodological quality)

  23. RCT: Example • Conclusions: • Cervicogenic: SMT better effect than massage • Tension-type and migraine: SMT effect comparable with commonly used first-line prophylactic prescription meds

  24. Terminology: Descriptive Statistics (Results) • Patient characteristics at baseline • Examples: mean, standard deviation, median, range, percentage • Assess group comparability on baseline characteristics • Assess generalizability of results to target population

  25. Terminology: Analytical Statistics (Results) • Assess statistical significance with confidence intervals and p-values • Within and between group differences • Make inference about target population • Must be appropriately interpreted in the context of the research question and the study design

  26. Terminology • P-values and confidence intervals: • Reflects measure of effect relative to variation and sample size

  27. Interpreting p-values: p<0.01  statistically significant difference! 0.01p0.05  statistically significant difference 0.05<p0.10  borderline statistically significant difference p>0.10  no statistically significant difference Statistical Significance

  28. jargon term… Need to consider BOTH statistical and clinical significance “Significant” Findings

  29. i.e. clinical importance is defined before study is conducted assessed with descriptive statistics (e.g. mean improvement in outcome measure) Clinical Significance

  30. statistically and clinically significant findings clinically significant, but not statistically significant statistically significant, but not clinically significant Possible Scenarios

  31. Critical Appraisal References • Useful? It depends… • BMJ series available for free on bmj.com • JAMA articles? • Chiropractic Research Review

More Related