Contents
| A users guide Alejandro R Jadad 5 Reporting and interpreting individual trials: the essentials
The extent to which you can interpret the results of a trial depends on several closely related factors, including the following:
This book has been conceived to help you with the first two factors. This chapter will help you to identify the key elements that you should look for in a trial report to interpret its results with confidence. The other three factors - content expertise, statistical knowledge, and time - are likely to vary from reader to reader, and addressing them is obviously beyond the scope of this book. The relationship between trial reporting and interpretation In most cases, the only information that you will have to interpret a trial is what has been published in a journal. Unfortunately, evidence generated during the past 30 years has shown repeatedly that there is a wide gap between what a trial should report to help readers interpret their results and what is actually published.1 Therefore, you should be prepared to find that most reports do not contain all the information that you require to make informed judgments on the internal and external validity of trials. As described in Chapter 4, an international group of clinical epidemiologists, biostatisticians, and journal editors published, in 1996, a statement called CONSORT (Consolidation of the Standards of Reporting Trials),1 the aim of which is to improve the standards of written reports of RCTs and to ensure that readers find in the reports all the information that they require to interpret the trial results with confidence.2 This statement includes a checklist of 21 items and a flow diagram that authors should use to provide information on the progress of patients through a study. The original article in which the CONSORT statement was described was, however, very short and targeted authors of trial reports, not readers.1 In this chapter, I use the CONSORT statement as a template to describe the elements that you should take into account when reading a trial report to interpret its results. I also use information from my own experience as a reader, from three series of articles produced over the past 20 years by members of the Department of Clinical Epidemiology and Biostatistics at McMaster University, and from two recent books on how to read articles.3,4 The series includes articles on how to read clinical journals,5-10 users' guides to the medical literature,11,12 and a series on basic statistics for clinicians.13-16 Table 5.1 and Fig 5.1 provide the information in CONSORT's statement. If you have not read these articles, I strongly encourage you to do so. I would also like to encourage you to get a copy of the books, which are written in friendly, easy-to-follow format. My main challenge in writing this chapter was to keep the discussion of the issues brief and clear, focusing on the essential elements that you, the reader, need to take into account when interpreting the results of an RCT report. My aim is to help you make efficient use of the limited time you can spend reading articles. When appropriate, I expand on issues discussed in previous chapters or refer you directly to the sections of the book where certain items have been discussed in more detail. In addition, I include one or more additional sources of information where you could find detailed explanations of specific issues, particularly statistical ones, which are beyond the scope of this book. What are the key elements of a trial report needed to interpret its results with confidence? To interpret the results of a trial with confidence, regardless of your background, the time you have available to read a trial report, and the reasons why you are reading it, you will have to answer at least the following questions:
In the rest of this chapter, I try to help you answer these questions in a time-efficient manner, pointing out the sections of a report in which the information you need is most likely to be found. I am aware that you may focus on different aspects of a report: if you are a clinician trying to decide whether to use an intervention to study or treat a particular patient; if you are a researcher designing a new RCT; if you are a peer-reviewer or an editor judging whether a trial report should be published in a journal; if you are conducting a systematic review of multiple trials; if you are deciding whether to purchase a service or a new intervention; or if you are a journalist trying to decide whether to report on an article published in the latest issue of a journal. Although I do my best to provide you with enough information to answer the above questions regardless of whom you are or why you are reading a trial report, I have focused primarily on meeting the needs of busy individuals with limited experience in methodology and research. Now, let's try to answer the questions. Is the topic addressed by the trial interesting to you? Usually, all you need to do to establish if a report is interesting is to look at its title. If by reading the title you do not think that the article is interesting, you should either move on to another article or do something else.5 In the rare event that you cannot find enough information in the title of a report to decide whether or not it is interesting, you are likely to find such information in the first portion of the abstract or in the introduction of the report. After reading the title of the article, if it seems interesting, you might feel tempted to jump to the conclusions in the abstract. This may occur: because of irresistible curiosity to know the bottom line of the article; because your time is so limited that reading the title and parts of the abstract is all that you can do; or because you do not want to know anything else, even if you have enough time to read the whole article. I hope that, if you have read any of the previous chapters of this book (or any of the series on how to use the medical literature that I mentioned above), you understand that the information in the title and the abstract could give you a misleading message. You should use the information in an abstract just as an additional source of information to determine if the trial is interesting to you, unless you are reading journals containing only structured abstracts of high quality studies published elsewhere (see Chapter 7). You should resist the temptation to use only the information provided by the abstract of an original study to make decisions about patient care. Are the trial results likely to be unbiased? It should take you approximately 3-5 minutes to assess the likelihood of bias in a trial report using the methods described above. With experience it could take you less than one minute, particularly if the authors have included methodological information in the title and the abstract. For example, if the title of the trial on therapeutic touch was The use of therapeutic touch for the treatment of malignant melanoma: a randomised double-blind trial you could not only decide whether the article is interesting, but you could also know immediately that the article describes an RCT and you could give it 2 points for being described as randomised and double-blind. Authors of RCT reports can help you find the information you need easily, if they follow simple approaches to make the titles of their reports as informative as possible. For instance, you will have no problem finding the information you need if the authors of the report have followed an approach that has been used extensively by journals such as ACP Journal Club and Evidence-Based Medicine, two journals that have been designed to help readers access high quality information efficiently (see Chapter 7). Using this approach, efforts are made to create informative titles that tell you something not only about the topic addressed by the trial, but also about its design and results. For instance, a more informative title for the hypothetical trial on therapeutic touch for the treatment of melanoma could be Therapeutic touch as a supplement to chemotherapy can increase survival in patients with metastatic melanoma: a randomised double-blind trial. The abstracts of RCT reports should ideally be structured, including a systematic disclosure of the objective, research design, clinical setting, participants, interventions, main outcome measures, results, and conclusions.24 Ideally, an abstract should contain enough information to allow you to judge how scientifically sound the trial is likely to be and how relevant its results may be to your immediate needs. If the abstract is informative enough, the information it contains should be sufficient to allow you to decide whether you should read more of the article or look at another one. As I emphasised earlier, regardless of how informative an abstract is, you should resist the temptation to use only the information provided there to make decisions about patient care. If, based on the information in the title and abstract, you think that the trial is neither scientifically sound nor relevant to you, then you should stop reading it and, if appropriate, move to another report. On many occasions you may think that the trial is not scientifically sound, but it is very relevant to you. In these cases, the decision as to whether to read the whole report or not should depend on the amount of additional literature available on the same topic. If you are aware of other trials addressing the same issue, then you could stop reading the report you just found. If you do not know of any other trial, however, you may want to read the whole report, very carefully, and make efforts to extract as much usable information as possible. On most occasions, such unique trials should be regarded as generators of hypotheses that you, or others, could test under more rigorous conditions. If, based on the information in the title and abstract, you think that the trial is likely to be scientifically sound and relevant, you could decide to read the whole article from beginning to end, or to read specific components of the report in a systematic manner not only to confirm whether the trial is as scientifically sound and interesting as the title and abstract suggest, but also to determine whether you could use the results and whether the results are important enough for you to remember. How can you determine if you would be able to use the results of a trial? As I have mentioned several times throughout the book, the research question is one of the most important components of a trial and its report. The research question is, however, frequently overlooked and underestimated by authors, peer-reviewers, and journal editors. Under ideal circumstances, the report should include a clearly identified research question, which is formulated in simple terms and includes information on the broad characteristics of the participants (that is, male adults over 65 years of age), the condition (that is, metastatic melanoma), the setting (that is, a tertiary level cancer centre), the interventions (that is, chemotherapy alone versus chemotherapy plus therapeutic touch), and the outcomes (that is, disease-free survival, quality of life).26 In our example, the research question could be formulated like this: What is the effect of therapeutic touch as a supplement to chemotherapy compared with surgery alone on the survival rate at 5 years of adult patients with metastatic melanoma attending a tertiary level cancer centre? As I said before, you will not find clearly described research questions in most of the reports you read. Not finding clearly described research questions should be one of the earliest signs of concern about the report you are reading. If you do not find a clear research question, but still think that the trial could be important to you, I would encourage you to try to find as much information as possible on the individual elements of the research question in the Abstract, Introduction and Methods section of the report. Once you have a better idea of the question or questions that the trial tried to answer, you should look for information on how the trial was executed to establish whether its results can be used by you. Does the report include enough information on the execution of the study?By looking for information on how the trial was executed, you will be able to judge how well it was executed and whether you could use its results. To judge the execution of a trial, you should answer the following questions.
Does the report include enough information on the results of the trial?
Once you address the previous issues and determine whether you could use the results of the trial, you should try to answer the following questions. Is the trial important enough for you to remember and use? Should you base your decisions on the results of a single trial? In the next chapter, I introduce you to different ways in which the information from a single trial can be integrated with information from other trials. References 1. Begg C, Cho M, Eastwood S, Horton R, Moher D, Olkin I, Pitkin R, Rennie D, Schulz KF, Simel D, Stroup D. Improving the quality of reporting of randomized controlled trials—The CONSORT Statement. JAMA 1996;276:7-9. 2. Altman DG. Better reporting of randomised controlled trials: the CONSORT statement. BMJ 1996;313:570-1. 3. Crombie IK. The pocket guide to critical appraisal. London: BMJ Publishing Group, 1996. 4. Greenhalgh T. How to read a paper: The basics of evidence based medicine. London: BMJ Publishing Group, 1996. 5. Department of Clinical Epidemiology and Biostatistics, McMaster University. How to read clinical journals: I. Why to read them and how to start reading them critically. Can Med Assoc J 1981;124:555-8. 6. Department of Clinical Epidemiology and Biostatistics, McMaster University. How to read clinical journals: II. To learn about a diagnostic test. Can Med Assoc J 1981;124:703-10. 7. Department of Clinical Epidemiology and Biostatistics, McMaster University. How to read clinical journals: III. To learn about the clinical course and prognosis of disease. Can Med Assoc J 1981;124:869-79. 8. Department of Clinical Epidemiology and Biostatistics, McMaster University. How to read clinical journals: IV. To determine the etiology or causation of disease. Can Med Assoc J 1981;124:985-90. 9. Department of Clinical Epidemiology and Biostatistics, McMaster University. How to read clinical journals: V. To distinguish useful from useless or even harmful therapy. Can Med Assoc J 1981;124:1156-62. 10. Department of Clinical Epidemiology and Biostatistics, McMaster University. How to read clinical journals: VI. To learn about the quality of clinical care. Can Med Assoc J 1984;130:377-81. 11. Guyatt GH, Sackett DL, 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. A. Are the results of the study valid? JAMA 1993;270:2598-601. 12. Guyatt GH, Sackett DL, 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. B. What were the results and will they help me in caring for my patients? JAMA 1994;271:59-63. 13.Guyatt G, Jaeschke R, Heddle N, Cook D, Shannon H, Walter S. Basic statistics for clinicians: 1. Hypothesis testing. Can Med Assoc J 1995;152:27-32. 14. Guyatt G, Jaeschke R, Heddle N, Cook D, Shannon H, Walter S. Basic statistics for clinicians: 2. Interpreting study results: confidence intervals. Can Med Assoc J 1995;152:169-73. 15. Guyatt G, Walter S, Shannon H, Cook D, Jaeschke R, Heddle N. Basic statistics for clinicians: 4. Correlation and regression. Can Med Assoc J 1995;152:497-504. 16. Jaeschke R, Guyatt G, Shannon H, Walter S, Cook D, Heddle N. Basic statistics for clinicians: 3. Assessing the effects of treatment: measures of association. Can Med Assoc J 1995;152:351-7. 17. Jadad AR, Moore RA, Carroll D, Jenkinson C, Reynolds JM, Gavaghan DJ, McQuay DM. Assessing the quality of reports on randomized clinical trials: Is blinding necessary? Controlled Clin Trials 1996;17:1-12. 18. Moher D, Jones A, Cook DJ, Jadad AR, Moher M, Tugwell P, Klassen TP. Does the poor quality of reports of randomized trials exaggerate estimates of intervention effectiveness reported in meta-analysis? In press, Lancet. 19. Schulz KF, Chalmers I, Hayes RJ, Altman DG. Empirical evidence of bias: dimensions of methodological quality associated with estimates of treatment effect in controlled clinical trials. JAMA 1995;273:408-12. 20. Cho MK, Bero LA. The quality of drug studies published in symposium proceedings. Ann Intern Med 1996;124:485-9. 21. Gotszche PC. Methodology and overt and hidden bias in reports of 196 double-blind trials of nonsteroidal antiinflammatory drugs in rheumatoid arthritis. Controlled Clin Trials 1989;10:31-56. 22. Moher D, Jadad AR, Nichol G, Penman M, Tugwell P, Walsh S. Assessing the quality of randomized controlled trials: an annotated bibliography of scales and checklists. Controlled Clin Trials 1995;16:62-73. 23. Jadad AR, Cook DJ, Jones AL, Klassen TP, Tugwell P, Moher M, Moher D. The quality of randomised controlled trials included in meta-analyses and systematic reviews: how often and how is it assessed? Published as: Abstract presented at the 4th Cochrane Colloquium, Adelaide, Australia, October 1996. In Review at Br Med J. 24. Haynes RB, Mulrow CD, Huth EJ, Altman DG, Gardner MJ. More informative abstracts revisited. Ann Intern Med 1990;113:69-76. 25. Bailey KR. Generalizing the results of randomized clinical trials. Controlled Clin Trials 1994;15:15-23. 26. Richardson W, Wilson M, Nishikawa J, Hayward RSA. The well-built clinical question: a key to evidence-based decisions. ACP J Club 1995;123:12-13. 27. Donner A, Brown KS, Brasher P. A methodological review of non-therapeutic intervention trials employing cluster randomization, 1979-1989. Int J Epidemiol 1990;19:795-800. 28. Altman DG. Comparability of randomized groups. Statistician 1985;34:125-36. 29. Evans M, Pollock AV. Trials on trial: a review of trials of antibiotic prophylaxis. Arch Surg 1984;119:109-13. 30. Gardner MJ, Bond J. An exploratory study of statistical assessment of papers published in the British Medical Journal. JAMA 1990;263:1355-7. 40. Altman DG. Practical statistics for medical research. London: Chapman & Hall, 1991. 41. Streiner DL, Norman GR. PDQ epidemiology, 2nd edn. St Louis: CV Mosby, 1996. 42. Oxman AD, Guyatt GH. A consumer's guide to subgroup analysis. Ann Intern Med 1992;116:78-84.
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Home | Contents | Foreword | Introduction | Acknowledgments | How to order © BMJ Books 1998. BMJ Books is an imprint of the BMJ Publishing Group. First published in 1998 by BMJ Books, BMA House, Tavistock Square, London WC1H 9JR. A catalogue record for this book is available from the British Library. ISBN 0-7279-1208-9 |