PHYS THER
Vol. 88, No. 9, September 2008, pp. 1068-1077
DOI: 10.2522/ptj.20080002
A Description of the Trials, Reviews, and Practice Guidelines Indexed in the PEDro Database
Christopher G Maher,
Anne M Moseley,
Cathie Sherrington,
Mark R Elkins and
Robert D Herbert
CG Maher, PhD, is Director, Musculoskeletal Division, The George Institute for International Health, PO Box M201, Missenden Road, Sydney, NSW 2050, Australia, and Professor, Faculty of Medicine, University of Sydney, Lidcombe, NSW, Australia
AM Moseley, PhD, is Senior Research Fellow, The George Institute for International Health and Faculty of Medicine, University of Sydney
C Sherrington, PhD, is Senior Research Fellow, The George Institute for International Health and Faculty of Medicine, University of Sydney
MR Elkins, PhD, is Research Physiotherapist, Royal Prince Alfred Hospital, Sydney
RD Herbert, PhD, is Associate Professor, The George Institute for International Health and Faculty of Medicine, University of Sydney
Address all correspondence and reprint requests to Dr Maher at: cmaher{at}george.org.au
Submitted January 2, 2008;
Accepted May 2, 2008
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Abstract
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This perspective provides an overview of the randomized controlled trials, systematic reviews, and evidence-based clinical practice guidelines in physical therapy. Data from the Physiotherapy Evidence Database (PEDro) are used to describe key events in the history of physical therapy research and the growth of evidence of effects of interventions used in the various subdisciplines of physical therapy. The 11,494 records that were identified reveal a rich history of physical therapy research dating back to the first trial in 1929. Most of the randomized controlled trials, systematic reviews, and evidence-based clinical practice guidelines in physical therapy have been published since the year 2000. This rapid growth presents a challenge for physical therapists who want to keep up to date in clinical practice.
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Introduction
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Several physical therapy associations1–3 now explicitly advocate an approach to practice that is informed by scientific evidence. This approach, however, presents a number of challenges to practitioners. One key challenge is keeping up to date with the evidence underpinning physical therapist practice. This challenge exists because there has been a rapid expansion in physical therapy research in the past 2 decades, much of which is not indexed in general databases such as MEDLINE.
Our interest is in the evidence of the effects of therapy provided by high-quality randomized controlled trials (RCTs), systematic reviews of such trials, and evidence-based clinical practice guidelines. We have chosen to describe key events in the history of physical therapy clinical trials, RCTs, reviews, and guidelines and provide an overview of the quantity and quality of this research. We chose to describe this information because we agree with proponents of evidence-based practice4 that these research designs provide the most reliable evidence for the effects of therapy; however, we are aware that alternate views exist.5 We also acknowledge that other types of evidence (eg, that provided by qualitative research and studies of diagnosis and prognosis) also are of value in clinical decision making. Consideration of these types of studies, however, is beyond the scope of this perspective. We hope that other authors will take up the challenge and write a similar perspective covering these other types of evidence.
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Methods
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With the help of several organizations and many volunteers, we have produced a Web-based database of RCTs, systematic reviews, and evidence-based clinical practice guidelines in physical therapy (Physiotherapy Evidence Database or PEDro) (http://www.pedro.fhs.usyd.edu.au).6 This article describes that evidence.
Randomized controlled trials in the database are rated for methodological quality using the PEDro scale,7–9 a scale modified from the Delphi list.10 The PEDro scale is an 11-item scale designed for rating methodological quality of RCTs (the scale items and operational definitions for each scale item are given in the Appendix). Each satisfied item (except for item 1, which, unlike other scale items, pertains to external validity) contributes one point to the total PEDro score (range=0–10 points).
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The Beginning of Physical Therapy Research
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One view we commonly encounter is that research is a recent endeavor in physical therapy. This is not true. The first RCTs in physical therapy evaluated electrotherapy. Colebrook's trial11 was published in 1929 (Fig. 1) and Doull and colleagues’ RCT12 was published in 1931. Both trials predate the 1934 Medical Research Council trial13 that evaluated the treatment of pneumonia and is commonly (although incorrectly) believed to be the first modern clinical trial.14 In contrast to the Medical Research Council trial, which assigned cases alternately to a treatment group or a control group, the 2 early physical therapy trials used true random allocation. Evaluation of various forms of electrotherapy continues to be a major part of physical therapy research. At present, there are 1,421 RCTs of electrotherapy, most evaluating the use of electrotherapy for pain relief.
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Figure 1. First report of a randomized trial in physical therapy. Reprinted with permission of the Medical Research Council from: Colebrook D. Irradiation and health, A: ultra-violet irradiation of school children. Medical Research Council. Special Report Series. 1929;131:1–47.
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Growth in Physical Therapy Evidence
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By 1960, there were 15 RCTs, with at least 1 RCT in each of 3 core areas of physical therapist practice: neurology, musculoskeletal, and cardiopulmonary. Over the next 4 decades, there was an exponential increase in RCTs: there were 86 RCTs by 1970, 441 by 1980, 1,925 by 1990, and 5,301 by 2000 (Fig. 2). With such a growth in research evidence, it became important to conduct systematic reviews in order to appraise and summarize the available RCT evidence and to produce clinical practice guidelines.
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Figure 2. Cumulative number of randomized controlled trials, systematic reviews, and evidence-based clinical practice guidelines in physical therapy, by year, at the time of data analysis (September 3, 2007).
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The first systematic review in physical therapy was published in 1975 by Kolind-Sorensen.15 By 1991, there were 39 systematic reviews, with at least 1 review in each of the core areas of physical therapist practice. The first evidence-based clinical practice guideline relevant to physical therapy, the report of the Quebec Task Force on Spinal Disorders,16 was published in 1987, and by 1995 there were 19 guidelines, with at least 1 guideline in each of the 3 core areas of physical therapist practice. Compared with the growth in RCTs, the growth in the number of systematic reviews and guidelines has been more modest. At the time of data analysis for this article (September 3, 2007), there were 11,494 records indexed in the PEDro database: 9,475 RCTs, 1,541 systematic reviews, and 478 evidence-based clinical practice guidelines.*
This rapid growth in research has enormous implications for physical therapist education and practice. As an example, a physical therapist who graduated in 1980 could only have been exposed to less than 5% of today's evidence (RCTs, systematic reviews, and clinical practice guidelines) during his or her training. Even someone who graduated in 2000 could only have been exposed to about 50% of today's evidence during his or her training. In our opinion, this problem is likely to be even more acute for medical practitioners, and it is likely that most medical practitioners’ initial training would not have provided them with an adequate understanding of the current evidence regarding the effects of physical therapy treatments. This is particularly a concern in regions where physical therapists do not have primary contact status and instead provide treatment at the direction of the referring medical practitioner. These referrals may not be based on the best available evidence on the effects of physical therapy treatments.
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Quality of Evidence
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As mentioned above, a scale is used to rate the methodological quality of RCTs in the PEDro database. Items on this scale include those reflecting the allocation process (randomization method, use of concealment), blinding or masking (patients, therapists, outcome assessors); follow-up, and analysis (use of intent-to-treat analysis, reporting of analysis). The first physical therapy trial to use random allocation was Colebrook's 1929 trial,11 with concealed allocation first used in Doull and colleagues’ RCT12 in 1931. Palmer and Sellick's 1953 RCT17 was the first physical therapy trial to blind the assessor, Cezeaux and colleagues’ 1967 RCT18 the first to blind the patient, and Vyas and colleagues’ 1971 RCT19 was the first to blind the therapist. In Wilson's 1972 RCT20 evaluating pulsed shortwave diathermy, the researchers managed to blind patient, therapist, and assessor. To put this in historical perspective, blinding of assessors and patients had been a feature of experiments in the early 19th century, and blinding of assessors, patients, and therapists was achieved in evaluations of homeopathic remedies conducted in the late 19th century.21 The challenge for physical therapy RCTs was that it was difficult to develop placebos for the physical treatments of the time. However, patient and therapist blinding became possible with the development of electrotherapy treatments such as pulsed ultrasound and shortwave diathermy, which may not provide any sensation to the patient and can be configured so that the operator does not know whether any output is being produced.
Figure 3 shows the proportion of RCTs that satisfied each item of the PEDro scale, and Figure 4 shows the frequency distribution of the total PEDro score (range=0–10). These figures show that the available RCTs vary greatly in methodological quality and, therefore, in their ability to provide valid and interpretable results. Figure 5 shows how the methodological quality of physical therapy RCTs has improved over time. This welcome trend compounds the problems faced by more experienced clinicians: not only were they only exposed to a smaller subset of the evidence during their training, but the evidence they were exposed to is more likely to provide biased estimates of treatment effectiveness.
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Figure 3. Percentage of the randomized controlled trials that satisfied each item of the PEDro scale (based on 9,475 trials archived at the time of data analysis [September 3, 2007]).
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Figure 4. Frequency distribution of the total PEDro score for the 9,475 randomized controlled trials archived at the time of data analysis (September 3, 2007).
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Figure 5. Mean and standard deviation of the total PEDro score of randomized controlled trials in physical therapy for time epochs since 1929. The number of trials published during each epoch is indicated at the end of each bar.
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Coverage of Evidence
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The dates of publication of the first RCT, review, and guideline in 9 subdisciplines of physical therapy are shown in the time line in the Table.11,12,15–19,22–27 It is noteworthy that the total amount of evidence (Fig. 6) and growth in evidence in each of the subdisciplines of physical therapy (Fig. 7) vary substantially. Interestingly, some high-profile areas of physical therapist practice, such as sports physical therapy and ergonomics, have relatively little discipline-specific evidence available to guide practice. Another feature that is of interest is the relative decrease in pediatric research: although this subdiscipline in the 1970s was ranked third in terms of output, it has now fallen to seventh.
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Figure 6. Number of randomized controlled trials (RCTs), systematic reviews (SRs), and evidence-based clinical practice guidelines (CPGs) in each area of physical therapy (columns do not tally with the total number of records in PEDro because trials, reviews, and guidelines can be coded for up to 3 areas of physical therapy).
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Figure 7. Growth of evidence in each specialty area of physical therapy in the past 4 decades (top to bottom: 1970s, 1980s, 1990s, 2000s). Figure shows number of PEDro records published in each decade.
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Some health conditions have been extensively studied. As an illustration, there are 1,037 records dealing with lumbar spine/sacroiliac joint/pelvis treatment and 997 records dealing with treatment of the knee or lower leg. There also are some surprises in terms of the relative amount of evidence on treatment for particular health problems. For example, some physical therapists may not be aware that there is more evidence on physical therapy treatment of incontinence (173 records) than there is for treatments for tennis elbow (56 records) or thoracic spine pain (61 records).
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Where Is the Evidence Published?
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The early physical therapy trials were published in general medical journals, and it was not until 1967 that the first RCT was published in a physical therapy journal.22 The 11,494 records that we have identified were published in 1,484 different journals in 30 languages, with publications dating from 1929 to 2007. This means that the traditional strategy of visiting a library and scanning the readily available general medical and physical therapy journals potentially misses a lot of research. As an illustration, only 3% of the records in PEDro were published in the general medical journals New England Journal of Medicine, Lancet, JAMA, Annals of Internal Medicine, BMJ, and CMAJ, and about 3% of records were published in the physical therapy journals Physical Therapy, Physiotherapy, Australian Journal of Physiotherapy, and Physiotherapy Canada. The only feasible way to find relevant evidence from this enormous volume of physical therapy research is to use electronic databases such as PubMed, Hooked on Evidence, or PEDro.
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Limitations of the Perspective
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We acknowledge that PEDro is only one database that archives physical therapy evidence and that other databases, such as Hooked on Evidence, might provide a different set of records and quality ratings. An analysis of the records from both databases might provide interesting findings.
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Conclusions
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There has been an exponential increase in physical therapy research since the first RCT in 1929. With about 11,500 trials, reviews, and guidelines published to date, much has been revealed about the effects of physical therapy treatments. This evidence can be used by physical therapists and their patients when making decisions about physical therapy intervention.
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Appendix.
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Appendix. PEDro Scale Criteria, Scale Items, and Operational Definitionsa
aThe PEDro scale items and operational definitions were developed by Directors of the Centre for Evidence-Based Physiotherapy. The Centre encourages use of the scale and does not require written permission prior to use. SIJ=sacroiliac joint.
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Footnotes
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Each of the authors met the 3 International Committee of Medical Journal Editors authorship criteria. All authors provided concept/idea/project design, writing, data collection and analysis, project management, fund procurement, facilities/equipment, institutional liaisons, and consultation (including review of manuscript before submission).
The PEDro project has received in-kind and financial support from individual physical therapists, physical therapy associations (including the American Physical Therapy Association), and government/health/education agencies (including the Motor Accidents Authority of New South Wales). A full list of supporters is available at this site: http://www.pedro.fhs.usyd.edu.au/supporters.html. Dr Maher's, Dr Herbert's, and Dr Sherrington's research fellowships are funded by Australia's National Health and Medical Research Council. Dr Moseley's salary is funded by a research grant from the Motor Accidents Authority of New South Wales.
* In May 2008, when the article was being prepared for publication, there were 12,553 records in PEDro. 
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Copyright © 2008 by the American Physical Therapy Association.
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Introduction
Methods