Conclusion: Because there was insufficient evidence on aquatic exercise due to poor methodological and reporting quality and heterogeneity of nRCTs, we were unable to offer any conclusions about the effects of this intervention. However, we were able to identify problems with current nRCTs of aquatic exercise, and propose a strategy of strengthening study quality, stressing the importance of study feasibility as a future research agenda objective.
Keywords: aquatic exercise; nonrandomized controlled trials; systematic review. Future interventional studies need to enhance methodological rigor using clearly defined outcome measures and standardized reporting of findings.
Abstract The purpose of this systematic review was to critically review and synthesize current evidence and the methodological quality of nonpharmacological infection-prevention interventions in long-term care LTC facilities for older adults. EFT produced large treatment effects whether delivered in group or individual format, and participants maintained their gains over time. This meta-analysis extends the existing literature through facilitation of a better understanding of the variability and clinical significance of depression improvement subsequent to EFT treatment.
Keywords: PTSD; depression; meta-analysis. The characteristics of included articles are shown in Table 2 and Table 3. We identified 8 systematic reviews [ 14 , 17 - 20 , 33 , 34 , 38 ] and 34 non-systematic reviews including editorials, comments, or letters.
The articles containing concepts relevant to our research question were published between and The systematic reviews covered 4 of 16 distinct clinical field categories with 5 of 8 reviews reporting on surgery and with 1 review reporting on acupuncture, cardiology, and various clinical fields, respectively Table 2. The non-systematic reviews covered 15 of 16 categories with 12 reporting on various topics, 4 reporting on surgery, no report on acupuncture, and 1 to 2 reporting on each of the rest of clinical entities.
Type of review. Non-systematic review rest of 34 papers : narrative review or editorial or comment or letter. Type of design. RCT: Randomized controlled trial; NRCT: Nonrandomized controlled trial: prospective comparative trial with allocation of patients by physician; Cohor: Prospective or retrospective observational study without allocation of patients by physician, start is intervention; CCS: Case-control study: retrospective study, start is events; Regist: Registry of data from patients with particular diseases or interventions; Admin: Administrative databases such as data from health care providers; Survey: Survey or audit or postmarketing analysis; Cases: Single case or case series.
Of the 15 methodological topics relevant for the integration of various study designs in systematic reviews, 5 topics were frequently reported by more than 10 articles Table 3. The rest were addressed by 1 article or up to 6 articles. Validity was reported by 30 reviews systematic 3, non-systematic 27 , applicability by 21 reviews systematic 6, non-systematic 15 , confounding by 21 reviews systematic 2, non-systematic 19 , adverse events by 18 reviews systematic 4, non-systematic 14 , and long-term follow up by 15 reviews systematic 4, non-systematic Systematic reviews reported 13 categories leaving pathogenesis and rare diseases out.
Non-systematic reviews reported 12 categories and did not refer to case load, specialisation, and survival. Outcomes addressed. We qualitatively summarized the key messages of the 42 included methods studies based on the extraction of major statements Table S2. Thus the majority of identified reviews supported the view that nonrandomized studies are important and should be an integral part of assessing health care interventions.
Only a minority of reviews regarded RCTs as the sole means of finding reliable answers to clinical research questions. Most papers acknowledged the advantages and the disadvantages of RCTs and nonrandomized studies with regard to specific methodologic topics or specific clinical outcomes. Some papers addressed the problem that RCTs are not possible for assessing certain questions and that case reports may have a considerable impact on safety issues.
We identified 49 studies, 18 trials and 31systematic reviews that compared the effect measures found in randomized controlled trials with those in nonrandomized controlled trials Table 4. Of these 49 studies, 39 reported about the same or similar intervention in both study designs and 10 studies that included different interventions in the analyses.
We identified and summarized qualitative evidence sufficient enough to guide finding and integrating the right research design for answering various clinical questions within the conduct of systematic reviews of health care interventions.
It is obvious that intended effects of interventions such as the physician-reported outcomes of prevention of death and healing or improving of disease in ideal settings with financially affordable follow up and with ample number of available participants are best investigated in well planned RCTs. There is no equal or better alternative study design. The results may or may not be applicable to the general population. Many people with particular characteristics such as younger or older age, gender, pregnancy, or comorbidity may have been excluded and may have experienced opposing effects or an unfavorable and unwanted balance of benefit and harm.
Pediatricians may seek information on drugs from observational studies if data on the treatment of children from RCTs are not available. Unintended, severe adverse events require long-term observation including postmarketing analysis, administrative databases, and case reports to identify harmful drugs that have to be withdrawn from the market. The types of different study design that need to be included in a systematic review depend on the nature of the clinical questions that the review addresses.
Oxman and collaborators assessed the effects of randomisation and concealment of allocation on the results of healthcare studies and reported their results in three papers within the time period from to [ 53 - 55 ].
The authors concluded that "the results of randomised and non-randomised studies — sometimes — differed". In many cases the results did not differ. The authors argued "that it is not generally possible to predict the magnitude, or even the direction, of possible selection biases and consequent distortions of treatment effects from studies with non-random allocation or controlled trials with inadequate or unclear allocation concealment".
We believe that trials with random allocation and adequate allocation concealment may show contradictory results. We also believe that it is not possible to foresee the magnitude or the direction of bias in those adequately randomized trials with absolute certainty [ 56 ].
Nevertheless, the authors stated that "randomized controlled trials are a safeguard against biased estimates of treatment effects". Various design prerequisites and adjustment procedures in nonrandomized controlled trials can minimize bias and confounding, however, it is not kown for certain in a particular trial whether the results reflect the reality or whether they are distorted.
The same principle holds true for trials with adequate randomization and concealment of allocation. Even if the risk of a false estimate determined in a series of trials would be lower than in trials with inadequate randomization and concealment of allocation the fact is that the result of the primary outcome measure in a single specific trial cannot be regarded as an absolute and certain proof regardless of the p-values or confidence intervals. Ioannidis concluded that, quote: "Controversies are most common with highly cited nonrandomized studies, but even the most highly cited randomized trials may be challenged and refuted over time, especially small ones" [ 57 ].
Our assessment adds to the existing work done by Oxman group and the Ioannidis group that the effect did not differ considerably between the randomized and the nonrandomized designs in more than half of the studies. The general postulate or dogma of the RCT as a safeguard against biased estimates of treatment effects may create deceptive promises and may give researchers a false sense of security. We infer from our findings just the same as Shrier has expressed before, quote: " According to the Cochrane handbook, the Cochrane Collaboration focuses particularly on systematic reviews of RCTs and considers inclusion of nonrandomized studies mainly if RCTs are lacking.
We see a vast number of clinical research questions that are not investigated by RCTs. There may be many reasons, for example, patients' and physicians' preferences that prevent the accumulation of true randomized study data. Our results suggest that the Cochrane Collaboration might be advised to consider more reasons for including nonrandomized studies on the condition of a rigorous risk of bias assessment and confinement to specific interventions and outcomes.
In general, a high risk of bias is inherent in all nonrandomized studies. Certain study characteristics such as prospective design, concurrent control group, adjustment of results with respect to different baseline values, and confounder control can limit additional bias.
For example, Ioannidis [ 58 ] reported that discrepancies between RCT and nonrandomized studies were less common when only nonrandomized studies with a prospective design were considered. The Cochrane Collaboration offers a guide for inclusion of nonrandomized studies [ 59 ] and it has developed a tool for assessing the risk of bias in both RCT and controlled nonrandomized studies[ 60 ].
The risk of presenting uncertain results without knowing for sure the direction and magnitude of the effect holds true for both nonrandomized and randomized controlled trials, though, the risk of bias and confounding is probably higher in the nonrandomized ones. Qualitative summary of key messages. The University of Cologne provided the fulltexts. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. National Center for Biotechnology Information , U.
PLoS One. Published online Dec Matthias Briel, Editor. Author information Article notes Copyright and License information Disclaimer. Competing Interests: No authors have any competing interests. Received Jul 2; Accepted Nov This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are properly credited.
This article has been cited by other articles in PMC. Table S2: Qualitative summary of key messages. Other abbreviations.
Ref: reference. Abstract Background A systematic review may evaluate different aspects of a health care intervention. Methods and Findings We searched PubMed, the Cochrane Database of Systematic Reviews, and the Cochrane Methodology Register on 31 March and identified 42 articles that reported on the integration of single or multiple study designs in systematic reviews. Conclusions Different study designs addressing the same question yielded varying results, with differences in about half of all examples.
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