Reinhard Wentz

Increasing response rates to postal questionnaires: systematic review

Abstract Objective: To identify methods to increase response to postal questionnaires. Design: Systematic review of randomised controlled trials of any method to influence response to postal questionnaires. Studies reviewed: 292 randomised controlled trials including 258 315 participants Intervention reviewed: 75 strategies for influencing response to postal questionnaires. Main outcome measure: The proportion of completed or partially completed questionnaires returned. Results: The odds of response were more than doubled when a monetary incentive was used (odds ratio 2.02; 95% confidence interval 1.79 to 2.27) and almost doubled when incentives were not conditional on response (1.71; 1.29 to 2.26). Response was more likely when short questionnaires were used (1.86; 1.55 to 2.24). Personalised questionnaires and letters increased response (1.16; 1.06 to 1.28), as did the use of coloured ink (1.39; 1.16 to 1.67). The odds of response were more than doubled when the questionnaires were sent by recorded delivery (2.21; 1.51 to 3.25) and increased when stamped return envelopes were used (1.26; 1.13 to 1.41) and questionnaires were sent by first class post (1.12; 1.02 to 1.23). Contacting participants before sending questionnaires increased response (1.54; 1.24 to 1.92), as did follow up contact (1.44; 1.22 to 1.70) and providing non-respondents with a second copy of the questionnaire (1.41; 1.02 to 1.94). Questionnaires designed to be of more interest to participants were more likely to be returned (2.44; 1.99 to 3.01), but questionnaires containing questions of a sensitive nature were less likely to be returned (0.92; 0.87 to 0.98). Questionnaires originating from universities were more likely to be returned than were questionnaires from other sources, such as commercial organisations (1.31; 1.11 to 1.54). Conclusions: Health researchers using postal questionnaires can improve the quality of their research by using the strategies shown to be effective in this systematic review. What is already known on this topic Postal questionnaires are widely used in the collection of data in epidemiological studies and health research Non-response to postal questionnaires reduces the effective sample size and can introduce bias What this study adds This systematic review includes more randomised controlled trials than any previously published review or meta-analysis no questionnaire response The review has identified effective ways to increase response to postal questionnaires The review will be updated regularly in the Cochrane Library

Systematic review of prognostic models in traumatic brain injury

BackgroundTraumatic brain injury (TBI) is a leading cause of death and disability world-wide. The ability to accurately predict patient outcome after TBI has an important role in clinical practice and research. Prognostic models are statistical models that combine two or more items of patient data to predict clinical outcome. They may improve predictions in TBI patients. Multiple prognostic models for TBI have accumulated for decades but none of them is widely used in clinical practice. The objective of this systematic review is to critically assess existing prognostic models for TBIMethodsStudies that combine at least two variables to predict any outcome in patients with TBI were searched in PUBMED and EMBASE. Two reviewers independently examined titles, abstracts and assessed whether each met the pre-defined inclusion criteria.ResultsA total of 53 reports including 102 models were identified. Almost half (47%) were derived from adult patients. Three quarters of the models included less than 500 patients. Most of the models (93%) were from high income countries populations. Logistic regression was the most common analytical strategy to derived models (47%). In relation to the quality of the derivation models (n:66), only 15% reported less than 10% pf loss to follow-up, 68% did not justify the rationale to include the predictors, 11% conducted an external validation and only 19% of the logistic models presented the results in a clinically user-friendly wayConclusionPrognostic models are frequently published but they are developed from small samples of patients, their methodological quality is poor and they are rarely validated on external populations. Furthermore, they are not clinically practical as they are not presented to physicians in a user-friendly way. Finally because only a few are developed using populations from low and middle income countries, where most of trauma occurs, the generalizability to these setting is limited.

Size and quality of randomised controlled trials in head injury: review of published studies

Abstract Objective: To assess whether trials in head injury are large enough to avoid moderate random errors and designed to avoid moderate biases. Design: All randomised controlled trials on the treatment and rehabilitation of patients with head injury published before December 1998 were surveyed. Trials were identified from electronic databases, by hand searching journals and conference proceedings, and by contacting researchers. Data were extracted on the number of participants, quality of concealment of allocation, use of blinding, loss to follow up, and types of participants, interventions, and outcome measures. Results: 279 reports were identified, containing information on 208 separate trials. The average number of participants per trial was 82, with no evidence of increasing size over time. The total number of randomised participants in the 203 trials in which size was reported was 16 613. No trials were large enough to detect reliably a 5% absolute reduction in the risk of death or disability, and only 4% were large enough to detect an absolute reduction of 10%. Concealment of allocation was adequate in 22 and inadequate or unclear in 25 of the 47 (23%) in which it was reported. Of 126 trials assessing disability, 111 reported the number of patients followed up, and average loss to follow up was 19%. Of trials measuring disability, 26 (21%) reported that outcome assessors were blinded. Conclusions: Randomised trials in head injury are too small and poorly designed to detect or refute reliably moderate but clinically important benefits or hazards of treatment. Limited funding for injury research and unfamiliarity with issues of consent may have been important obstacles.

Traffic calming for the prevention of road traffic injuries: systematic review and meta-analysis

Objective: To assess whether area-wide traffic calming schemes can reduce road crash related deaths and injuries. Design: Systematic review and meta-analysis. Data sources: Cochrane Injuries Group Specialised Register, Cochrane Central Register of Controlled Trials, Medline, EMBASE, Sociological Abstracts Science (and social science) citation index, National Technical Information service, Psychlit, Transport Research Information Service, International Road Research Documentation, and Transdoc, and web sites of road safety organisation were searched; experts were contacted, conference proceedings were handsearched, and relevant reference lists were checked. Inclusion criteria: Randomised controlled trials, and controlled before/after studies of area-wide traffic calming schemes designed to discourage and slow down through traffic on residential roads. Methods: Data were collected on road user deaths, injuries, and traffic crashes. For each study rate ratios were calculated, the ratio of event rates before and after intervention in the traffic calmed area divided by the corresponding ratio of event rates in the control area, which were pooled to give an overall estimate using a random effects model. Findings: Sixteen controlled before/after studies met our inclusion criteria. Eight studies reported the number of road user deaths: pooled rate ratio 0.63 (95% confidence interval (CI) 0.14 to 2.59). Sixteen studies reported the number of injuries (fatal and non-fatal): pooled rate ratio 0.89 (95% CI 0.80 to 1.00). All studies were in high income countries. Conclusion: Area-wide traffic calming in towns and cities has the potential to reduce road traffic injuries. However, further rigorous evaluations of this intervention are needed, especially in low and middle income countries.

Identifying controlled evaluation studies of road safety interventions: Searching for needles in a haystack

Problem: Worldwide, over one million people die and about 10 million people sustain permanent disabilities each year in road traffic crashes. It is a matter of urgency that effective strategies, especially from existing controlled trials (CTs), are identified for crash prevention programs. Methods: We used word frequency analysis to develop a search strategy of known sensitivity and positive predictive value (PPV) to identify reports of controlled evaluation studies of road safety interventions in the TRANSPORT database. Results: 23,554 records were searched and 319 (1.4%) records of controlled evaluation studies were identified by handsearching. We were unable to devise search strategies that combined acceptable sensitivity and PPV. Impact on industry: Efforts to improve the identification of CTs of road safety interventions are urgently required. This would involve the documentation of the study design in the title, abstract, and methods section of the research report. The study methodology should be carefully and consistently indexed in road safety databases, and editors can encourage appropriate indexing by insisting on the use of structured abstracts that give details of study methodology.

Car manufacturers and global road safety: a word frequency analysis of road safety documents

Objective: The World Bank believes that the car manufacturers can make a valuable contribution to road safety in poor countries and has established the Global Road Safety Partnership (GRSP) for this purpose. However, some commentators are sceptical. The authors examined road safety policy documents to assess the extent of any bias. Design: Word frequency analyses of road safety policy documents from the World Health Organization (WHO) and the GRSP. Main outcome measures: The relative occurrence of key road safety terms was quantified by calculating a word prevalence ratio with 95% confidence intervals. Terms for which there was a fourfold difference in prevalence between the documents were tabulated. Results: Compared to WHO’s World report on road traffic injury prevention, the GRSP road safety documents were substantially less likely to use the words speed, speed limits, child restraint, pedestrian, public transport, walking, and cycling, but substantially more likely to use the words school, campaign, driver training, and billboard. Conclusions: There are important differences in emphasis in road safety policy documents prepared by WHO and the GRSP. Vigilance is needed to ensure that the road safety interventions that the car industry supports are based on sound evidence of effectiveness.

The development of a register of randomized controlled trials in prehospital trauma care

Objectives. To establish a register of randomized controlled trials of interventions in the prehospital care of trauma patients. Methods. A systematic search was conducted for all randomized controlled trials of interventions in the prehospital care of trauma patients. The search included the Cochrane Controlled Trial Register, the Cochrane Injuries Group Specialised Register, Medline, EMBASE, the Cumulative Index to Nursing & Allied Health Literature (CINAHL), Science Citation Index, National Research Register, Dissertation Abstracts, and PubMed for the time period 1966–2000. There were no language restrictions. In addition, full-text hand searching of a range of relevant journals was done, and the authors of included trials were contacted. Results. The combined search strategy identified 16,037 potentially eligible records, of which 28 were reports of randomized controlled trials evaluating prehospital trauma care interventions. After excluding duplicate reports, there were 24 separate randomized controlled trials including 6,806 patients. The largest and smallest trials involved 1,309 and 30 trauma patients, respectively. Conclusions. This register will facilitate the conduct of systematic reviews of the effectiveness of interventions in prehospital trauma care. However, despite the extensive searching, very few randomized trials in this area were found. In view of the absence of evidence for the effectiveness of many of the interventions that are used in the prehospital care of trauma patients, further randomized controlled trials are required.

Pragmatic approach is effective in evidence based health care

EDITOR—We agree with Guyatt et al that providing evidence based answers to clinical questions requires intensive study and application if the process is seen in the context of a systematic review of the original literature.1 The main stumbling block remains the difficulty of constructing complex searches appropriate for a range of potential sources. We suggest that many typical clinical questions can be answered by using a …