Background: Poor response to questionnaires collecting outcome data in randomised controlled trials (RCTs) can affect the validity of trial results. The aim of this study within a trial (SWAT) was to evaluate the effectiveness of including a pen with a follow-up postal questionnaire on response rate. Methods: A two-armed RCT was embedded within SSHeW (Stopping Slips among Healthcare Workers), a trial of slip-resistant footwear to reduce slips in NHS staff.  Participants were randomised 1:1 to receive a pen or no pen with their follow-up questionnaire. The primary outcome was the proportion of participants who returned the questionnaire. Secondary outcomes were: time to response, completeness of response, and whether a postal reminder notice was required. Data were analysed using logistic regression, linear regression and Cox proportional hazards regression. Results: Overall, 1466 SSHEW trial participants were randomised into the SWAT. In total, 13 withdrew from the host trial before they were due to be sent their follow-up questionnaire, 728 participants received a pen with their questionnaire, and 725 did not receive a pen.  A questionnaire was returned from 67.7% of the pen group and 64.7% of the group who did not receive a pen. There was no significant difference in return rates between the two groups (OR 1.15, 95% CI 0.92 to 1.43, p=0.22), nor level of completeness of the questionnaires (AMD -0.01, 95% CI 0.06 to 0.05, p=0.77).  There was weak evidence of a reduction in the proportion of participants requiring a reminder and in time to response in the pen group. Conclusion: Inclusion of a pen with the follow-up postal questionnaire sent to participants in the SSHeW trial did not statistically significantly increase the response rate. These results add to the body of evidence around improving response rates in trials. Trial registration: ISRCTN 33051393 (for SSHEW). Registered on 14/03/2017.

IntroductionSlips, trips and falls are common causes of injuries in the workplace. It is estimated that in Great Britain, nearly 1 million days are taken off work due to these injuries. There is some evidence to suggest this accident burden could be reduced by the use of slip resistant footwear. This protocol describes a multicentre trial investigating the effectiveness and cost-effectiveness of slip resistant footwear to prevent slips in National Health Service (NHS) staff working in clinical, general or catering environments.Methods and analysisA two-arm, randomised controlled trial conducted within England, with 4400 NHS staff, aged 18 years and above, who adhere to a dress code policy and work in a clinical, catering or general hospital environment. Participants will be randomised 1:1 to the intervention or waiting list control group. The intervention group will be offered a pair of 5-star GRIP rated slip resistant footwear. The control group will be offered the footwear at the end of the trial. The primary outcome is the incidence rate of self-reported slips in the workplace over a 14-week period, as reported via weekly text messages. Secondary outcomes include: time to first slip/fall, proportion of participants who slip and fall over 14 weeks and incidence rate of falls resulting from and not resulting from a slip in the workplace over 14 weeks. An economic evaluation will assess cost-effectiveness, in terms of cost per quality-adjusted life year gained. A nested qualitative study will explore the acceptability of the footwear and compliance.Ethics and disseminationThis protocol received a favourable ethical opinion from the University of York, Department of Health Sciences Research Governance Committee. The trial results will be published in peer-reviewed journals and at conferences. A summary of the findings will be made available to participants.Trial registration number ISRCTN33051393; Pre results.

ObjectivesAssess the effectiveness of 5* GRIP-rated slip-resistant footwear in preventing slips in the workplace compared to usual footwear (control group).MethodsA multicentre, randomised controlled trial; 4553 National Health Service (NHS) staff were randomised 1:1 to the intervention group (provided with 5* GRIP-rated slip-resistant footwear) or the control group. The primary outcome of incidence rate of self-reported slips in the workplace over 14 weeks was analysed using a mixed-effects negative binomial model. Secondary outcome measures included incidence rate of falls from a slip, falls not from a slip, proportion of participants reporting a slip, fall or fracture and time to first slip and fall.Results6743 slips were reported: 2633 in the intervention group (mean 1.16 per participant, range 0 to 36) and 4110 in the control group (mean 1.80 per participant, range 0 to 83). There was a statistically significant reduction in slip rate in the intervention group relative to the control group (incidence rate ratio (IRR) 0.63, 95% CI 0.57 to 0.70, p<0.001). Statistically significant differences, in favour of the intervention group, were observed in falls from a slip (IRR 0.51, 95% CI 0.28 to 0.92, p=0.03), the proportion of participants who reported a slip (OR 0.58, 95% CI 0.50 to 0.66, p<0.001) or fall (OR 0.73, 95% CI 0.54 to 0.99, p=0.04) and time to first slip (HR 0.73, 95% CI 0.67 to 0.80, p<0.001).ConclusionsThe offer and provision of 5* GRIP-rated footwear reduced slips in NHS staff in the workplace.Trial registration numberISRCTN33051393.

Background In Great Britain, 100,000 injuries due to slips, trips and falls on the level (as opposed to falls from a height, e.g. a ladder) occur in the workplace each year. They are the most common cause of non-fatal injury in the workplace, accounting for 30% of all those injuries reported to the Health and Safety Executive. Nearly 1 million working days are lost because of slips, trips and falls each year. Objectives To assess the clinical effectiveness and cost-effectiveness of 5-star, GRIP-rated, slip-resistant footwear in preventing slips in the workplace compared with usual footwear. Design A two-arm, multicentre, randomised controlled trial with an economic evaluation and qualitative study. Setting Seven NHS trusts in England. Participants NHS staff aged ≥ 18 years, working at least 22.5 hours per week in clinical, general or catering areas who owned a mobile phone. Staff required to wear protective footwear were excluded. Interventions Intervention participants were offered 5-star, GRIP-rated, slip-resistant footwear. The waiting list control group were asked to wear their usual work shoes for the duration of the study and were offered the trial footwear at the end of their participation. Main outcome measures The primary outcome was the incidence rate of self-reported slips in the workplace over 14 weeks. Secondary outcomes included the incidence rate of falls either resulting from a slip or not resulting from a slip, proportion of participants reporting a slip, fall or fracture, time to first slip and fall, health-related quality of life and cost-effectiveness. Results A total of 4553 eligible NHS staff were randomised (2275 to the intervention arm and 2278 to the control arm). In total, 6743 slips were reported [2633 in the intervention group (mean 1.16 per participant, range 0–36 per participant) and 4110 in the control group (mean 1.80 per participant, range 0–83 per participant)]. There was a statistically significant reduction in the slip rate in the intervention group relative to the control group (incidence rate ratio 0.63, 95% confidence interval 0.57 to 0.70; p < 0.001). Statistically significant reductions were observed in falls from a slip (incidence rate ratio 0.51, 95% confidence interval 0.28 to 0.92; p = 0.03), the proportion of participants who reported a slip (odds ratio 0.58, 95% confidence interval 0.50 to 0.66; p < 0.001) or fall (odds ratio 0.73, 95% confidence interval 0.54 to 0.99; p = 0.04) and the time to first slip (hazard ratio 0.73, 95% confidence interval 0.67 to 0.80; p < 0.001). Half of the intervention participants wore the shoes all the time at work. Incremental cost per quality-adjusted life-year in the base case was £38,900 from the NHS perspective and –£60,400 (i.e. cost saving) from the societal perspective. Limitations This was an unblinded trial in which outcome data were participant self-reported, which may have led to inaccuracies in the reported slip data. Exposure to the trial footwear was lower than hoped. Conclusions The offer and provision of 5-star, GRIP-rated footwear reduced slips in the workplace, was acceptable to participants and could be cost-effective. Future work Replication of the study within other settings may be required to evaluate the clinical effectiveness and cost-effectiveness in other environments settings, such as catering and factories. Trial registration Current Controlled Trials ISRCTN33051393. Funding This project was funded by the National Institute for Health Research (NIHR) Public Health Research programme and will be published in full in Public Health Research; Vol. 9, No. 3. See the NIHR Public Journals Library website for further project information. The Health and Safety Executive provided some research costs.

ObjectiveTo assess the association of the quality of allocation concealment with heterogeneity in age, the P value of the primary outcome and statistical significance of the primary outcome.Study design and settingWe extracted data from articles published in four major medical journals in 2017 and 2018 that reported the results of randomized controlled trials. The outcome measures were the quality of allocation concealment used in the trial, the P value of the primary outcome, whether the P value of the primary outcome was statistically significant and the level of heterogeneity in age between the treatment groups (measured using the I2 statistic). The association between the quality of allocation concealment and the P value of the primary outcome was assessed using a kernel density plot, while the association between the quality of allocation concealment and whether the P value was statistically significant was assessed using logistic regression.ResultsTrials that used inadequate concealment methods were more likely to report statistically significant findings than trials that used good or adequate methods (OR 1.90; 95% CI: 0.91 to 3.95; P = .09). The values of I2 for trials that used good, adequate, inadequate and unclear concealment methods were 0%, 1.0%, 32.6%, and 93.8%, respectively.ConclusionThere is evidence of an association between poor allocation concealment methods and statistical significance of the primary outcome. Trials that use inadequate allocation concealment methods are more likely to have statistically significant P values compared with trials using good or adequate allocation concealment methods.