The Canadian Bandaging Trial was adequately powered to detect a minimally important difference of 4-weeks in median healing time between 4LBs and SSBs. We put much emphasis on testing the compression technologies within an evidence-informed approach to care i.e. a protocol for venous leg ulcer assessment and management, well developed training procedures, and well prepared RNs. With these elements in place, results from our trial suggest that the two compression bandaging technologies tested are not different in terms of time-to-healing, recurrence rates, HRQL, or pain. However, individuals were less satisfied with 4LB, with more reporting problems with the bandaging system.
These healing results should be viewed in the context of all the trials making this comparison. O'Meara et al. [33
] conducted a meta-analysis of individual patient data to evaluate the intervention effect of 4LBs relative to SSBs. They concluded that venous leg ulcers in patients treated with 4LBs heal faster, on average, than those treated with SSBs; and the benefits were consistent across patients with differing prognostic profiles. In contrast, our trial (the largest to date), put much emphasis on other aspects of venous leg ulcer care, namely an evidence-informed protocol of care and well-prepared RNs in administering these bandaging systems. With these elements of care in place, there were no differences between the technologies except that individuals may have more problems with 4LBs.
In the O'Meara meta-analysis, the intervention effect estimate from the UK VenUS I was weighted heavily towards the pooled effect estimate (i.e. 63% from this trial among five others). As the only other large scale trial comparable to this Canadian RCT, the UK VenUS I showed that with 4LBs there was a shorter healing time. We were unable to replicate this finding despite comparable sample sizes. Several factors may be contributing to this difference. Nurse wound-care teams in Canada have more training and experience in both
technologies. The SSB was newly introduced to UK primary care just prior to their trial and there was a higher withdrawal rate in the SSB arm of the VenUS I trial. The UK authors [43
] state they "investigated the introduction
(their emphasis) of a high-level compression bandage system into a setting where an acceptable mode of compression was already in use" and a reasonable conclusion is that short stretch is "a useful alternative" (pg. 1298). Based on the experience from the UK trial, our Canadian sites had initial and ongoing training including quality checks to ensure adherence to the evidence-informed assessment and management protocol for either bandage. In the Canadian trial, the nurses may have been more confident and competent in delivery of both bandage systems thus reducing operator experience/preference as a source of bias. Another context factor may be important. Canadian site teams actively participated in the development of the protocol in their local settings to make it as seamless as possible within their normal delivery of care. Based on best practice recommendations, they carefully constructed an approach to adhere to key aspects of leg ulcer assessment and management. For example, the initial comprehensive assessment may have been carried out by specially trained nurses in the home with portable equipment whereas at some sites, it was more feasible at a designated clinic location where a wound expert and equipment were centralized.
In considering the site differences our team thought there were factors that should be further explored in a future study. Although we tracked key elements of the evidence-informed protocol (comprehensive assessment and use of compression), and all sites delivered these recommendations, there may be subtle differences contributing to healing rates. For example, some sites were newer and less experienced and may have been less supported regionally in the delivery of care. As well, because the trial was conducted in a large number of jurisdictions the referral and wait-times may have varied influencing the time to assessment which may have affected outcomes. Unfortunately we did not have data to drill down and explore these issues in this trial.
Lastly, healing in the Canadian trial for 4LB was 62 days compared to 77 days with SSB - both much shorter than the UK study population. This may be partly explained by their healing outcome being complete healing of all ulcers not just a reference ulcer. Nevertheless in examining healing over time compared to previous trials (Table ), the Canadian group had higher proportions healed at 12, 16, 24 and 52 week time-points for both SSB and 4LB except SSB at 16 weeks in the Partsch study [45
Healing Rates at 12, 16, 24, and 52 weeks in trials comparing four-layer and short-stretch bandages
From this large Canadian trial the key message regarding healing is 'when delivered in the practice context of trained RNs and an evidence-informed protocol choice of bandage system (4LB and SSB) does not materially affect healing times, recurrence rates, HRQL, or pain'. Expenditures and resource use should be another consideration. According to results from the UK VenUS I trial on average, 4LB was associated with greater health benefits and lower costs than SSB. In a separate cost-effectiveness analysis, we are addressing whether this finding holds in the community care setting in Canada.
Limitations of the Study
This trial has some limitations that should be considered when interpreting the results. It might be considered a limitation that nurses providing care were involved in collection of outcomes data. Blinding the nurse to the compression technology was not feasible and once bandages were applied it would have been excessively intrusive (and monumentally expensive) to remove them solely for the purpose of an outcome assessment. However, our small team of dedicated specially trained nurses, ensured expert, quality outcome assessments by measuring healing in a rigorous and consistent manner and this was validated by photo assessment by an expert remote from the site of care and who was blinded to allocation group. The results may not be generalizable beyond the study population but since the trial took place in multiple sites in three provinces (Ontario, Manitoba and Saskatchewan) that included both urban and rural locations, and culturally mixed populations this should increase the likelihood of generalizability.
This RCT is the largest community wound trial conducted in Canada and the largest trial evaluating these two compression technologies internationally. The trial's pragmatic approach emulated the usual delivery of assessment and care with healing outcomes confirmed by an individual blinded to study arm. The comparative effectiveness of SSB and 4LB systems in healing ulcers will be more precisely addressed when the Canadian trial is added to the meta-analysis from the Cochrane Wounds Group [33
] recognizing that context is important and contributing to the sub-groups analysis of trial result by country of study.