Kandiyali Rebecca, Thom Howard, Young Amber E, Greenwood Rosemary, Welton Nicky J
1Population Health Sciences, Bristol Medical School, University of Bristol, Bristol, UK.
2University Hospitals Bristol NHS Foundation Trust, Bristol, UK.
Pilot Feasibility Stud. 2020 Jan 31;6:8. doi: 10.1186/s40814-019-0543-1. eCollection 2020.
Patients with burn injuries may receive a skin graft to achieve healing in a timely manner. However, in around 7% of cases, the skin graft is lost (fails to attach to the wound site) and a re-grafting procedure is necessary. It has been hypothesised that low-friction (smooth, more slippery) bedding may reduce the risk of skin-graft loss. A before and after feasibility study comparing low-friction with standard bedding in skin-grafted patients was conducted in order to collect proof of concept data. The resulting relative risk on the primary outcome (number of patients with skin graft failure) for the non-randomised study provided no evidence of effect but had a large standard error. The aim of this study is to see if an appropriately powered randomised control trial would be worthwhile.
A probabilistic decision-analytic model was constructed to compare low-friction bedding to standard care in a population of burn patients who have undergone skin grafting. Results from the before and after study were used as model inputs. The sensitivity of results to bias in the relative risk of graft loss was conducted. Low-friction bedding is considered optimal if expected incremental net benefit (INB) is positive. Uncertainty is assessed using cost-effectiveness acceptability curves. Expected Value of Perfect Partial Information (EVPPI) provides an upper bound for the potential net health benefits of new research for given model input.
At a willingness to pay threshold of £20,000 per QALY, INB = £151 (95% Credible Interval (CrI) -142 to 814), marginally favouring low-friction bedding but with high uncertainty (probability of being cost-effective 70.5%). Expected value of perfect information (EVPI) per patient was £20.29, which results in a population EVPI of £174,765 over a 10-year lifetime for the technology (based on 1000 patients per year who would benefit from the intervention). The parameter contributing most to the uncertainty was the inpatient care cost, i.e. information that could be obtained from the audit of practice and without an expensive trial. These findings were robust to a wide-range of assumptions about the potential bias due to the observational nature of the comparative evidence.
Our study results suggest that an RCT (randomised controlled trial) is unlikely to be worthwhile, but there may be value in a study to estimate the re-graft rates and associated costs in this population.
烧伤患者可能需要接受皮肤移植以实现及时愈合。然而，在约7%的病例中，皮肤移植会失败（无法附着在伤口部位），需要进行再次移植手术。有人提出，低摩擦（光滑、更滑）的床上用品可能会降低皮肤移植失败的风险。为了收集概念验证数据，对皮肤移植患者中低摩擦床上用品与标准床上用品进行了一项前后可行性研究。非随机研究中主要结局（皮肤移植失败患者数量）的相对风险结果未提供效果证据，但标准误差较大。本研究的目的是确定一项样本量合适的随机对照试验是否值得开展。
构建了一个概率性决策分析模型，以比较低摩擦床上用品与标准护理对接受皮肤移植的烧伤患者群体的效果。前后研究的结果用作模型输入。对移植失败相对风险中的偏差对结果的敏感性进行了分析。如果预期增量净效益（INB）为正，则低摩擦床上用品被认为是最佳选择。使用成本效益可接受性曲线评估不确定性。完美部分信息的预期价值（EVPPI）为给定模型输入下新研究的潜在净健康效益提供了上限。
在每质量调整生命年（QALY）支付意愿阈值为20,000英镑时，INB = 151英镑（95%可信区间（CrI）为-142至814英镑），略微倾向于低摩擦床上用品，但不确定性较高（具有成本效益的概率为70.5%）。每位患者的完美信息预期价值（EVPI）为20.29英镑，这导致该技术在10年寿命期内的总体EVPI为174,765英镑（基于每年将从干预中受益的1000名患者）。对不确定性贡献最大的参数是住院护理成本，即可以从实践审计中获得且无需进行昂贵试验的信息。这些发现对于因比较证据的观察性质而导致的潜在偏差的广泛假设具有稳健性。
我们的研究结果表明，一项随机对照试验（RCT）不太可能值得开展，但对该人群的再次移植率及相关成本进行估计的研究可能具有价值。
