Department of Surgery and Cancer, Imperial College London, London, UK.
Wolfson Institute for Preventive Medicine, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK.
J Med Screen. 2021 Dec;28(4):419-425. doi: 10.1177/0969141321997480. Epub 2021 Feb 27.
To evaluate the effect of general practitioner endorsement accompanying the screening kit rather than with the invitation letter on participation in the NHS Bowel Cancer Screening Programme and on the socioeconomic gradient in participation in the Programme.
The NHS Bowel Cancer Screening Programme in England is delivered via five regional hubs. In early 2016, we carried out a cluster-randomised trial, with hub-day of invitation as the randomisation unit. We randomised 150 hub-days of invitation to the intervention group, GP endorsement on the letter accompanying the guaiac faecal occult blood testing kit (75 hub-days, 197,366 individuals) or control, usual letter (75 hub-days, 197,476 individuals). The endpoint was participation, defined as return of a valid kit within 18 weeks of initial invitation. Because of the cluster randomisation, data were analysed by a hierarchical logistic regression, allowing a random effect for date of invitation. Socioeconomic status was represented by the index of multiple deprivation.
Participation was 59.4% in the intervention group and 58.7% in the control group, a significant difference ( = 0.04). There was no heterogeneity of the effect of intervention by index of multiple deprivation. We found that there was some confounding between date and screening episode order (first or subsequent screen). This in turn may have induced confounding with age and slightly diluted the result.
General practitioner endorsement induces a modest increase in participation in bowel cancer screening, but does not affect the socioeconomic gradient. When considering cluster randomisation as a research method, careful scrutiny of potential confounding is indicated in advance if possible and in analysis otherwise.
评估在 NHS 大肠癌筛查计划中，与邀请信相比，在筛查工具包上附上全科医生背书对参与度的影响，以及对参与计划的社会经济梯度的影响。
英格兰的 NHS 大肠癌筛查计划通过五个区域中心进行。2016 年初，我们进行了一项集群随机试验，以邀请日作为随机单位。我们将 150 个邀请日随机分配到干预组，在检测试剂盒的随附信件上附上全科医生背书（75 个邀请日，197366 人）或对照组，即通常的信件（75 个邀请日，197476 人）。终点是参与度，定义为在初始邀请后的 18 周内返回有效的试剂盒。由于聚类随机化，数据通过分层逻辑回归进行分析，允许日期的随机效应。社会经济地位由多种剥夺指数表示。
干预组的参与率为 59.4%，对照组为 58.7%，差异显著（ = 0.04）。干预效果与多种剥夺指数之间没有异质性。我们发现，日期和筛查期顺序（初次或后续筛查）之间存在一定的混杂。这反过来可能导致了年龄的混杂，略微稀释了结果。
全科医生背书适度增加了大肠癌筛查的参与度，但不影响社会经济梯度。在考虑将聚类随机化作为一种研究方法时，如果可能的话，在分析之前应仔细检查潜在的混杂因素，否则在分析中应进行检查。
