Department of Epidemiology, School of Public Health, Iran University of Medical Sciences, Tehran, Iran.
Faculty of Medicine, School of Public Health, Imperial Clinical Trials Unit, Imperial College London, London, UK.
BMC Med Res Methodol. 2021 Oct 9;21(1):206. doi: 10.1186/s12874-021-01405-8.
Identifying strategies to optimize participation in health studies is one of the major concerns for researchers. The purpose of this study was to evaluate the efficiency of different invitation strategies on participation rate in the Employees' Health Cohort Study of Iran (EHCSIR).
Two cluster-randomized trials were carried out to assess the outcomes of different invitation strategies. In the first phase, 7 units with 1880 employees (3 hospitals, 3 health centers, and 1 office) were assigned to the three parallel modes of invitation: 1) invitation letter, 2) phone call and 3) Short Message Service (SMS). In the second phase, 6 hospitals with 1633 employees were allocated to two invitation methods: 1) invitation letter, 2) invitation letter plus EHCSIR project introduction video. All groups were followed up by phone calls. A logistic mixed-effects model was used to compare the effectiveness of the strategies. The cost-effectiveness of the interventions was also compared.
In the first phase, the participation rates in the invitation letter, phone call, and SMS groups were 27.04% (182/673), 21.55% (131/608), and 22.54% (135/599), respectively. Using an invitation letter was significantly more successful than SMS (Adjusted Odds Ratio = 1.80, 95% CI =1.14 to 2.85). Average Cost-Effectiveness Ratios (ACER) were $1.37, $1.42, and $1.55 for the invitation letter, phone call, and SMS, respectively. In the second phase, adding a project introduction video to the invitation letter did not significantly influence the participation rate (Adjusted OR = 0.58, 95% CI =0.24 to 1.36). The ACER was $1.21 for the invitation letter only and $2.01 for the invitation letter plus the introduction video.
In comparison with the phone call and SMS, the invitation letter is the most effective invitation method for public sector employees to participate in a cohort study. Sending an introduction video did not significantly increase the participation rate compared to sending an invitation letter only.
确定优化健康研究参与度的策略是研究人员关注的主要问题之一。本研究旨在评估不同邀请策略对伊朗职工健康队列研究（EHCSIR）参与率的影响。
进行了两项集群随机试验以评估不同邀请策略的结果。在第一阶段，将 7 个单位的 1880 名员工（3 家医院、3 家卫生中心和 1 家办公室）分为 3 种平行邀请模式：1）邀请信，2）电话邀请，3）短信服务（SMS）。在第二阶段，将 6 家医院的 1633 名员工分配至两种邀请方法：1）邀请信，2）邀请信加 EHCSIR 项目介绍视频。所有组均通过电话进行随访。采用逻辑混合效应模型比较策略的有效性。还比较了干预措施的成本效益。
在第一阶段，邀请信、电话邀请和短信邀请组的参与率分别为 27.04%（182/673）、21.55%（131/608）和 22.54%（135/599）。与 SMS 相比，使用邀请信明显更为成功（调整后的优势比[OR] = 1.80，95%置信区间[CI] = 1.14 至 2.85）。邀请信、电话邀请和短信邀请的平均成本效益比（ACER）分别为 1.37、1.42 和 1.55。在第二阶段，向邀请信中添加项目介绍视频并未显著影响参与率（调整后的 OR = 0.58，95%CI = 0.24 至 1.36）。仅邀请信的 ACER 为 1.21，邀请信加介绍视频的 ACER 为 2.01。
与电话邀请和短信邀请相比，邀请信是邀请公共部门员工参加队列研究的最有效邀请方式。与仅发送邀请信相比，发送介绍视频并未显著提高参与率。
