BACKGROUND Cohort studies are pivotal in understanding the natural history, and to thereby determine the incidence of a disease. The conduct of large-scale community-based cohort studies is challenging with reference to money, manpower and time. Further, attrition inherent to cohort studies can affect the power, and thereby the study's validity. Our objective was to estimate the percentage of participant withdrawal and to subsequently understand reasons for the same in the Vellore Typhoid Surveillance (VTS) cohort. METHODS VTS study, a prospective community-based pediatric cohort, was established in a semi-urban settlement of Vellore to estimate the incidence rate of typhoid fever. An active weekly surveillance identified children with fever, and blood cultures were performed for fevers of ≥3 days. Reasons for participant drop-out in the cohort were documented. Nine focus group discussions (FGD), each with 5 to 7 parents/primary caregivers of former as well current participants were conducted separately, to understand reasons for consent withdrawal as well as the good aspects of the study that the current participants perceived. A descriptive, as well as an interpretative account of the themes that emerged from the FGDs were done. RESULTS Of the 5639 children in the VTS cohort, 404 (7.2%) withdrew consent during the 12-month surveillance. Of these, 50% dropped out due to migration from study area; 18.1% as their parents were unhappy with the blood draws for blood culture; and 14.4% did not clearly put forth the reason for consent withdrawal. Being from an orthodox background, high socio-economic status and joint family were associated with a decision to drop-out. Frequent and voluminous blood draws, male field research assistants (FRA) making weekly home-visits, the perception that inquiring about fever made their child fall sick, and that the study clinic did not initiate antibiotics immediately, were the important themes that emerged from the FGDs conducted among drop-outs. CONCLUSION Our study showed that specific beliefs and behaviours within the community influenced the drop-out rate of the VTS cohort. Background characteristics and perceptions that exist, along with attrition data from previous cohort studies in the specific community are important to be considered while implementing large-scale cohort studies.

中文翻译：

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为什么参与者退出：印度南部韦洛尔建立的前瞻性儿科发烧监测队列的研究结果。

背景技术队列研究对于理解自然史并由此确定疾病的发病率至关重要。开展大规模社区队列研究在资金、人力和时间方面具有挑战性。此外，队列研究固有的损耗会影响功效，从而影响研究的有效性。我们的目标是估计参与者退出的百分比，并随后了解韦洛尔伤寒监测 (VTS) 队列中退出的原因。方法 VTS 研究是一项基于社区的前瞻性儿科队列研究，在韦洛尔的一个半城市定居点建立，旨在估计伤寒的发病率。每周积极监测发现发烧儿童，并对发烧≥3天的儿童进行血培养。记录了参与者退出队列的原因。分别进行了九次焦点小组讨论 (FGD)，每次有 5 至 7 名前参与者和当前参与者的父母/主要照顾者，以了解撤回同意的原因以及当前参与者认为研究的优点。对 FGD 中出现的主题进行了描述性和解释性说明。结果 在 VTS 队列中的 5639 名儿童中，404 名 (7.2%) 在 12 个月的监测期间撤回了同意。其中，50%因从研究地区迁移而退出；18.1%是因为父母对抽血血培养不满意；14.4%没有明确提出撤回同意的原因。来自正统背景、较高的社会经济地位和联合家庭与辍学的决定有关。频繁、大量的抽血、男性现场研究助理 (FRA) 每周家访、询问发烧情况会导致孩子生病的看法以及研究诊所没有立即启动抗生素，这些都是研究中出现的重要主题。在辍学者中进行 FGD。结论 我们的研究表明，社区内的特定信仰和行为影响 VTS 队列的退出率。在实施大规模队列研究时，必须考虑现有的背景特征和看法，以及特定社区先前队列研究的流失数据。