Clinics for Vascular Surgery, Kantonsspital St. Gallen, St. Gallen, Switzerland.
Swiss Cardiovascular Centre, Department of Cardiovascular Surgery, University Hospital Bern and University of Bern, Bern, Switzerland.
PLoS One. 2019 Mar 18;14(3):e0213822. doi: 10.1371/journal.pone.0213822. eCollection 2019.
In outcome research, incomplete follow-up is a major, yet potentially correctable source of bias. Cross-sectional surveys may theoretically increase completeness of follow-up, but low response rates are reported typically. We investigated whether a pre-notification letter improved patient availability for follow-up phone interviews and thereby improved cross-sectional survey yield.
A consecutive series of vascular patients was randomly divided into a trial and a validation population. The trial population was then randomized 1:1 to one of two cross-sectional contact strategies: Strategy 1 consisted of direct contact attempts by up to 12 systematically timed phone calls, whereas Strategy 2 used a personalized pre-notification letter to arrange for scheduled phone call interviews. Response rates, average time and efforts needed per patient and overall survey duration were compared. Subsequently, trial findings were externally validated in the validation population.
Of 728 consecutive patients, 370 were allocated to the trial population. Trial patients contacted by strategy 1 (n = 183) had a similar profile when compared to trial patients contacted by strategy 2 (n = 187). Follow-up periods following surgery (54.3 versus 53.6 months) and all-cause mortality rates (21.3% versus 18.7%) were comparable between the trial groups. Cross-sectional information on survival outcomes was almost complete after both contact strategies (99.5% versus 98.9%, P = 1.0). In 144/187 strategy 2 patients (77%) interviews were scheduled successfully necessitating significantly less contact attempts (median of 1.3 versus 2.3 per patient, P<0.0001). However, invested time per patient was similar between the groups (median of 10.1 versus 9.6 minutes), and survey strategy 1 completed earlier (median time to contact 4 versus 11 days, P<0.0001). Therefore, strategy 1 was validated in the validation population (n = 358): a low lost to follow-up rate below 1% (P = 1.0) was reconfirmed necessitating an average of 2.3 contact attempts per patient.
Both contact strategies were equally successful in contacting almost all patients cross-sectionally. If systematically timed, direct phone calls were less complicated to organize and faster completed. Given the low time and effort per patient, outcome studies should invest in systematic follow-up surveys to minimize attrition bias.
在结局研究中，不完整的随访是一个主要的、但潜在可纠正的偏倚来源。横断面调查理论上可以增加随访的完整性，但通常报告的应答率较低。我们研究了预通知信是否可以提高患者接受随访电话访谈的可用性，从而提高横断面调查的效果。
连续系列的血管患者被随机分为试验组和验证组。然后，试验组被随机分为 1:1 分为两种横断面联系策略：策略 1 包括最多 12 次系统定时电话尝试的直接联系尝试，而策略 2 使用个性化预通知信来安排预约电话访谈。比较了应答率、每位患者的平均时间和努力、以及总体调查持续时间。随后，在验证组中对试验结果进行了外部验证。
728 例连续患者中，370 例被分配到试验组。通过策略 1 联系的试验患者（n = 183）与通过策略 2 联系的试验患者（n = 187）的特征相似。手术（54.3 与 53.6 个月）和全因死亡率（21.3%与 18.7%）的随访期在试验组之间相似。两种联系策略后，生存结局的横断面信息几乎完全（99.5%与 98.9%，P = 1.0）。在 187 例策略 2 患者中的 144 例（77%）成功预约了访谈，这需要的联系尝试明显减少（中位数每位患者 1.3 次与 2.3 次，P<0.0001）。然而，两组之间每位患者的投入时间相似（中位数为 10.1 与 9.6 分钟），并且策略 1 更早完成（中位联系时间为 4 与 11 天，P<0.0001）。因此，策略 1 在验证组（n = 358）中得到验证：低失访率低于 1%（P = 1.0），需要每位患者平均 2.3 次联系尝试。
两种联系策略在横向联系几乎所有患者方面都同样成功。如果系统地定时进行，直接电话联系的组织更为简单，且完成速度更快。鉴于每位患者的时间和精力投入较低，结局研究应投资于系统的随访调查，以最大限度地减少损耗偏倚。
