University Health Network, University of Toronto, Toronto, M5T 2S8, Canada.
Institute of Medical Science, University of Toronto, City, ON, M5S 1A8, Canada.
BMC Med Res Methodol. 2017 Sep 6;17(1):133. doi: 10.1186/s12874-017-0418-1.
Longitudinal studies using data collected as part of usual care risk providing biased results if visit times are related to the outcome of interest. Statistical methods for mitigating this bias are available but rarely used. This lack of use could be attributed to a lack of need or to a lack of awareness of the issue.
We performed a systematic review of longitudinal studies that used data collected as part of patients' usual care and were published in MEDLINE or EMBASE databases between January 2005 through May 13 2015. We asked whether the extent of and reasons for variability in visit times were reported on, and in cases where there was a need to account for informativeness of visit times, whether an appropriate method was used.
Of 44 eligible articles, 57% (n = 25) reported on the total follow-up time, 7% (n = 3) on the gaps between visits, and 57% (n = 25) on the number of visits per patient; 78% (n = 34) reported on at least one of these. Two studies assessed predictors of visit times, and 86% of studies did not report enough information to assess whether there was a need to account for informative follow-up. Only one study used a method designed to account for informative visit times.
The low proportion of studies reporting on whether there were important predictors of visit times suggests that researchers are unaware of the potential for bias when data is collected as part of usual care and visit times are irregular. Guidance on the potential for bias and on the reporting of longitudinal studies subject to irregular follow-up is needed.
如果就诊时间与感兴趣的结局相关，那么利用常规护理收集的数据进行纵向研究可能会产生有偏的结果。有一些用于减轻这种偏倚的统计方法，但很少被使用。这种低使用率可能归因于对这一问题缺乏认识，或者对其必要性认识不足。
我们对 2005 年 1 月至 2015 年 5 月 13 日期间在 MEDLINE 或 EMBASE 数据库中发表的利用常规护理收集的数据进行了系统综述，这些研究为纵向研究。我们询问了就诊时间的变异性程度和原因是否有报道，在需要考虑就诊时间信息量的情况下，是否使用了适当的方法。
在 44 篇符合条件的文章中，57%（n=25）报告了总的随访时间，7%（n=3）报告了就诊间隔，57%（n=25）报告了每位患者的就诊次数；78%（n=34）至少报告了其中之一。两项研究评估了就诊时间的预测因素，86%的研究没有报告足够的信息来评估是否需要考虑有信息量的随访。仅有一项研究使用了旨在考虑信息量就诊时间的方法。
很少有研究报告就诊时间是否存在重要预测因素，这表明当数据是作为常规护理的一部分收集且就诊时间不规律时，研究人员可能没有意识到存在偏倚的可能性。需要有关于潜在偏倚和不规则随访的纵向研究报告的指南。
