Warwick Clinical Trials Unit, Warwick Medical School, University of Warwick, Gibbett Hill Road, Coventry CV4 7AL, United Kingdom.
J Clin Epidemiol. 2012 Jan;65(1):90-9. doi: 10.1016/j.jclinepi.2011.04.011. Epub 2011 Aug 9.
Follow-up data were collected using postal questionnaires and if participants did not respond, then data was collected using telephone interviews. The objectives of this study were to examine, for the two methods, how respondents differed in characteristics and whether the observed treatment difference varied.
A large clinical trial of lower back pain.
About 60% (98/163) of the nonresponders to postal questionnaire provided data by telephone, which increased the overall response rate by 14% (from 71% to 85%). A consistent treatment difference was found across the methods for the outcome measures at 12 months, implying that the observed treatment effect had not been modified. There were some differences between the participants: responders of postal questionnaire were older, likely to be female, white (ethnic origin), not working, with less disability of back pain, compared with those who responded by a telephone interview. At 12 months, there was greater improvement in back pain, disability, and general health for those who responded by postal questionnaires.
Researchers should consider the use of more than one method of collecting data as this increases response rate, participant representativeness, and enhances precision of effect estimates.
通过邮寄问卷收集随访数据，如果参与者未回复，则通过电话访谈收集数据。本研究的目的是检查两种方法中，回复者在特征上有何不同，以及观察到的治疗差异是否有所变化。
一项针对腰痛的大型临床试验。
约 60%（98/163）未回复邮寄问卷的人通过电话提供了数据，这将总体回复率提高了 14%（从 71%提高到 85%）。对于 12 个月时的结局指标，两种方法均发现了一致的治疗差异，这意味着观察到的治疗效果没有改变。参与者之间存在一些差异：通过邮寄问卷回复的参与者年龄更大，更可能是女性、白人（种族）、不工作、腰痛残疾程度较低，与通过电话访谈回复的参与者相比。在 12 个月时，通过邮寄问卷回复的参与者在腰痛、残疾和一般健康方面的改善更大。
研究人员应考虑使用多种方法收集数据，这可以提高回复率、参与者代表性，并提高效果估计的精度。
