López Rodrigo, Frydenberg Morten, Baelum Vibeke
Department of Periodontology, Royal Dental College, University of Aarhus, Denmark.
Eur J Oral Sci. 2008 Oct;116(5):405-11. doi: 10.1111/j.1600-0722.2008.00567.x.
Periodontal researchers frequently use case-control studies, but information on participation rates and the reasons for participation are often missing in the publications, thus hindering the assessment of the validity of those studies. A nested case-control study based on a well-defined population was used to (i) describe the patterns of participation; (ii) show how some associations can be biased; and (iii) illustrate how inverse probability weights can be applied to reduce bias. Differential subject participation was quantified using the ratio between participation for each level and the overall participation. Possible biased associations were illustrated using the odds ratios found for eligible and participant subjects. Finally, we used the estimated probability that an individual participates in the case-control study conditional on that individual's covariate pattern, as observed in the screening study to attempt bias reduction. Considerable differential participation was observed for selected factors, including age, annual tuitions and fees, parental income, and parental education. The strategy used for adjustment of bias resulted in some degree of bias reduction. These findings challenge the inferential validity of many studies on periodontitis. The design and conduct of these studies should aim to improve subject participation and must consider and minimize this potential source of bias.
牙周病研究人员经常使用病例对照研究，但出版物中往往缺少参与率及参与原因的相关信息，从而妨碍了对这些研究有效性的评估。一项基于明确界定人群的巢式病例对照研究被用于：（i）描述参与模式；（ii）展示某些关联如何产生偏差；以及（iii）说明如何应用逆概率权重来减少偏差。使用每个水平的参与率与总体参与率之比来量化不同受试者的参与情况。通过符合条件和参与研究的受试者的比值比来说明可能存在偏差的关联。最后，我们利用在筛查研究中观察到的个体协变量模式条件下个体参与病例对照研究的估计概率来尝试减少偏差。在年龄、年度学费、父母收入和父母教育程度等选定因素方面观察到了显著的差异参与情况。用于调整偏差的策略在一定程度上减少了偏差。这些发现对许多牙周炎研究的推断有效性提出了挑战。这些研究的设计和实施应旨在提高受试者参与度，并且必须考虑并尽量减少这种潜在的偏差来源。
