Digestive Disease Research Center, Shariati Hospital, Tehran University of Medical Sciences, Tehran, Iran.
PLoS One. 2012;7(3):e32711. doi: 10.1371/journal.pone.0032711. Epub 2012 Mar 1.
Control selection is a major challenge in epidemiologic case-control studies. The aim of our study was to evaluate using hospital versus neighborhood control groups in studying risk factors of esophageal squamous cell carcinoma (ESCC).
METHODOLOGY/PRINCIPAL FINDINGS: We compared the results of two different case-control studies of ESCC conducted in the same region by a single research group. Case definition and enrollment were the same in the two studies, but control selection differed. In the first study, we selected two age- and sex-matched controls from inpatient subjects in hospitals, while for the second we selected two age- and sex-matched controls from each subject's neighborhood of residence. We used the test of heterogeneity to compare the results of the two studies. We found no significant differences in exposure data for tobacco-related variables such as cigarette smoking, chewing Nass (a tobacco product) and hookah (water pipe) usage, but the frequency of opium usage was significantly different between hospital and neighborhood controls. Consequently, the inference drawn for the association between ESCC and tobacco use did not differ between the studies, but it did for opium use. In the study using neighborhood controls, opium use was associated with a significantly increased risk of ESCC (adjusted OR 1.77, 95% CI 1.17-2.68), while in the study using hospital controls, this was not the case (OR 1.09, 95% CI 0.63-1.87). Comparing the prevalence of opium consumption in the two control groups and a cohort enrolled from the same geographic area suggested that the neighborhood controls were more representative of the study base population for this exposure.
CONCLUSIONS/SIGNIFICANCE: Hospital and neighborhood controls did not lead us to the same conclusion for a major hypothesized risk factor for ESCC in this population. Our results show that control group selection is critical in drawing appropriate conclusions in observational studies.
在流行病学病例对照研究中，对照选择是一个主要挑战。我们的研究目的是评估使用医院对照和社区对照来研究食管鳞癌（ESCC）的危险因素。
方法/主要发现：我们比较了同一研究组在同一地区进行的两项不同 ESCC 病例对照研究的结果。两项研究的病例定义和纳入标准相同，但对照选择不同。在第一项研究中，我们从医院住院患者中选择了两个年龄和性别匹配的对照；而在第二项研究中，我们从每个患者的居住社区中选择了两个年龄和性别匹配的对照。我们使用异质性检验比较了两项研究的结果。我们发现，与吸烟、咀嚼 Nass（一种烟草产品）和水烟（水烟管）使用等烟草相关变量相关的暴露数据没有显著差异，但医院对照和社区对照的鸦片使用频率有显著差异。因此，ESCC 与烟草使用之间关联的推断在两项研究中没有差异，但在鸦片使用方面则有差异。在使用社区对照的研究中，鸦片使用与 ESCC 的风险显著增加相关（调整后的 OR 为 1.77，95%CI 为 1.17-2.68），而在使用医院对照的研究中则不然（OR 为 1.09，95%CI 为 0.63-1.87）。比较两个对照组和同一地理区域招募的队列中鸦片使用的流行率表明，对于这种暴露，社区对照更能代表研究基础人群。
结论/意义：在该人群中，对于 ESCC 的一个主要假设风险因素，医院对照和社区对照没有使我们得出相同的结论。我们的结果表明，对照选择对于在观察性研究中得出适当结论至关重要。
