Gyarmathy V Anna, Johnston Lisa G, Caplinskiene Irma, Caplinskas Saulius, Latkin Carl A
Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA.
University of California, San Francisco, Global Health Sciences, San Francisco, CA, USA; Tulane University, School of International Public Health and Tropical Medicine, New Orleans, LA, USA.
Drug Alcohol Depend. 2014 Feb 1;135:71-7. doi: 10.1016/j.drugalcdep.2013.11.020. Epub 2013 Dec 3.
Respondent driven sampling (RDS) and incentivized snowball sampling (ISS) are two sampling methods that are commonly used to reach people who inject drugs (PWID).
We generated a set of simulated RDS samples on an actual sociometric ISS sample of PWID in Vilnius, Lithuania ("original sample") to assess if the simulated RDS estimates were statistically significantly different from the original ISS sample prevalences for HIV (9.8%), Hepatitis A (43.6%), Hepatitis B (Anti-HBc 43.9% and HBsAg 3.4%), Hepatitis C (87.5%), syphilis (6.8%) and Chlamydia (8.8%) infections and for selected behavioral risk characteristics.
The original sample consisted of a large component of 249 people (83% of the sample) and 13 smaller components with 1-12 individuals. Generally, as long as all seeds were recruited from the large component of the original sample, the simulation samples simply recreated the large component. There were no significant differences between the large component and the entire original sample for the characteristics of interest. Altogether 99.2% of 360 simulation sample point estimates were within the confidence interval of the original prevalence values for the characteristics of interest.
When population characteristics are reflected in large network components that dominate the population, RDS and ISS may produce samples that have statistically non-different prevalence values, even though some isolated network components may be under-sampled and/or statistically significantly different from the main groups. This so-called "strudel effect" is discussed in the paper.
应答驱动抽样（RDS）和激励性滚雪球抽样（ISS）是两种常用于接触注射吸毒者（PWID）的抽样方法。
我们在立陶宛维尔纽斯的一个实际的注射吸毒者社会计量学激励性滚雪球抽样样本（“原始样本”）上生成了一组模拟应答驱动抽样样本，以评估模拟应答驱动抽样估计值与原始激励性滚雪球抽样样本中艾滋病毒（9.8%）、甲型肝炎（43.6%）、乙型肝炎（抗-HBc 43.9%和HBsAg 3.4%）、丙型肝炎（87.5%）、梅毒（6.8%）和衣原体（8.8%）感染以及选定行为风险特征的患病率在统计学上是否有显著差异。
原始样本由249人（占样本的83%）的一个大组分和13个由1至12人组成的小组分组成。一般来说，只要所有种子都从原始样本的大组分中招募，模拟样本就只是简单地重现大组分。对于感兴趣的特征，大组分与整个原始样本之间没有显著差异。在360个模拟样本点估计中，总共99.2%在感兴趣特征的原始患病率值的置信区间内。
当总体特征反映在主导总体的大型网络组分中时，应答驱动抽样和激励性滚雪球抽样可能产生患病率值在统计学上无差异的样本，尽管一些孤立的网络组分可能抽样不足和/或在统计学上与主要群体有显著差异。本文讨论了这种所谓的“果馅卷效应”。
