FHI, Research Triangle Park, NC 27709, USA.
Contemp Clin Trials. 2011 Jul;32(4):512-6. doi: 10.1016/j.cct.2011.03.008. Epub 2011 Mar 5.
Poor retention can reduce study power and thwart randomization, possibly resulting in biased estimates of effect. Some HIV prevention trials conducted in developing countries have been challenged by high loss to follow-up. Identifying factors associated with non-retention could lead to recruitment of women more likely to remain in the trial, potentially yielding greater efficiency and validity.
We summarized retention rates and, using Cox regression, evaluated factors associated with non-retention in four trials of two candidate vaginal microbicides (1% C31G or SAVVY® and 6% cellulose sulfate or CS) conducted in multiple sub-Saharan African countries. We defined retention as completion of the trial, including those with an HIV outcome. Non-retention comprised participants randomized to a study arm who were either lost to follow-up or discontinued prior to infection with HIV.
7,367 women were enrolled and randomized in the four trials; 7,086 are included in this analysis. 1,514 (21.4%) participants were either lost to follow-up or had early discontinuation. In the final Cox model, the following baseline factors were associated with non-retention: younger age (hazard ratio [HR] = 0.95); less education (HR = 0.97); condom use at last sex (HR = 1.18); larger number of sex acts in a typical week (HR = 1.01); and baseline candidiasis or bacterial vaginosis (HR = 1.12).
Younger and less educated women were more difficult to retain in these microbicide trials. But these same traits may be associated with higher HIV infection rates. Enhanced retention methods focused on those at highest risk of non-retention and possibly infection will optimize study efficiency and validity.
较差的保留率可能会降低研究效力并破坏随机分组，从而导致对疗效的估计产生偏差。一些在发展中国家开展的 HIV 预防试验因失访率高而受到挑战。确定与失访相关的因素可能会导致招募更有可能完成试验的女性，从而提高效率和有效性。
我们总结了四项候选阴道杀微生物剂（1％C31G 或 SAVVY®和 6％硫酸纤维素或 CS）试验的保留率，并使用 Cox 回归分析评估了与失访相关的因素。我们将保留定义为完成试验，包括发生 HIV 结局的参与者。失访包括随机分配到研究组的参与者，他们要么失访，要么在 HIV 感染前停止参与。
四项试验共纳入并随机分配了 7367 名女性；本分析包括 7086 名参与者。1514 名（21.4％）参与者失访或提前终止。在最终的 Cox 模型中，以下基线因素与失访相关：年龄较小（危险比 [HR] = 0.95）；受教育程度较低（HR = 0.97）；上次性行为时使用避孕套（HR = 1.18）；典型周内的性活动次数较多（HR = 1.01）；基线念珠菌病或细菌性阴道病（HR = 1.12）。
在这些杀微生物剂试验中，较年轻和受教育程度较低的女性更难以保留。但这些相同的特征可能与更高的 HIV 感染率相关。针对那些失访和可能感染风险较高的女性，采取强化保留方法将优化研究效率和有效性。
