Sex Transm Dis. 2019 Jun;46(6):407-415. doi: 10.1097/OLQ.0000000000000978.
High attrition and irregular testing for human immunodeficiency virus (HIV) in cohort studies for high-risk populations can bias incidence estimates. We compare incidence trends for high-risk women attending a dedicated HIV prevention and treatment clinic, using common methods for assigning when seroconversion occurs and whether seroconversion occurs among those with attrition.
Between April 2008 and May 2009, women were enrolled into cohort 1 and from January 2013 into cohort 2, then scheduled for follow-up once every 3 months. Incidence trends based on assuming a midpoint in the seroconversion interval were compared with those of assigning a random-point. We also compared estimates based on the random-point with and without multiple imputation (MI) of serostatuses for participants with attrition.
By May 2017, 3084 HIV-negative women had been enrolled with 18,364 clinic visits. Before attrition, 27.6% (6990 of 25,354) were missed visits. By August 2017, 65.8% (426 of 647) of those enrolled in cohort 1 and 49.0% (1194 of 2437) in cohort 2 were defined with attrition. Among women with 1 or more follow-up visit, 93 of 605 in cohort 1 and 77 of 1601 in cohort 2 seroconverted. Periods with longer seroconversion intervals appeared to have noticeable differences in incidences when comparing the midpoint and random-point values. The MI for attrition is likely to have overestimated incidence after escalated attrition of participants. Based on random-point without MI for attrition, incidence at end of observation was 3.8/100 person-years in cohort 1 and 1.8/100 in cohort 2.
The random-point approach attenuated variation in incidence observed using midpoint. The high incidence after years of ongoing prevention efforts in this vulnerable population should be investigated to further reduce incidence.
在高危人群的队列研究中，由于艾滋病毒（HIV）的高淘汰率和不规则检测，可能会使发病率估计值产生偏差。我们比较了在专门的艾滋病毒预防和治疗诊所就诊的高危女性的发病率趋势，使用了在确定血清转换发生时间和淘汰者中是否发生血清转换时的常用方法。
2008 年 4 月至 2009 年 5 月，女性被纳入队列 1，2013 年 1 月纳入队列 2，然后每 3 个月随访一次。基于假设血清转换间隔中点的发病率趋势与随机点的发病率趋势进行了比较。我们还比较了基于随机点的估计值，以及是否对淘汰者的血清状态进行了多次插补（MI）。
截至 2017 年 5 月，3084 名 HIV 阴性女性已入组，共进行了 18364 次就诊。在淘汰前，25354 次就诊中有 27.6%（6990 次）为漏诊。截至 2017 年 8 月，队列 1 中 65.8%（426 名）和队列 2 中 49.0%（1194 名）的入组者被定义为淘汰者。在有 1 次或多次随访就诊的女性中，队列 1 中有 93 名和队列 2 中有 77 名发生了血清转换。当比较中点值和随机点值时，血清转换间隔较长的时期似乎在发病率上存在明显差异。对于淘汰者的 MI 可能高估了淘汰者增加后的发病率。基于随机点且不考虑淘汰者的 MI，队列 1 的终点观察发病率为 3.8/100 人年，队列 2 为 1.8/100。
随机点方法减轻了使用中点时观察到的发病率变化。在这个弱势群体中，经过多年持续的预防努力，发病率仍然很高，应该对此进行调查，以进一步降低发病率。
