For infectious diseases, characterizing symptom duration is of clinical and public health importance. Symptom duration may be assessed by surveying infected individuals and querying symptom status at the time of survey response. For example, in a SARS-CoV-2 testing program at the University of Washington, participants were surveyed at least $28$ days after testing positive and asked to report current symptom status. This study design yielded current status data: outcome measurements for each respondent consisted only of the time of survey response and a binary indicator of whether symptoms had resolved by that time. Such study design benefits from limited risk of recall bias, but analyzing the resulting data necessitates tailored statistical tools. Here, we review methods for current status data and describe a novel application of modern nonparametric techniques to this setting. The proposed approach is valid under weaker assumptions compared to existing methods, allows use of flexible machine learning tools, and handles potential survey nonresponse. From the university study, under an assumption that the survey response time is conditionally independent of symptom resolution time within strata of measured covariates, we estimate that 19% of participants experienced ongoing symptoms 30 days after testing positive, decreasing to 7% at 90 days. We assess the sensitivity of these results to deviations from conditional independence, finding the estimates to be more sensitive to assumption violations at 30 days compared to 90 days. Female sex, fatigue during acute infection, and higher viral load were associated with slower symptom resolution.

翻译：对于传染病而言，表征症状持续时间具有临床和公共卫生意义。症状持续时间可通过调查感染者并询问其在应答调查时的症状状态来评估。例如，在华盛顿大学的一项SARS-CoV-2检测项目中，参与者在检测阳性后至少$28$天接受调查，并被要求报告当前症状状态。该研究设计产生了现时状态数据：每位受访者的结局测量仅包含调查应答时间以及截至该时间症状是否已缓解的二值指标。此类研究设计具有回忆偏倚风险较低的优势，但分析所得数据需要专门的统计工具。本文回顾了现时状态数据的分析方法，并描述了现代非参数技术在此场景中的创新应用。与现有方法相比，所提方法在更弱的假设下有效，允许使用灵活的机器学习工具，并能处理潜在的调查无应答问题。基于该大学研究，在假设调查应答时间与症状缓解时间在测量协变量分层内条件独立的前提下，我们估计有19%的参与者在检测阳性30天后仍存在持续症状，至90天时该比例降至7%。我们评估了这些结果对条件独立性假设偏离的敏感性，发现30天时的估计值比90天时的估计值对假设违反更为敏感。女性性别、急性感染期间的疲劳症状以及较高的病毒载量与症状缓解速度较慢相关。