Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO, United States of America.
PLoS One. 2020 Aug 13;15(8):e0237580. doi: 10.1371/journal.pone.0237580. eCollection 2020.
HIV screening (i.e. antigen/antibody) tests are followed by a supplemental (i.e. antibody-only) if the screen is positive. Discrepant results can result from two scenarios: a false-positive screening test or acute HIV infection. These scenarios can be distinguished by a molecular HIV test, but due to contamination concerns, our laboratory recently implemented a policy requiring a second specimen dedicated for molecular HIV testing. Our objective was to (1) characterize the effect of this policy on the time-to-diagnosis for patients with discrepant screening and supplemental test results, and (2) explore "strength of positivity" as an interim predictor of screening test accuracy while awaiting confirmatory test results.
Data from our laboratory information system, electronic health record, and instrument logs were used to collate data for all HIV testing performed at Barnes-Jewish Hospital (BJH) between January 1, 2014 and October 18, 2017.
Requiring a dedicated specimen for molecular testing significantly increased the time-to-diagnosis for patients with discrepant screening and supplemental HIV tests (p = 0.0084). This policy also contributed to loss-to-followup, with 0/35 discrepant cases lost-to-followup prior to policy implementation compared to 2/10 after implementation. However, by optimizing the signal-to-cutoff (S/CO) ratio of the screening test, we were able to more accurately distinguish false-positives from acute-HIV prior to molecular testing (sensitivity of 100%, specificity of 89%).
We propose utilizing quantitative fourth-generation assay results (S/CO) ratios as a predictor of infection true positivity in situations where the screening assay is reactive but the supplemental test is negative and confirmatory molecular results are not immediately available.
如果初筛（即抗原/抗体）结果阳性，则需要进行补充（即仅抗体）检测。不一致的结果可能来自两种情况：假阳性初筛试验或急性 HIV 感染。这些情况可以通过分子 HIV 检测来区分，但由于污染问题，我们实验室最近实施了一项政策，要求专门采集第二份标本进行分子 HIV 检测。我们的目的是：（1）描述该政策对初筛和补充检测结果不一致的患者的诊断时间的影响；（2）在等待确认性检测结果时，探索“阳性强度”作为初筛检测准确性的临时预测指标。
使用实验室信息系统、电子健康记录和仪器日志中的数据，整理了 2014 年 1 月 1 日至 2017 年 10 月 18 日期间在 Barnes-Jewish 医院（BJH）进行的所有 HIV 检测的数据。
要求专门采集标本进行分子检测显著增加了初筛和补充 HIV 检测不一致患者的诊断时间（p = 0.0084）。该政策还导致失访增加，实施前有 0/35 例初筛和补充检测不一致的患者失访，而实施后有 2/10 例失访。然而，通过优化初筛试验的信号/截止值（S/CO）比值，我们能够在进行分子检测之前更准确地区分假阳性和急性 HIV（敏感性为 100%，特异性为 89%）。
我们建议在初筛试验呈阳性而补充试验呈阴性且无法立即获得确认性分子结果的情况下，利用第四代定量检测的结果（S/CO）比值作为感染真实性的预测指标。
