Fitzpatrick Christopher, Asiedu Kingsley, Sands Anita, Gonzalez Pena Tita, Marks Michael, Mitja Oriol, Meheus Filip, Van der Stuyft Patrick
Department of Control of Neglected Tropical Diseases, World Health Organization, Geneva, Switzerland.
Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, United States of America.
PLoS Negl Trop Dis. 2017 Oct 26;11(10):e0005985. doi: 10.1371/journal.pntd.0005985. eCollection 2017 Oct.
Yaws is a non-venereal treponemal infection caused by Treponema pallidum subspecies pertenue. The disease is targeted by WHO for eradication by 2020. Rapid diagnostic tests (RDTs) are envisaged for confirmation of clinical cases during treatment campaigns and for certification of the interruption of transmission. Yaws testing requires both treponemal (trep) and non-treponemal (non-trep) assays for diagnosis of current infection. We evaluate a sequential testing strategy (using a treponemal RDT before a trep/non-trep RDT) in terms of cost and cost-effectiveness, relative to a single-assay combined testing strategy (using the trep/non-trep RDT alone), for two use cases: individual diagnosis and community surveillance.
We use cohort decision analysis to examine the diagnostic and cost outcomes. We estimate cost and cost-effectiveness of the alternative testing strategies at different levels of prevalence of past/current infection and current infection under each use case. We take the perspective of the global yaws eradication programme. We calculate the total number of correct diagnoses for each strategy over a range of plausible prevalences. We employ probabilistic sensitivity analysis (PSA) to account for uncertainty and report 95% intervals.
At current prices of the treponemal and trep/non-trep RDTs, the sequential strategy is cost-saving for individual diagnosis at prevalence of past/current infection less than 85% (81-90); it is cost-saving for surveillance at less than 100%. The threshold price of the trep/non-trep RDT (below which the sequential strategy would no longer be cost-saving) is US$ 1.08 (1.02-1.14) for individual diagnosis at high prevalence of past/current infection (51%) and US$ 0.54 (0.52-0.56) for community surveillance at low prevalence (15%).
We find that the sequential strategy is cost-saving for both diagnosis and surveillance in most relevant settings. In the absence of evidence assessing relative performance (sensitivity and specificity), cost-effectiveness is uncertain. However, the conditions under which the combined test only strategy might be more cost-effective than the sequential strategy are limited. A cheaper trep/non-trep RDT is needed, costing no more than US$ 0.50-1.00, depending on the use case. Our results will help enhance the cost-effectiveness of yaws programmes in the 13 countries known to be currently endemic. It will also inform efforts in the much larger group of 71 countries with a history of yaws, many of which will have to undertake surveillance to confirm the interruption of transmission.
雅司病是由苍白密螺旋体地方亚种引起的一种非性病性螺旋体感染。世界卫生组织的目标是到2020年根除这种疾病。设想在治疗运动期间使用快速诊断检测（RDT）来确诊临床病例，并用于认证传播中断情况。雅司病检测需要同时进行螺旋体（trep）和非螺旋体（non-trep）检测以诊断当前感染。我们针对个体诊断和社区监测这两个用例，评估一种序贯检测策略（在trep/non-trep RDT之前使用螺旋体RDT）相对于单一检测组合策略（仅使用trep/non-trep RDT）的成本和成本效益。
我们使用队列决策分析来检查诊断和成本结果。我们估计在每个用例下，过去/当前感染和当前感染的不同流行率水平下替代检测策略的成本和成本效益。我们采用全球雅司病根除计划的视角。我们计算在一系列合理流行率范围内每种策略的正确诊断总数。我们采用概率敏感性分析（PSA）来考虑不确定性并报告95%区间。
按照目前螺旋体和trep/non-trep RDT的价格，序贯策略在过去/当前感染流行率低于85%（81 - 90）时用于个体诊断可节省成本；在低于100%时用于监测可节省成本。对于过去/当前感染高流行率（51%）下的个体诊断，trep/non-trep RDT的阈值价格（低于此价格序贯策略将不再节省成本）为1.08美元（1.02 - 1.14），对于低流行率（15%）下的社区监测为0.54美元（0.52 - 0.56）。
我们发现序贯策略在大多数相关情况下用于诊断和监测均可节省成本。在缺乏评估相对性能（敏感性和特异性）证据的情况下，成本效益是不确定的。然而，仅采用组合检测策略可能比序贯策略更具成本效益的情况有限。需要一种更便宜的trep/non-trep RDT，根据用例不同，成本不超过0.50 - 1.00美元。我们的结果将有助于提高已知目前流行雅司病的13个国家中雅司病项目的成本效益。这也将为71个有雅司病病史的更多国家的工作提供参考，其中许多国家将不得不进行监测以确认传播中断情况。
