The costs of monitoring trachoma elimination: Impact, surveillance, and trachomatous trichiasis (TT)-only surveys

BackgroundAlthough trachoma causes more cases of preventable blindness than any other infectious disease, a combination of strategies is reducing its global prevalence. As a district moves toward eliminating trachoma as a public health problem, national programs conduct trachoma impact surveys (TIS) to assess whether to stop preventative interventions and trachoma surveillance surveys (TSS) to determine whether the prevalence of active trachoma has rebounded after interventions have halted. In some contexts, programs also conduct trachomatous trichiasis (TT)-only surveys. A few costing studies of trachoma prevalence surveys exist, but none examine TIS, TSS, or TT-only surveys.Methodology/Principal findingsWe assessed the incremental financial cost to the national program of TIS, TSS, and TT-only surveys, which are standardized cluster-sampled prevalence surveys. We conducted a retrospective review of expenditures and grant disbursements for TIS and TSS in 322 evaluation units in 11 countries between 2011 and 2018. We also assessed the costs of three pilot and five standard TT-only surveys in four countries between 2017 and 2018. The median cost of TIS and TSS was $8,298 per evaluation unit [interquartile range (IQR): $6,532–$10,111, 2017 USD]. Based on a linear regression with bootstrapped confidence intervals, after controlling for country, costs per survey did not change significantly over time but did decline by $83 per survey implemented in a single round (95% CI: -$108 –-$63). Of total costs, 80% went to survey fieldwork; of that, 58% went towards per diems and 38% towards travel. TT-only surveys cost a median of $9,707 (IQR: $8,537–$11,635); within a given country, they cost slightly more (106% [IQR: 94%–136%]) than TIS and TSS.Conclusions/SignificanceThe World Health Organization requires trachoma prevalence estimates for validating the elimination of trachoma as a public health problem. This study will help programs improve their planning as they assemble resources for that effort.

研究背景：尽管沙眼是引发可预防性失明病例最多的传染病，但多种综合防控策略正在逐步降低其全球患病率。当某一地区致力于消除沙眼这一公共卫生威胁时，国家项目会开展沙眼影响调查（Trachoma Impact Survey, TIS）以评估是否可终止预防性干预措施，同时开展沙眼监测调查（Trachoma Surveillance Survey, TSS）以判断干预措施停止后，活动性沙眼的患病率是否出现反弹。在部分实施场景中，项目还会开展仅针对沙眼性倒睫（Trachomatous Trichiasis, TT）的专项调查。目前已有少量针对沙眼患病率调查的成本核算研究，但尚无针对TIS、TSS或仅针对TT的专项调查的相关研究。

方法与主要研究结果：本研究针对国家项目开展的标准化整群抽样患病率调查——TIS、TSS以及仅针对TT的专项调查，评估了其所需的增量财政成本。我们回顾性分析了2011至2018年间，11个国家共322个评估单元的TIS与TSS相关支出及拨款拨付情况；同时评估了2017至2018年间，4个国家的3项试点及5项标准仅针对TT的专项调查的成本。TIS与TSS的中位成本为每个评估单元8298美元[四分位距（IQR）：6532~10111美元，以2017年美元计]。基于带有自举置信区间的线性回归分析，在控制国家变量后，单轮调查的单位成本未随时间发生显著变化，但每实施一次单轮调查，成本可降低83美元（95%置信区间：-108~-63美元）。在总成本中，80%用于调查实地工作；其中58%用于外勤津贴，38%用于差旅费。仅针对TT的专项调查中位成本为9707美元[四分位距（IQR）：8537~11635美元]；在同一国家内，其成本较TIS与TSS略高，为后者的106%[四分位距（IQR）：94%~136%]。

结论与意义：世界卫生组织要求通过沙眼患病率估算结果，验证沙眼作为公共卫生问题的消除状态。本研究将有助于相关项目在筹备资源以推进该目标时优化规划工作。