Cassim Naseem, Schnippel Kathryn, Coetzee Lindi Marie, Glencross Deborah Kim
National Health Laboratory Service (NHLS), National Priority Programmes, Johannesburg, South Africa.
Department of Molecular Medicine and Haematology, Faculty of Health Sciences, University of Witwatersrand, Johannesburg, South Africa.
PLoS One. 2017 Feb 6;12(2):e0171675. doi: 10.1371/journal.pone.0171675. eCollection 2017.
Cryptococcal meningitis is a major cause of mortality and morbidity in countries with high HIV prevalence, primarily affecting patients whose CD4 are < = 100 cells/μl. Routine Cryptococcal Antigen (CrAg) screening is thus recommended in the South African HIV treatment guidelines for all patients with CD4 counts < = 100 cells/μl, followed by pre-emptive anti-fungal therapy where CrAg results are positive. A laboratory-based reflexed CrAg screening approach, using a Lateral Flow Assay (LFA) on remnant EDTA CD4 blood samples, was piloted at three CD4 laboratories.
This study aimed to assess the cost-per-result of laboratory-based reflexed CrAg screening at one pilot CD4 referral laboratory.
CD4 test volumes from 2014 were extracted to estimate percentage of CD4 < = 100 cells/μl. Daily average volumes were derived, assuming 12 months per/year and 21.73 working days per/month. Costing analyses were undertaken using Microsoft Excel and Stata with a provider prospective. The cost-per-result was estimated using a bottom-up method, inclusive of test kits and consumables (reagents), laboratory equipment and technical effort costs. The ZAR/$ exchange of 14.696/$1 was used, where applicable. One-way sensitivity analyses on the cost-per-result were conducted for possible error rates (3%- 8%, reductions or increases in reagent costs as well as test volumes (ranging from -60% to +60%).
The pilot CD4 laboratory performed 267000 CD4 tests in 2014; ~ 9.3% (27500) reported CD4< = 100 cells/μl, equivalent to 106 CrAg tests performed daily. A batch of 30-tests could be performed in 1.6 hours, including preparation and analysis time. A cost-per-result of $4.28 was reported, with reagents contributing $3.11 (72.8%), while technical effort and laboratory equipment overheads contributed $1.17 (27.2%) and $0.03 (<1%) respectively. One-way sensitivity analyses including increasing or decreasing test volumes by 60% revealed a cost-per-result range of $3.84 to $6.03.
A cost-per-result of $4.28 was established in a typical CD4 service laboratory to enable local budgetary cost projections and programmatic cost-effectiveness modelling. Varying reagent costs linked to currency exchange and varying test volumes in different levels of service can lead to varying cost-per-test and technical effort to manage workload, with an inverse relationship of higher costs expected at lower volumes of tests.
隐球菌性脑膜炎是艾滋病毒高流行率国家死亡率和发病率的主要原因，主要影响CD4细胞计数≤100个/μl的患者。因此，南非艾滋病毒治疗指南建议对所有CD4细胞计数≤100个/μl的患者进行常规隐球菌抗原（CrAg）筛查，若CrAg检测结果为阳性，则进行先发制抗真菌治疗。在三个CD4检测实验室试点采用了基于实验室的反射性CrAg筛查方法，即使用侧向流动分析法（LFA）检测剩余的乙二胺四乙酸（EDTA）抗凝CD4血样。
本研究旨在评估一个试点CD4转诊实验室基于实验室的反射性CrAg筛查的每个检测结果成本。
提取2014年的CD4检测量，以估算CD4细胞计数≤100个/μl的比例。假设每年12个月、每月21.73个工作日，得出每日平均检测量。使用微软Excel和Stata软件进行成本分析，采用供应商前瞻性视角。采用自下而上的方法估算每个检测结果的成本，包括检测试剂盒和耗材（试剂）、实验室设备及技术人力成本。适用时使用14.696南非兰特/1美元的兰特/美元汇率。针对可能的错误率（3%-8%）、试剂成本的增减以及检测量（范围为-60%至+60%）对每个检测结果的成本进行单向敏感性分析。
该试点CD4实验室在2014年进行了267000次CD4检测；约9.3%（27500次）的检测结果显示CD4细胞计数≤100个/μl，相当于每天进行106次CrAg检测。一批30次检测可在1.6小时内完成，包括准备和分析时间。报告的每个检测结果成本为4.28美元，其中试剂成本为3.11美元（72.8%），技术人力成本为1.17美元（27.2%），实验室设备间接费用为0.03美元（<1%）。包括检测量增加或减少60%的单向敏感性分析显示，每个检测结果的成本范围为3.84美元至6.03美元。
在一个典型的CD4检测服务实验室确定了每个检测结果4.28美元的成本，以便进行当地预算成本预测和项目成本效益建模。与货币兑换相关的试剂成本变化以及不同服务水平下检测量的变化，可能导致每次检测成本和管理工作量的技术人力成本有所不同，预计检测量较低时成本会更高，二者呈反比关系。
