Parkin Neil T
Data First Consulting, Belmont, California, USA.
AIDS Rev. 2014 Jul-Sep;16(3):160-71.
World Health Organization-recommended surveys of acquired HIV-1 drug resistance include assessment of HIV-1 viral load suppression to levels below 1,000 copies/ml and drug resistance-associated mutation patterns in subjects on antiretroviral therapy. Surveys are being conducted in regions of the world that cannot support the collection, storage, and shipping of frozen plasma. Therefore, dried blood spots are often the specimen type of choice for both genotyping and viral load measurement. Furthermore, viral load testing for individual patient management in these regions is being scaled-up in accordance with WHO 2013 Guidelines for Antiretroviral Treatment. Technical issues related to the adaptation of viral load assays to dried blood spots, especially with respect to sensitivity (limit of detection), specificity (cell-free RNA vs. cell-associated DNA or RNA), and assay method, affect the interpretation of a viral load result from dried blood spots. Amongst published studies of commercial assay performance with dried blood spots, the bioMérieux EasyQ® and Abbott RealTime assays tended to show high (> 90%) specificity and sensitivity; the Biocentric Generic or Roche TaqMan® assays tended to show high sensitivity but lower specificity, using a 1,000 copies/ml threshold. The relative contribution of cell-associated DNA or RNA to a viral load measurement is likely to vary between patients, depending on clinical parameters and treatment status. A model was developed that predicts that in patients on antiretroviral therapy with low plasma viral load, cellular DNA is the predominant source of non-plasma virus-derived nucleic acid in dried blood spots. The extent of viral load overestimation from dried blood spots becomes less important when plasma viral load is over about 5,000 copies/ml. To avoid misclassifying subjects with plasma viral load suppression, the World Health Organization-recommended threshold of 1,000 copies/ml can be applied only when an assay that can distinguish between DNA and RNA is used (e.g. bioMérieux EasyQ® or Abbott RealTime). There is a need for additional affordable technologies with the ability to discriminate between cell-free (plasma) and cell-associated nucleic acids.
世界卫生组织推荐的获得性HIV-1耐药性调查包括评估HIV-1病毒载量抑制到低于1000拷贝/毫升的水平，以及对抗逆转录病毒治疗患者的耐药相关突变模式进行评估。调查正在世界上无法支持冷冻血浆采集、储存和运输的地区开展。因此，干血斑通常是基因分型和病毒载量检测的首选标本类型。此外，根据世界卫生组织《2013年抗逆转录病毒治疗指南》，这些地区针对个体患者管理的病毒载量检测正在逐步扩大。与病毒载量检测方法适应干血斑相关的技术问题，特别是在灵敏度（检测限）、特异性（游离RNA与细胞相关DNA或RNA）和检测方法方面，会影响对干血斑病毒载量结果的解读。在已发表的关于干血斑商业检测性能的研究中，生物梅里埃公司的EasyQ®和雅培实时检测往往显示出高（>90%）特异性和灵敏度；使用1000拷贝/毫升阈值时，Biocentric通用检测或罗氏TaqMan®检测往往显示出高灵敏度但特异性较低。细胞相关DNA或RNA对病毒载量检测的相对贡献可能因患者而异，这取决于临床参数和治疗状态。开发了一个模型，预测在血浆病毒载量较低的抗逆转录病毒治疗患者中，细胞DNA是干血斑中非血浆病毒来源核酸的主要来源。当血浆病毒载量超过约5000拷贝/毫升时，干血斑导致的病毒载量高估程度变得不那么重要。为避免对血浆病毒载量得到抑制的受试者进行错误分类，只有在使用能够区分DNA和RNA的检测方法（如生物梅里埃公司的EasyQ®或雅培实时检测）时，才能应用世界卫生组织推荐的1000拷贝/毫升阈值。需要有更多能够区分游离（血浆）和细胞相关核酸的经济实惠的技术。
