Instituto Nacional de Saúde, Marracuene, Mozambique.
Clinton Health Access Initiative, Maputo, Mozambique.
PLoS One. 2020 May 6;15(5):e0232122. doi: 10.1371/journal.pone.0232122. eCollection 2020.
Plasma is considered the gold standard for HIV viral load (VL) testing, however its use is challenging due to the need for phlebotomy and centrifugation services, as well as cold chain for transporting to laboratories for testing. The use of Dried Blood Spot (DBS) specimen has allowed a rapid expansion of antiretroviral therapy (ART) monitoring in remote areas in many African countries, however, the VL in DBS may overestimate the copies of viral RNA result at the clinically relevant range of 1000 copies/ml, due to proviral DNA and intracellular RNA. The characteristics of the cobas® Plasma Separation Card (PSC) specimen are similar to fresh plasma (gold standard), so a better performance of HIV VL is expetected in PSC specimen and can be an alternative to DBS. This study aims to evaluate the performance of cobas® PSC for VL testing at primary health care facilities in Mozambique.
HIV-1 infected adults on ART were enrolled consecutively in two health facilities in Mozambique, between August 2018 and October 2018. Capillary and venous cobas® PSC, DBS and fresh plasma specimens were collected from each patient. All specimens were tested for VL using CAP/CTM v2.0. Sensitivity and specificity of viral load using DBS, capillary and venous PSC specimens were estimated. Viral load obtained in fresh plasma specimen was used as reference and a threshold of 1000 copies/ml was considered for the analyses.
From the total 613 patients included for the study, 2444 specimens including DBS (613), plasma (613), venous cobas® PSC (609) and capillary cobas® PSC (609) were collected and 2407 results were obtained. Sensitivity and specificity of the VL using venous cobas®PSC specimen at 1000 copies/ml threshold were 99.8% and 98.1% respectively, whereas for capillary cobas® PSC sensitivity was 99.6% and specificity was 97.2%. For DBS VL, sensitivity was 96.9% and specificity was 81.8%. Misclassification rate was more prominent in DBS specimens (5.9%), but lower in venous and capillary cobas®PSC with a rate of 0.3% and 0.7% respectively.
The cobas® PSC specimen has improved performance over DBS for more accurate VL testing aligned with plasma testing. The use of this specimen type can increase the rates of reliable VL results and this will improve the quality of VL monitoring of HIV-positive patients in low-income settings.
血浆被认为是 HIV 病毒载量 (VL) 检测的金标准，然而，由于需要进行静脉穿刺和离心服务，以及需要冷链运输到实验室进行检测，因此其使用具有挑战性。使用干血斑 (DBS) 标本允许在许多非洲国家的偏远地区快速扩展抗逆转录病毒治疗 (ART) 监测，然而，由于前病毒 DNA 和细胞内 RNA，DBS 中的 VL 可能会高估临床相关范围内 1000 拷贝/ml 的病毒 RNA 结果的拷贝数。cobas® 血浆分离卡 (PSC) 标本的特性与新鲜血浆 (金标准) 相似，因此 cobas® PSC 标本中的 HIV VL 表现更好，可作为 DBS 的替代品。本研究旨在评估 cobas® PSC 在莫桑比克基层医疗设施中进行 VL 检测的性能。
2018 年 8 月至 2018 年 10 月期间，在莫桑比克的两个卫生机构连续纳入接受 ART 治疗的 HIV-1 感染成人患者。从每位患者采集毛细管和静脉 cobas® PSC、DBS 和新鲜血浆标本。所有标本均采用 CAP/CTM v2.0 检测 VL。估计使用 DBS、毛细管和静脉 cobas® PSC 标本进行病毒载量的灵敏度和特异性。以新鲜血浆标本中的病毒载量作为参考，并将 1000 拷贝/ml 作为分析的阈值。
在总共纳入研究的 613 名患者中，共采集了包括 DBS(613)、血浆(613)、静脉 cobas®PSC(609)和毛细管 cobas®PSC(609)在内的 2444 份标本，获得了 2407 份结果。当以 1000 拷贝/ml 的阈值使用静脉 cobas®PSC 标本进行 VL 检测时，灵敏度和特异性分别为 99.8%和 98.1%，而毛细管 cobas®PSC 的灵敏度为 99.6%，特异性为 97.2%。对于 DBS VL，灵敏度为 96.9%，特异性为 81.8%。DBS 标本的错误分类率更高（5.9%），而静脉和毛细管 cobas®PSC 的错误分类率较低，分别为 0.3%和 0.7%。
与血浆检测相比，cobas® PSC 标本在更准确的 VL 检测方面优于 DBS，使用这种标本类型可以提高可靠 VL 结果的比例，从而提高低收入环境中 HIV 阳性患者的 VL 监测质量。
