Accurate HIV viral load measurement in primary health care settings using the cobas® plasma separation card

Abstract

Introduction 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. Methodology 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. Results 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

Stability of HIV-1 Nucleic Acids in cobas Plasma Separation Card for Viral Load Measurement

“…The misclassification rate for this study was 0.7% in capillary PSC specimens and 0.3% in venous PSC specimens. 12 …”

“…Nevertheless, the cobas PSC specimen has been shown to be suitable to identify virologic failure and treatment success at this clinically relevant threshold. 12 The stability of PSC specimens stored at high temperatures for up to 28 days is an important feature for field conditions in resource-limited settings, given that in most sub-Saharan African countries, preshipment storage at health facilities and transportation of specimens to the reference laboratories can take up to a month. 16 …”

“…After collection and drying, the specimen on the card can be packed and transported to a laboratory for HIV-1 VL testing. 12 , 13 …”

“…Recently, the cobas plasma separation card (PSC) was shown to be a more accurate alternative to DBSs. 12 , 13 Despite this recent evidence of the good performance of the PSC for HIV-1 VL testing, it is unknown whether HIV-1 RNA in the PSC remains stable when exposed to higher temperatures in the tropics. These data are important for the establishment of functional referral systems in sub-Saharan Africa, given the variability of temperature during transportation from clinics to the testing laboratory.…”

Managing laboratory waste from HIV-related molecular testing: Lessons learned from African countries

“…In addition, there is a lack of knowledge and/or capacity to systematically quantify the amount of waste generated from VL and EID testing facilities, including liquid chemical waste. Deducing from the estimates by Sleeman et al (2018) , the VL tests would translate to approximately 35,000 kg, 56,000 kg and 84,000 kg of solid waste and 15,000 L, 25,000 L and 37,000 L liquid chemical waste per annum in Malawi, Mozambique and Zimbabwe, respectively ( Nyagadza et al, 2019 ; Ehrenkranz et al, 2019 ; Vubil et al, 2020 ). The amount of waste will increase with additional molecular COVID-19 diagnostic tests, which also contain GTC as testing is scaled-up in response to the pandemic.…”