May 7, 2018 - Jason Grebely,* Gregory J. Dore,* and Tanya L. Applegate*. From the Kirby Institute,* University of New South Wales, Sydney, Australia; ...
The Journal of Molecular Diagnostics, Vol. 20, No. 5, September 2018
jmd.amjpathol.org
Evaluation of a Hepatitis C Virus Core Antigen Assay in Plasma and Dried Blood Spot Samples François M.J. Lamoury,* Behzad Hajarizadeh,* Angelica Soker,* Danica Martinez,* Camelia Quek,* Philip Cunningham,y Beth Catlett,y Gavin Cloherty,z Philippa Marks,* Janaki Amin,*x Jason Grebely,* Gregory J. Dore,* and Tanya L. Applegate* From the Kirby Institute,* University of New South Wales, Sydney, Australia; St. Vincent’s Applied Medical Research,y Sydney, Australia; and Abbott Diagnostics,z Abbott Park, Illinois; Faculty of Medicine and Health Sciences,x Macquarie University, Sydney, Australia Accepted for publication May 7, 2018. Address correspondence to Tanya L. Applegate, Ph.D., Viral Hepatitis Clinical Research Program, The Kirby Institute UNSW Sydney, Wallace Wurth Bldg., Sydney NSW 2052, Australia. E-mail: tapplegate@ kirby.unsw.edu.au.
Simplified, affordable tools to diagnose active hepatitis C virus (HCV) infection are needed to scale up treatment. This study evaluated the analytical performance of HCV core antigen (HCVcAg) detection in samples of plasma and dried venous blood spots (DBSs). Paired plasma and DBS samples were prepared from remnant diagnostic samples, and plasma HCV RNA and HCVcAg were quantified. Sensitivity and specificity for HCVcAg (>3 fmol/L) at two HCV RNA thresholds (15 and 3000 IU/mL) were calculated. Of 120 paired samples tested, 25 had nonquantifiable HCV RNA and 95 had quantifiable HCV RNA. The median HCV RNA level in plasma was 5.6 log10 IU/mL (interquartile range: 5.2 to 6.2). The median HCVcAg levels in plasma and DBS samples were 2.3 log10 fmol/L (interquartile range: 0.1 to 3.1) and 1.1 log10 fmol/L (interquartile range: 0.0 to 1.9), respectively. For diagnosing HCV RNA 3000 IU/mL, the sensitivity and specificity of HCVcAg in plasma were 97.7% (95% CI, 91%e100%) and 100% (95% CI, 87%e100%), respectively. The sensitivity and specificity of HCVcAg in DBS were 88.6% (95% CI, 80%e94%) and 97% (95% CI, 82%e 100%), respectively. The data from this study demonstrate good sensitivity and specificity of HCVcAg in plasma at an HCV RNA threshold of 3000 IU/mL. The level of HCVcAg quantified in plasma was higher than that in DBS. (J Mol Diagn 2018, 20: 621e627; https://doi.org/10.1016/j.jmoldx.2018.05.010)
Morbidity and mortality due to hepatitis C virus (HCV)related liver disease continues to increase globally, with an estimated 80 million individuals living with chronic HCV.1 Despite the arrival of highly effective direct-acting antiviral treatment regimens, hepatitis testing remains low and most individuals infected remain unaware of their infection.2 Even in high-income countries like the United States, 45% to 85% individuals are unaware of their HCV infection.3e5 Simple and affordable HCV testing methods for the detection of active infection are urgently required to identify those infected with HCV and to provide linkage to care.6,7 Standard diagnostic tests use either serologic assays to detect host response (antibodies to HCV) or nucleic acid testing (NAT) to detect the presence of the virus. NAT, which measures active infection, is the most sensitive and expensive diagnostic methodology. HCV core antigen (HCVcAg), a stable viral protein released during viral assembly, also detects active HCV infection. Other advantages of HCVcAg are a lower cost and a shorter assay time compared to NAT technologies.2 Previous studies have
shown that the analytical sensitivity of HCVcAg is inferior to that of NAT, but that the clinical sensitivity of the detection of chronic HCV is comparable between assays due to high plasma RNA level during chronic infection.8e10
Supported by Australian Government Department of Health and Ageing and the National Health and Medical Research Program grant 1053206 (G.J.D.), a National Health and Medical Research Council Career Development fellowship (J.G.), a National Health and Medical Research Council Practitioner Research fellowship (G.J.D.), and a National Health and Medical Research Council Early Career fellowship (B.H.). The Kirby Institute is funded by Australian Government Department of Health and Ageing and the National Health and Medical Research Program grant 1053206. Disclosures: G.J.D. is a consultant/advisor and has received research grants from AbbVie, Bristol-Myers Squibb, Gilead, Merck, Janssen, and Roche; J.G. is a consultant/advisor and has received research grants from AbbVie, Bristol-Myers Squibb, Cepheid, Gilead Sciences, and Merck/Merck Sharpe & Dohme; G.C. is an employee and shareholder of Abbott Laboratories; the kits of Architect HCV Ag were kindly provided by Abbott Laboratories; T.L.A has received research grants and travel support from Abbott Diagnostics. The views expressed in this publication do not necessarily represent the position of the Australian government.
Copyright ª 2018 American Society for Investigative Pathology and the Association for Molecular Pathology. Published by Elsevier Inc. All rights reserved. https://doi.org/10.1016/j.jmoldx.2018.05.010
Lamoury et al The World Health Organization recently released its first guidelines for hepatitis B and C testing, specifically recommending the use of dried blood spot (DBS) specimens as a tool to increase access to HCV testing.2 The collection of capillary whole blood by fingerstick as a DBS on filter paper greatly simplifies specimen collection, short-term storage on-site, and sample shipment at room temperature.9 In addition to being particularly well suited to low- and middle-income countries where direct access to HCV testing is limited, DBS may also help to reduce barriers in marginalized populations at high risk for HCV infection that do not have ready access to conventional health care in many settings, including those living in higher-income countries.11 For example, fingerstick sample collection is particularly helpful for individuals actively injecting drugs, in whom venous access can be extremely difficult.11e13 Further research is required to determine the analytical sensitivity of HCVcAg in DBS and to evaluate the potential use of this method for HCV diagnosis. This study determined the sensitivity and specificity of HCVcAg in a cohort of paired EDTA plasma and DBS remnant diagnostic samples.
Materials and Methods Study Participants Diagnostic samples received by SydPath, St. Vincent’s Hospital (Sydney, Australia) for standard-of-care HCV diagnostic testing were processed before routine testing. The use of those remnant samples was approved by the human research ethics committee at St. Vincent’s Hospital (LNR/ 12/SVH/358). Fifty microliters of whole venous blood was aliquoted onto Whatman 903 Protein Saver Cards (SigmaAldrich, Sydney, Australia), air-dried, and stored at 80 C for 1 to 3 years before testing. Remaining blood specimens were centrifuged at 1500 g for 20 minutes, and 2 mL of plasma was then aliquoted and stored at 80 C.
(Globe Scientific, Paramus, NJ) before loading. The Architect HCV Ag assay has a sensitivity of 3.00 fmol/L. Samples with concentration values of
