Author: Catlett B, Bajis S, Starr M, Dore GJ, Cunningham PH, Hajarizadeh B , Grebely J, Applegate TL

Theme: Epidemiology & Public Health Research Year: 2019

Background: Simplified HCV diagnostic strategies to increase testing and linkage to care are needed.
Novel collection methods such as finger-stick capillary dried blood spots (DBS) have advantages over
standard phlebotomy, especially among people who inject drugs where venous access may be a
barrier to testing. The aim of this study was to evaluate the diagnostic performance of the Hologic
Aptima HCV Quant assay for the detection and quantification of HCV RNA with finger-stick capillary
DBS and venepuncture samples.
Methods: Plasma and finger-stick capillary DBS samples were collected from participants in an
observational cohort enrolled at six sites in Australia (four drug treatment clinics, one homelessness
service and one needle and syringe programme). We compared the sensitivity, specificity, bias and
agreement of the Aptima HCV assay for HCV RNA detection by finger-stick capillary DBS with
venepuncture (gold standard). Retesting was performed on samples that had undetectable HCV RNA
in plasma and detectable/unquantifiable HCV RNA (<10 IU/mL) in DBS. Results: Of 175 participants enrolled in December 2016, 164 participants (11 participants on DAA therapy were excluded) had paired viral load results. HCV RNA was detected in 45 (27%) of 164 participants based on the Aptima assay in plasma. Among 38 people with undetectable HCV RNA in plasma and detectable/unquantifiable HCV RNA (<10 IU/mL) in DBS, 32 samples were available for re-testing (all HCV undetectable). Sensitivity for HCV RNA detection in DBS was 95.6% (95% CI 84.9- 99.5%) and specificity was 94.1% (95% CI 88.3-97.6%). Sensitivity for HCV RNA quantification in DBS (≥10 IU/mL in plasma) was 100% (95% CI 91.8% to 100%) and specificity was 100% (95% CI 97% to 100%). Finally, a small bias of 0.37 Log10 in plasma over DBS (95% CI 0.78-1.55) was observed with good agreement (R2=0.96). Conclusion: The Aptima HCV Quant assay can detect active infection from DBS with acceptable diagnostic performance and is clinically comparable to plasma. Repeat testing of HCV RNA detectable/unquantifiable samples suggest that a quantifiable result is a more reliable indicator for active infection. Disclosure of Interest Statement: The views expressed in this publication do not necessarily represent the position of the Australian government. Hologic provided Aptima HCV Dx reagents. The Kirby Institute is funded by the Australian Government Department of Health and Ageing and the National Health and Medical Research Program Grant (#1053206). B.C and SB are supported by an Australian Postgraduate Award from the University of New South Wales (UNSW) Sydney and an Australian Government Research Training Program Scholarship. J.G is supported by a National Health and Medical Research Council Career Development Fellowship. T.A has received travel grants and travel support from Abbott Diagnostics and travel grants from Cepheid. J.G is a consultant/advisor and has received research grants from AbbVie, Bristol-Myers Squibb, Cepheid, Gilead Sciences and Merck/MSD.

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