Reducing Read Time of Point-of-Care Test Does Not Affect Detection of Hepatitis C Virus and Reduces Need for Reflex RNA
Authors: David Smookler, Aaron Vanderhoff, Mia J. Biondi, Jorge Valencia, Pablo Ryan, Joel Karkada, Rachel Hong, Izza Sattar, Erin Mandel, Martina Gjevori, Julia Casey, David Fletcher, Hemant Shah, Bettina E. Hansen, Camelia Capraru, Harry L.A. Janssen, Jeffrey V. Lazarus, Jordan J. Feld
Journal: Clinical Gastroenterology and Hepatology (2020)

Background & AimsGlobal elimination of hepatitis C virus (HCV) will require increases in diagnosis. Point of care (POC) tests that detect antibodies against HCV can be useful for testing large and difficult to reach populations. The most accurate POC test requires a 20 min read time to identify antibody-positive samples. We investigated whether viremic patients could be identified using a shorter read time, to increase efficiency and reduce the need for reflex tests (a follow-up test for HCV RNA on the same specimen to confirm viremia).MethodsPatients with past or current HCV infections provided samples at 2 clinics in Canada for evaluation by the OraQuick HCV Rapid antibody POC test. A community HCV-screening program in Madrid, Spain (real-world cohort) invited people to be tested for HCV with the same OraQuick test. Patients provided samples of whole blood, via finger prick. Fingerprick samples were tested immediately after collection. In the clinic cohort, photographs of the developing test were taken at 15 second intervals, and blinded readers recorded the time to positivity. In the real-world cohort, readers recorded the OraQuick result at 5 minutes, and each minute after, up to 10 minutes, and then again at 20 minutes; viremia was then evaluated using a POC HCV RNA test (GeneXpert HCV Viral Load Assay). Sera from viremic and non-viremic clinic patients were used to quantify antibody titers to investigate the relationship between the time of band appearance and antibody concentration. Fisher's exact test and exact logistic regression were used to determine factors associated with a positive result at 5 minutes.ResultsBlood from all viremic patients produced a positive result in the antibody POC test by 5 min. Median time to a positive result for 171 viremic patients was 2.6 min (range, 1.8–4.6 min), vs 4.1 min (range, 2.3–14.4 min) for 108 patients with resolved infection (P < .001). The 5-min threshold identified all viremic cases among 176 HCV antibody–positive patients in the real-world cohort, confirmed by testing for HCV RNA. In the pooled cohorts, antibody positivity at 5 min identified viremic patients with 100% sensitivity (95% CI, 98.4%–100%); the negative predictive value was 100% (95% CI, 94.9%–100%). The positive predictive value at 5 min was 62.0% (95% CI, 56.7%–67.0%) and therefore insufficient alone to detect viremia; an HCV RNA test would still be necessary to confirm active infection.ConclusionsThe wait time for the OraQuick HCV Rapid antibody POC blood test can be reduced from 20 min to 5 min and continue to reliably identify patients with HCV infection. Shortening the test time could increase high-throughput screening, reduce loss to follow up, and reduce the need for reflex HCV RNA testing. Global elimination of hepatitis C virus (HCV) will require increases in diagnosis. Point of care (POC) tests that detect antibodies against HCV can be useful for testing large and difficult to reach populations. The most accurate POC test requires a 20 min read time to identify antibody-positive samples. We investigated whether viremic patients could be identified using a shorter read time, to increase efficiency and reduce the need for reflex tests (a follow-up test for HCV RNA on the same specimen to confirm viremia). Patients with past or current HCV infections provided samples at 2 clinics in Canada for evaluation by the OraQuick HCV Rapid antibody POC test. A community HCV-screening program in Madrid, Spain (real-world cohort) invited people to be tested for HCV with the same OraQuick test. Patients provided samples of whole blood, via finger prick. Fingerprick samples were tested immediately after collection. In the clinic cohort, photographs of the developing test were taken at 15 second intervals, and blinded readers recorded the time to positivity. In the real-world cohort, readers recorded the OraQuick result at 5 minutes, and each minute after, up to 10 minutes, and then again at 20 minutes; viremia was then evaluated using a POC HCV RNA test (GeneXpert HCV Viral Load Assay). Sera from viremic and non-viremic clinic patients were used to quantify antibody titers to investigate the relationship between the time of band appearance and antibody concentration. Fisher's exact test and exact logistic regression were used to determine factors associated with a positive result at 5 minutes. Blood from all viremic patients produced a positive result in the antibody POC test by 5 min. Median time to a positive result for 171 viremic patients was 2.6 min (range, 1.8–4.6 min), vs 4.1 min (range, 2.3–14.4 min) for 108 patients with resolved infection (P < .001). The 5-min threshold identified all viremic cases among 176 HCV antibody–positive patients in the real-world cohort, confirmed by testing for HCV RNA. In the pooled cohorts, antibody positivity at 5 min identified viremic patients with 100% sensitivity (95% CI, 98.4%–100%); the negative predictive value was 100% (95% CI, 94.9%–100%). The positive predictive value at 5 min was 62.0% (95% CI, 56.7%–67.0%) and therefore insufficient alone to detect viremia; an HCV RNA test would still be necessary to confirm active infection. The wait time for the OraQuick HCV Rapid antibody POC blood test can be reduced from 20 min to 5 min and continue to reliably identify patients with HCV infection. Shortening the test time could increase high-throughput screening, reduce loss to follow up, and reduce the need for reflex HCV RNA testing.