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HCV reflex testing: A single-sample, low-contamination method that improves the diagnostic efficiency of HCV testing
L Alexa Thompson1, Jayne Fenton2, Carmen L Charlton1,2,3
1Department of Laboratory Medicine and Pathology, University of Alberta, Edmonton, Alberta, Canada.
Background:
Hepatitis C virus (HCV) can be cured with antiviral treatments. Diagnosis normally requires two blood samples, one for serology screening and one for molecular confirmation. This multi-step process creates barriers in patient care and decreases testing for hard-to-reach populations. We used the cobas® 6800 to detect HCV RNA after antibody testing to investigate whether a single-sample reflex testing method is effective and efficient for diagnosing HCV-positive patients.
Methods:
HCV RNA-positive clinical samples (n = 152) were interchangeably loaded on the ARCHITECT i2000SR with negative samples (n = 152) in a checkerboard fashion, tested for HCV antibodies using fixed probes, and directly transferred to the cobas 6800 for molecular testing. Contamination rates, sensitivity, and specificity were determined by comparing Abbott m2000 and cobas 6800 viral loads. After implementing reflex testing, clinical data over a 6-month period were analyzed for diagnostic efficiency.
Results:
Contamination was present in 5 of 152 pairs (3.29%) after reflex testing. Sensitivity and specificity were 99.3% (95% CI 95.1% to 99.9%) and 100% (95% CI 97.5% to 100%), respectively, using the cobas 6800 assay after serotesting. Approximately 97% of clinical patients received a conclusive test result with the reflex-testing algorithm. For HCV-positive patients, mean diagnostic turnaround times were significantly lower using reflex testing versus the two-sample method (4 versus 39 days; p < 0.0001).
Conclusions:
HCV reflex testing demonstrated low levels of contamination without compromising the integrity of the molecular assay. Implementation in clinical laboratories would increase the efficiency of diagnosis and decrease steps in the continuum of care for patients.
