HBV-RNA Co-amplification May Influence HBV DNA Viral Load Determination.

Despite effective hepatitis B virus (HBV)-DNA suppression, HBV RNA can circulate in patients receiving nucleoside/nucleotide analogues (NAs). Current assays quantify HBV DNA by either real-time polymerase chain reaction (PCR), which uses DNA polymerase, or transcription-mediated amplification, which uses reverse-transcriptase (RT) and RNA polymerase. We assessed the effect of RT capability on HBV-DNA quantification in samples from three cohorts, including patients with quantified HBV RNA. We compared the HBV-DNA levels by real-time PCR (cobas HBV, Roche 6800/8800; Xpert HBV, Cepheid), transcription-mediated amplification (Aptima HBV, Hologic), and real-time PCR with added RT capability (cobas HBV+RT). In the first cohort (n = 45) followed over 192 weeks of NA therapy, on-treatment HBV-DNA levels were higher with cobas HBV+RT than cobas HBV (mean difference: 0.14 log10 IU/mL). In a second cohort (n = 50) followed over 96 weeks of NA therapy, HBV-DNA viral load was significantly higher with the cobas HBV+RT and Aptima HBV compared with the cobas HBV test at all time points after initiation of NA therapy (mean difference: 0.65-1.16 log10 IU/mL). A clinically significant difference was not detected between the assays at baseline. In a third cohort (n = 53), after a median of 2.2 years of NA therapy, we detected HBV RNA (median 5.6 log10 copies/mL) in 23 patients (43.4%). Median HBV-DNA levels by Aptima HBV were 2.4 versus less than 1 log10 IU/mL in samples with HBV RNA and without HBV RNA, respectively (P = 0.0006). In treated patients with HBV RNA, Aptima HBV measured higher HBV-DNA levels than Xpert HBV and cobas HBV. Conclusion: Tests including an RT step may overestimate HBV DNA, particularly in samples with low viral loads as a result of NA therapy. This overestimation is likely due to amplification of HBV RNA and may have an impact on clinical decisions.

High-volume workflow and performance comparisons for Chlamydia trachomatis and Neisseria gonorrhoeae testing using automated molecular platforms.

BACKGROUND: The global burden of sexually transmitted infections (STIs) is high and there have been reports of increasing chlamydial and gonorrheal infections. High-volume screening programs for Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) are an important component of STI control. This study evaluated the high-volume workflow and performance of the cobas® CT/NG assay for use on the automated Roche cobas® 6800 system, with the cobas p 480 instrument for pre-analytics, compared with the Aptima Combo 2 assay on the Hologic Panther system. METHODS: High-volume workflow and performance were evaluated using paired female urine specimens. Workflow analysis (n = 376) included hands-on time (HoT), number of manual interventions, and time to first and last results. For performance assessment, paired results from the cobas CT/NG and Aptima Combo 2 assays, for both CT and NG, were compared and two-sided 95% confidence intervals calculated to provide estimates of positive percent agreement (PPA), negative percent agreement (NPA), and overall percent agreement (OPA) between the tests. McNemar's test was used for significance testing. RESULTS: Pre-analytical preparations and system start-up on the cobas 6800 system required 00:27:38 (hr:min:sec) HoT whilst the Panther system required 00:30:43. The cobas 6800 system required eight interactions and 00:43:59 HoT to process 376 samples. The Panther system required six interactions and 00:39:10 HoT. Time to first results was 02:53:00 on the cobas c6800 system for 96 samples and 03:28:29 on the Panther system for five samples. The cobas 6800 system delivered all 376 results 3 h faster than the Panther system (07:45:26 and 10:47:30, respectively). The performance correlation between both assays was high (PPA, NPA and OPA > 99% for both CT and NG). McNemar's test revealed no statistically significant difference between the assays. CONCLUSION: For high-volume automated CT/NG testing, both the cobas 6800 system and Panther system provided accurate results. Although less manual intervention steps were needed for the Panther system, improved turnaround time was obtained with the cobas 6800 system with less risk for contamination. The additional testing capacity on the cobas 6800 system would allow a growing service to deliver more results in a single shift.

Generating timely molecular diagnostic test results: workflow comparison of the cobas® 6800/8800 to Panther.

Background: Molecular diagnostic tests for HBV, HCV and HIV-1 and other pathogens are widely used for clinical management. Practical issues related to workflow and labor requirements need to be characterized to inform selection of the most appropriate system. Research design and methods: We compared the workflow of two high-throughput systems: cobas 6800 (Roche) and Panther (Hologic), using average mid-size laboratory test volumes for five different assays (HIV-1, HBV, HCV, HPV or TV, and CT/NG). Results: Set-up time, time to first results, time to last results, and total hands-on time for cobas 6800 was 0.40, 2.47, 7.12, and 0.98 hours, respectively; on the Panther system, these times were 0.75, 2.7, 9.1, and 1.48 hours. Fifty-seven samples had results available at the first time point on cobas 6800 compared to 5 samples on the Panther system. The Panther system required more manual steps including several with potential risks of contamination or error. The number of reagents items required was 5 for cobas 6800 and 40 for the Panther system. Conclusions: Both systems provided a high level of automation. The cobas 6800 platform had shorter start up, time to first result, time to last result and hands-on times than the Panther system.

Analytical performance of four molecular platforms used for HIV-1, HBV and HCV viral load determinations.

Background: Viral load (VL) quantification is important for the management of HBV, HCV, and HIV-1-infected patients. Several semi- or fully automated systems and assays are available that can be used to measure VL for these and other targets. Research design and methods: We assessed the accuracy, genotype/subtype inclusivity, and precision of four VL assays for three viral targets: cobas 4800 (Roche), cobas 6800 (Roche), Aptima (Hologic) and VERIS (Beckman), using WHO standards, cell culture supernatants and clinical samples. Results: Most results were close to expected values, except for significant under-quantification of HIV-1 group O, HBV genotype C, and D at high VL, and HCV genotype 3 by Aptima, and of HIV-1 CRF01_AE and group N and HCV genotype 3 by VERIS. Precision was comparable between tests except for VERIS HCV, which showed more variability. Aptima and cobas 6800 results agreed well with each other except HBV VL at lower VL (<10,000 IU/mL) where Aptima results tended to be higher. Conclusions: Results from different VL assays may not always agree in certain subsets of patients. Clinicians should we aware of these findings when making treatment decisions.