Comparison of real-time PCR with conventional bDNA based assay for quantification of HBV, HCV and HIV-1: possible clinical implications
Abstract number: 1733_678
Amendola A., Solmone M., Garbuglia A., Angeletti C., Lauria N., Capobianchi M.
Objectives: We compared two commercial assays [Versant 3.0, System 340 (Bayer Diagnostics), based on branched DNA technology, and COBAS Ampliprep TaqMan, CAP-TCM (Roche Diagnostics), based on real-time PCR] in measuring HBV, HCV and HIV viraemia.
Methods: 150 consecutive serum samples from patients with chronic hepatitis B (divided in HBeAg-positive or Anti-HBeAb-positive), 92 clinical samples from patients eligible to HCV therapy and 46 clinical samples from HIV-seropositive individuals have been analysed. Moreover, commercially available standard panels of HBV, HCV and HIV-1 were used to compare the linearity of two assays.
Results: In the overlapping range, an elevated degree of correlation between the tests was measured for all viruses concentrations:
HBV: r = 0.9389, p < 0.001;
all HCV genotypes: r = 0.7702, p < 0.001. HCV genotypes 14: r = 0.721, p < 0.001; r = 0.753, p < 0.001; r = 0.0.873, p < 0.001; and r = 0.783, p < 0.001, respectively;
HIV-1: r = 0.9885, p < 0.0001.
The analysis of mean values indicated that HBV DNA values obtained with bDNA-based assay were higher than those obtained with TaqMan. On the contrary, HCV and HIV-1 viral load values obtained in CAP/CTM were generally higher than those obtained in bDNA. Comparisons conducted according to Bland and Altman method showed that differences of measurement occurred at higher magnitude of viral load. Moreover, for all viruses analysed, a considerable proportion of clinical samples gave results discordant by more than 0.5 or even 1 log that seemed not genotype-dependent.
Conclusion: These results suggest that quantitative results obtained by different assays may not be interchangeable, even though expressed in the same (international) units. In general, CAP/CTM shows higher sensitivity and broad linear range, but at high magnitudo of viral load HBV-DNA was under estimated while HCV and HIV-1 were over estimated.
Therefore, it is recommendable that the same quantitative assay be used longitudinally in monitoring therapeutic response of individual patients. Longitudinal studies are necessary to evaluate the impact of the higher viral load results obtained in the real time PCR-based tests in clinical decision-making.
|Session name:||European Society of Clinical Microbiology and Infectious Diseases|
|Location:||ICC, Munich, Germany|
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