Background and purpose: Surrogate markers such as viral load are necessary to follow the evolution of disease resulting from infection with Human Papilloma virus (HPV), especially in this era of vaccination. As such, this paper uses the automated system Cobas-4800-HPV to define viral load as number of HPV copies/cell and apply the results to clinical samples.
Study design: A curve to determine viral load per cell was constructed from HPV plasmid and cell concentrations using the Cobas-4800-HPV system. According to these curves, HPV viral load was determined in 309 positive endocervical swabs (58 from patients with previous HPV-infection, 118 with current lesions and 133 symptom-free patients presenting for screening) from women attending gynaecology consultations from January to June 2013.
Results: In curves with r(2)≥0.95 the Cobas-4800-HPV system has a detection limit of 150 (2.18 log) viral copies, and the limit for β-globin corresponds to that of a single cell. In women reporting for screening, viral load was under 10(4) (4 log) copies/10(3) cells. For women with lesions or previous HPV infection loads were significantly higher particularly in the 30-45 year group (p=0.038). Elevated viral loads were especially noticeable in non-HPV 16/HPV 18.
Conclusions: Automated system Cobas-4800-HPV is suitable for define viral load of HPV. Correlation between viral load and number of cells established. Higher viral load in women with disease, and those between 30 and 45 years. Increased viral load of non-16/18 high-risk HPV genotypes detected in patients with lesions compared to screening patients. A difference not observed for HPV 16/18, or in coinfections.
Keywords: HPV; Intraepithelial lesion; Neoplasic progression; Viral load.
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