Human Papillomavirus (HPV) Type 16 and Type 18 DNA Loads at Baseline and Persistence of Type-Specific Infection during a 2-Year Follow-Up

Background. Studies of viral load-associated persistence of human papillomavirus (HPV) infection are rare, with inconsistent results reported. Methods. The study subjects were 741 and 289 women who were positive for HPV type 16 (HPV-16) and HPV type 18 (HPV-18), respectively, at the time of enrollment into in the ASCUS-LSIL ( Atypical Squamous Cells of Undetermined Significance-Low-Grade Squamous Intraepithelial Lesion) Triage Study and who returned 1 or more times for HPV testing during a biannual 2-year follow-up. The numbers of HPV-16 and HPV-18 copies per nanogram of cellular DNA at baseline were measured by use of real-time polymerase chain reaction. Results. Women with, compared with women without, persistent infection at month 6 of follow-up had a higher viral load at enrollment (P < .001, for HPV-16; P = .01, for HPV-18). The association of each 1-log(10) increase in viral load with persistence of HPV-16 or HPV-18 during the first 6 months of the study was statistically significant among women with multiple HPV types at enrollment ( for HPV-16: odds ratio [ OR], 1.53 [ 95% confidence interval {CI}, 1.29-1.82]; for HPV-18: OR, 1.35 [ 95% CI, 1.09-1.68]) but not among women with monotype infections ( in tests assessing the interaction between viral load and coinfection, P = .002 for HPV-16 and P = .34 for HPV-18). Among women who continued to have positive results at month 6, 12, or 18, persistence of infection for another 6 months was unassociated with the viral load at baseline. Conclusion. Prevalent infection with a higher viral load of HPV-16 or HPV-18 was associated with short-but not long-term persistence.