OBJECTIVETo determine the association between viral load of high risk human papillomavirus (HR-HPV) and cervical intraepithelial neoplasia (CIN).

METHODSCervical exfoliated cells were collected from 18 186 women aged 17 -59 from six urban areas and eight rural areas when they were screened in the cross-sectional population-based studies from 1999 to 2008. HR-HPV was detected by the Hybrid Capture 2 (hc2) system, and viral load was measured by the ratio of relative light units to standard positive control (RLU/PC). RLU/PC was categorized for analysis into four groups: negative [0, 1.00), low viral load [1.0, 10.00), moderate viral load [10.00, 100.00), and high viral load > or = 100.00. Cervical lesions were diagnosed by biopsies as normal, CIN 1, CIN 2, CIN 3 and squamous cervical cancer (SCC). Association between HR-HPV viral load and CIN was evaluated by unconditional multinomial logistic regression.

RESULTSThe HR-HPV infection rate of the population was 14.51% (2515/17334). 100.00% (29/29) of SCC, 97.63% (206/211) of CIN 3, 93.43% (199/213) of CIN 2, 75.04% (421/561) of CIN 1 and 10.17% (1660/16320) of normal women were positive for HR-HPV DNA. The median RLUs for the HR-HPV positive women with SCC, CIN 3, CIN 2, CIN 1 and normal were 320.85, 158.05, 143.70, 125.34 and 9.64, respectively. There were significant differences among the distributions of viral loads in each lesion (chi2 = 6190.40, P < 0.01). The severity of CIN increased with the viral load (chi2 = 5493.35, P <0.01). Compared with the risks of CINs in HR-HPV negative population, the risks of CINs in low, moderate and high viral loads were increased gradually [OR(95% CI) : CIN 1 : 9.01(6.31 - 12.87), 24.96(18.23 - 34.17) and 68.42(51.40 - 91.08); CIN 2 : 26.44(12.07 - 57.95), 98.53(49.54 - 195.98) and 322.88(168.62 - 618.27); CIN 3+ : 72.89(24.02-221.18); 343.58(121.81-969.09) and >999.99(473.38 - >999.99)], and there were obvious dose-response relationships (chi2trend was 3115.05, 2413.95 and 3098.57, respectively. P< 0.01). In each age group of the HR-HPV positive population,the risks of CIN 2 + in the women with moderate or high viral load were higher than the one with low viral load [OR(95% CI): <35 : 4.71(1.23 - 18.09) and 15.06(4.40 - 51.49); 35 -: 4.01 (1.62 -9.90) and 14.09(6.15 -32.28); 40 - : 3.06(1.52 -6.16) and 7.78(4.05 -14.95); > or =45: 3.50(1.36 -9. 01) and 7.57(3.13 - 18. 30)], and there was a positive correlation between the risk of CIN 2+ and the viral load (chi2trend was 51.33, 66.28, 53.64 and 51.00, respectively. P <0.01). The risk of CIN 2 + was highest among the women aged 40 - with high viral load [OR (95% CI) : 2.02 (1.15 - 3.52)].

CONCLUSIONThere is strong correlation between the HR-HPV viral load and the severity of CIN, and so is the correlation between the HR-HPV viral load and the risk of CIN 2 +. A moderate to high viral load of HR-HPV should be the major risk factor for the cervical cancer and CIN 2 and CIN 3, and there is a higher risk in the women aged 35 or older than the younger ones. Considering both the age and viral load could help the doctors to manage the screening women more effectively.