Table 1. HPV-31 detection rate by Mass Spectrometry, demographic characteristics, behavior variables and proportion of positive specimens stratified by variant lineages in women from Northern China.
| Variables | Specimens from Northern China |
| MS Detection | |
| Specimens tested | 2703 |
| HPV-31 positive | 14 |
| HPV-31 detection rate (%) and 95%CI* | 0.52(0.28–0.87) |
| Education level | |
| Below junior middle school (%) | 9 (64.3) |
| Junior middle school or above (%) | 5 (35.7) |
| Age distribution | |
| Median (years) | 46 |
| Interquartile Range (years) | 40–56 |
| Number of sexual partners | |
| N< = 1 (%) | 14 (100) |
| N>1 (%) | 0 |
| Number of pregnancies | |
| < = 3 (%) | 8 (57.1) |
| >3 (%) | 6 (42.9) |
| Contraceptive usage | |
| Yes (%) | 1 (7.1) |
| No (%) | 13 (92.9) |
| Cigarette smoking | |
| Yes (%) | 1 (7.1) |
| No (%) | 13 (92.9) |
| Variant Lineage (N = 14) | |
| A variants (%) | 9 (64.3) |
| B variants (%) | 0 (0.0) |
| C variants (%) | 5 (35.7) |
*95% CI was calculated using Poisson distribution.