Table 2. The HPV positive rates in the follow-up for different periods from the first HPV positive.

Persistent period	Positive number	Total number	Positive rate (95% CI)	P
One year	186	218	85.3 (79.9–89.7)	<0.001
Two years	73	118	61.9 (52.5–70.6)
Three years	73	118	61.9 (52.5–70.6)

Notes.

The persistence rate of HPV infection was calculated as (①+ and ②+)/(①+ and ②+/-) for one year persistence, (①+ and ②+ and ③+)/(①+ and ②+/- and ③+/-) for two-year persistence and (①+ and ②+ and ③+ and ④+)/(①+ and ②+/- and ③+/- and ③ +/-) for three-year persistence, where ①, ②, ③, and ④ mean the detection at the first, second, third and fourth year, respectively, and + means HPV positive, and +/- means HPV positive or negative.