Table 1.

The seroprevalence of syphilis in Chengdu blood center, 2005–2017

	2005	2006	2007	2008	2009	2010	2011	2012	2013	2014	2015	2016	2017
Total number of blood donations	92610	105949	121745	137524	150702	145691	149863	153299	160507	182222	192959	205963	219140
Number of initial blood donors	82304	86948	93272	104551	110174	102357	120561	134350	128455	116679	117722	122212	124779
Number of repeat donors	10306	19001	28473	32973	40528	43334	29302	18949	32052	65543	75237	83751	94361
Total number of syphilis-positive	815	804	889	1019	1302	1486	1452	1825	2280	1869	1709	2052	2157
syphilis-positive in the initial blood donors.	734	712	796	938	1119	1245	1241	1541	1869	1621	1516	1795	1828
syphilis-positive in repeat donors	81	92	93	81	183	241	211	284	411	248	193	257	329
Rate of TP-Positive(%)	0.88	0.76	0.73	0.74	0.86	1.02	0.97	1.19	1.42	1.02	0.89	1.00	0.98
Seroprevalence(%)	0.89	0.82	0.85	0.90	1.02	1.22	1.03	1.15	1.46	1.39	1.29	1.47	1.46
serological incidence (%)	0.79	0.48	0.33	0.25	0.45	0.56	0.72	1.50	1.28	0.38	0.26	0.31	0.35
P value	0.282	<0.001	<0.001	<0.001	<0.001	<0.001	<0.001	<0.001	0.021	<0.001	<0.001	<0.001	<0.001

Seroprevalence(%): the seroprevalence was calculated using the total number of syphilis-positive donors as the numerator in the initial blood donation, the total number of initial blood donors at the same period as the denominator. Serological incidence(%): The total number of syphilis-positive in the repeat blood donors in that year was the numerator, all repeat blood donors during the same period was the denominator