Chinese National Twin Registry

Outline

Chinese National Twin Registry is the first and largest population-based twin registry in China. It was established in 2001. The primary goal of this program is the establishment of a population-based twin registry of 45,000 twin pairs from several regions representing north, south, urban, and rural areas in China. A secondary goal is to study genetic contributions to complex diseases, and to test associations of candidate genes with related phenotypes. Eight thousand two hundred and ninety-one twin pairs have been enrolled in the registry, in which 1613 pairs have undergone detailed questionnaire assessments and physical examination. Based on the baseline registry, a twin cohort was established. Continued research includes studies on intermediate phenotypes of cardiovascular and cerebrovascular diseases and psychological studies in adult twins, studies on growth and development in adolescent twins, and so forth. The current state and future plans for the Chinese National Twin Registry will be discussed in this chapter.

The Chinese National Twin Registry (CNTR), established with the financial support of the China Medical Board, New York (CMB01-746) in 2001, is the first population-based twin registry in China. Chinese twins are invited to join this voluntary registry regardless of zygosity type, age, health or medical history. In the early days of its establishment, this program focused on genetic epidemiological studies of cardiovascular and cerebrovascular diseases. Since its expansion, the CNTR provides in addition an important resource for researchers across a broad range of disciplines.

The primary goal of the CNTR is the establishment of a population-based twin registry of 45,000 twin pairs from several regions representing north, south, urban, and rural areas in China. Beijing, Qingdao, Shanghai and Lishui were selected as representative regions. A secondary goal is the study of genetic contributions to complex diseases, and the testing of associations of candidate genes for these disease phenotypes. The establishment of the CNTR and all genetic epidemiological study protocols were reviewed and approved by the Ethics Committee for Human Subject Studies of the Peking University Health Science Center.

1. Recruitment of Twins in the CNTR

The CNTR is a voluntary registry. Twins were recruited through the following: residence registry in the public security bureaus, public media, local health care networks and neighborhood/village committees (Yang et al., 2002). The registration of twins was achieved mainly through the three-tiered prevention and health system (village, township and county level) in China. However, for twins who underwent detailed assessment, certain recruitment methods played a more predominant role than others in particular locations. For example, in Qingdao, twins were recruited mainly through the newspaper, TV and neighbourhood/village committees, while in Lishui twins were recruited mainly through local general practitioners in the health care system. Only twins where both twins were alive and living in the twin registry coverage
area were included in the registry.

The CNTR is administered through the Department of Epidemiology and Biostatistics, School of Public Health, Peking University. The data and samples of twins were collected and reported by local Centers for Disease Control and Prevention (CDCs). The database of the CNTR uses Epidata as the interface.

2. Various Registries in the CNTR

By the end of June 2007, the field work of the CNTR had been carried out in Beijing, Shanghai, Qingdao and Lishui, which resulted in the enrollment of 8291 twin pairs in total (Figure 16.1). These 8291 twin pairs included 5895 pairs who were registered in the Qingdao registry between 2001 and 2004, 787 pairs who underwent simple assessment in the Beijing registry in 2004, 741 pairs who underwent detailed assessment in the Lishui registry between 2002 and 2005, and 868 pairs who underwent simple assessment in the Shanghai registry in 2006. The age and sex distributions of the registered twins in Qingdao, Beijing, Shanghai and Lishui are listed in Tables 16.1, 16.2, 16.3, and 16.4 respectively.

Figure 16.1 Twin pairs registered in China

3. Scientific Research

3.1 Detailed assessment

In the CNTR, a total of 1613 twin pairs in Qingdao and Lishui were administered an interview questionnaire (zygosity determination, medical history, smoking and drinking, medical history of their linear relatives, etc) and physical examination (height, weight, blood pressure, waist, hip and pulse). To determine concentrations of some biochemical indices (Table 16.5 for detail) and to keep DNA, a fasting blood sample was collected from each participant after written informed consent was obtained. For adolescents, their sitting height, circumference of chest, shoulder width, pelvis width, and skin fold were also measured to reflect their growth status.

Table 16.1 The Age and Sex Distribution of Registered Twins in Qingdao

Birth year	Twins (Pairs)			Triplet+	Total
Birth year	Male	Female	Mixed	Triplet+	Total
<1929	11	5	2	0	18
1930-39	13	7	6	0	26
1940-49	33	12	10	0	55
1950-59	119	40	40	0	199
1960-69	253	136	112	3	504
1970-79	339	279	157	4	779
1980-89	440	436	246	11	1133
1990-99	921	805	472	17	2215
2000-	436	339	181	10	966
Total	2565	2059	1226	45	5895

Table 16.2 The Age and Sex Distribution of Registered Twins in Beijing

Birth year	Twins (Pairs)			Triplet+	Total
Birth year	Male	Female	Mixed	Triplet+	Total
1930-39	1	0	0	0	1
1940-49	2	1	0	0	3
1950-59	10	4	1	0	15
1960-69	22	19	11	0	52
1970-79	32	21	16	0	69
1980-89	77	74	50	0	201
1990-99	106	109	74	2	291
2000-	55	68	31	1	155
Total	305	296	183	3	787

Table 16.3 The Age and Sex Distribution of Registered Twins in Shanghai

Birth year	Twins (Pairs)			Triplet+	Total
Birth year	Male	Female	Mixed	Triplet+	Total
1930-39	0	0	2	0	2
1940-49	8	4	5	0	17
1950-59	30	14	9	0	53
1960-69	83	50	26	1	160
1970-79	66	49	31	2	148
1980-89	76	88	37	1	202
1990-99	80	76	22	3	181
2000-	46	43	16	0	105
Total	389	324	148	7	868

Table 16.5 Biochemical Items Measured in Lishui and Qingdao

	Lishui	Qingdao
ABO blood type	[check mark]	[check mark]
Rh blood type		[check mark]
HBsAg	[check mark]	[check mark]
Fasting blood glucose	[check mark]	[check mark]
CHOL	[check mark]	[check mark]
TG	[check mark]	[check mark]
HDL-C	[check mark]	[check mark]
LDL-C	[check mark]	[check mark]
Apo A1	[check mark]
Apo B	[check mark]
LPL (a)	[check mark]
ALT	[check mark]	[check mark]
CR	[check mark]	[check mark]
UA	[check mark]	[check mark]
BUN	[check mark]	[check mark]
K	[check mark]	[check mark]
Na	[check mark]	[check mark]
Regular blood test		[check mark]
Regular uric test^*		[check mark]
Other biochemical items^↑		[check mark]
^*Regular uric test: NIT, PH, GLU, PRO, BLD, KET, BIL, URO. ^↑Other biochemical items: TBIL, DBIL, IBIL, D/I, AST, S/L, AKP, GGT, TP, ALB, GLB, A/G, PA, TBA, CHE, LDH, Cl, Ca, Mg, P, CO2CP, AG, CP, TRF.