This urban Sri Lankan population of subjects with T2DM demonstrated a compromised periodontal status compared with non-diabetic controls.

No abstract

T he National Twin Registry of Sri Lanka was established in 1997 as a volunteer register. To extend it to a populationbased register, we examined the effectiveness of tracing older twins by inspecting birth records and recruiting them by postal invitation and in-person contact. Birth records at a divisional secretariat reported from 2 maternity hospitals between the years of 1954-1970 were scrutinised to identify a random sample of twins. These hospitals had the highest twin delivery rates for the whole country. We identified 620 twins and a questionnaire was mailed to them. Research assistants visited a cohort of non-respondents (71) in the postal survey. These 620 twins were identified after perusing 20,700 birth records. The twinning rate was estimated at 29.95 ([620/20700] × 1000) twins per 1000 registered births ). In the postal survey, 37 (12%) responded and 62 letters were returned (20%). Both twins were still alive in 20 pairs, one was still alive in 15 pairs, and both twins were dead in 2 pairs. During field visits, 42 (59.2%) addresses were located. Information was available on 16 twin pairs. Both twins were alive in 8 pairs, one each in 4 pairs, and both were dead in 4 pairs and at least one twin was traced in 10 pairs (14%). Both the postal and the field survey gave a low yield. This finding is different from tracing younger twins born between 1985-1997 by using the same methods. Migration, urbanization and development in the country might have affected tracing older twins from the birth record addresses, which were decades old.

Sri Lanka is an island with genetic diversity between the five main population groups. Our twin registry is the first in the developing world. Initially, we established a volunteer cohort of 4600 twin pairs through a competition advertised in the media. In addition, we have volunteer cohorts, birth registration-based cohorts through hospitals, and community-based cohorts. There is also a nationwide population-based younger twin cohort (1992-1997) traced through the Department of Birth and Death Registration. Additionally, we have adapted a Zygosity determination questionnaire and validated it. Establishing ethical guidelines for twin research was a priority because the field of bio-ethics is at an early stage of development in Sri Lanka. These guidelines were from a developing world perspective. A sister organization, the Multiple Birth Foundation, was formed to cater to twins and their special needs and to represent their interests, and several branches have been formed. We intend to build capacity by establishing a genetic lab and through crosscultural collaboration. Our vision is to establish a multidisciplinary research foundation. Based on our research findings, we plan to build services to cater to needs of twins by working with professionals, statutory services and government policy makers.

Identifying twins for a population-based register can be achieved through birth records or community surveys. We studied the feasibility and effectiveness of different methods of identifying and recruiting twins to establish a population based register. To trace twins a population survey was carried out using an interviewer administered questionnaire. We also inspected the birth registration certificates at a divisional secretariat reported from a specified hospital between the years of 1985–1997 and compared it to the birth register of this same hospital. To recruit twins a random sample of 75 twin pairs (150 twins) identified at the Divisional Secretariat were contacted through the post and 25 twin pairs (50 twins) were personally visited. The prevalence of twins was 6.5 twins per 1000 people in the area surveyed. The twinning rate at the hospital was 18.92 twins per 1000 births. A discrepancy of 38 multiples births between the hospital labour room records and those registered at the DS was noted. The response from the postal invitation for recruitment was 59% and the response from the personal invitation was 68%. (Difference 9.4% 95% CI; 7.06–11.73). Community survey and systematic inspection of birth records either at the hospital or the birth registration office was an effective method to trace twins. Once traced, personal contact was more effective than the postal invitation for recruitment of younger twins. A cost-effective approach would be to use a postal coverage followed by personal contact for non-responders. The alternative method, community coverage, would have financial implications.