title: Challenges in recruiting older twins for the Sri Lankan twin registry.
abstract: The National Twin Registry of Sri Lanka was established in 1997 as a volunteer register. To extend it to a population-based 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 20700 birth records. The twinning rate was estimated at 29.95 ([620/20700] x 1000) twins per 1000 registered births (CI 27.63-32.27). 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.
authors.affiliation: Section of Epidemiology, Institute of Psychiatry, Kings College, University of London, UK. spjuats@iop.kcl.ac.uk
authors.forename: Athula
authors.initials: A
authors.lastname: Sumathipala
authors.forename: Sisira H
authors.initials: SH
authors.lastname: Siribaddana
authors.forename: Nihal M R
authors.initials: NM
authors.lastname: Abeysingha
authors.forename: Nimali
authors.initials: N
authors.lastname: De Silva
authors.forename: Devaka J S
authors.initials: DJ
authors.lastname: Fernando
authors.forename: D A R K
authors.initials: DA
authors.lastname: Dayaratne
authors.forename: Deepthi
authors.initials: D
authors.lastname: De Silva
authors.forename: Narada D
authors.initials: ND
authors.lastname: Warnasuriya
authors.forename: Mathew
authors.initials: M
authors.lastname: Hotopf
mesh_terms: D001719:Birth Certificates; D006801:Humans; D012042:Registries; D013188:Sri Lanka; D011795:Surveys and Questionnaires; D014427:Twins