We report the process of adaptation into Sinhala of a questionnaire given to mothers of twins to determine zygosity. Adaptation and validation was carried out in three stages. Firstly, we used a nominal group to translate the English version and to assess the extent of agreement (consensus measurement) on the appropriateness of the translation and resolve disagreement (consensus development). Secondly we used a qualitative interview with 25 mothers of twins. The three main stems of the translated questionnaire were used as a semi-structured interview, and the responses noted verbatim. These were categorised and analysed, and the translated full questionnaire was then presented as closed questions with fixed choice responses. The categorised responses generated during the qualitative interview were compared with the responses to the fixed choices in the full questionnaire. The third stage was the appraisal of the questionnaire by 17 bilingual parents of twins. The source and translated version of the questionnaire were given to them at least 3 days apart. The responses were rated and the total scores were computed to determine the zygosity. This step was carried out to measure the validity and reliability of the Sinhala version. A perfect correlation between the original and adapted version was obtained, with a kappa of 1. The results suggest that the Sinhala version of the questionnaire is conceptually equivalent to the original questionnaire. Comparison of the zygosity determination by using this adapted questionnaire with results from analysis of genetic markers on Sri Lankan twins is needed for final validation of the translated questionnaire. Twin Research (2000) 3, 205–212.
Nearly all twin registers are based in developed countries and there is no twin register in the developing world. Our objectives were to initiate the process of establishing a nationwide twin register in Sri Lanka by starting a volunteer register first and working towards a population-based register. Regular newspaper advertisements, feature articles, radio talks, and television programmes were used to publicise a competition for twins, their parents/relatives and friends requesting them to participate by sending in details of twins. The competition ran from 28 March 1997 for a period of 3 months. It offered prizes for three winners selected by drawing lots. Advertisements highlighted the objective of the competition as establishing a twin register for future research and emphasised that informed consent would be obtained for individual research projects. Those who registered comprise 4602 twin pairs (same sex: male – 1564, female – 1885; different sex – 1153), 80 sets of triplets (same sex: male – 17, female – 31; different sex – 42) and two sets of quadruplets (different sex). The oldest twins, triplets, quadruplets are 85, 46, and 5 years old, respectively; 88.0% of twins are less than 30 years old. Although others have previously used media publicity to enrol twins in twin registers, we believe this to be the first time that twins have been enrolled through competition. We have more young twins, and our gender and zygosity proportions after applying Weinburg’s rule do not match the proportions expected from a volunteer twin sample. Establishing a twin register for research purposes has proved possible in a developing country. Twin Research (2000) 3, 202–204.
