JOURNAL ARTICLE

Concordance Rates of Adolescent Idiopathic Scoliosis in a Danish Twin Population

Ane Simony, Leah Y Carreon, Karen Hjmark, Kirsten O Kyvik, Mikkel Ø Andersen
Spine 2016 October 1, 41 (19): 1503-7
27163371

STUDY DESIGN: Clinical, radiological, and genetic determination of zygosity of twin pairs from the Danish Twin Registry who self-reported having adolescent idiopathic scoliosis (AIS).

OBJECTIVE: To establish concordance rates of AIS.

SUMMARY OF BACKGROUND DATA: The etiology of and the true mode of inheritance of AIS remain unclear. Studies on concordance in twin pairs provide a basis for analyzing the influence of genetic versus environmental factors. In 2007, using self-report of AIS from the Danish Twin Registry, concordance rates of 0.13 in monozygotic twins and 0.00 in dizygotic twins were reported.

METHODS: All 46,418 twins registered in the Danish Twin Registry born from 1931 to 1982 were sent a survey, which included questions about scoliosis. The survey was returned by 34,944 individuals (75.3%) representing 23,204 pairs. From the present study, 548 individuals representing 274 complete twin pairs in which at least one twin self-reported having scoliosis were invited to a clinical and radiological examination. Zygosity was established by genetic testing.

RESULTS: A total of 182 individuals (33.2%) of the original cohort agreed to participate, 128 of whom had scoliosis by self-report. There were 91 twin pairs, in which one or both twins had reported scoliosis and 36 individuals whose twin did not want to participate. Only 35 (27%) of the 128 participants with self-reported scoliosis had a clinically and radiologically confirmed curve. Calculating concordance in twins with Cobb angles greater than 10°, we found that the pairwise concordance rate was 0.4 (0.10-0.70) for monozygotic and 0.05 (-0.05-0.15) for dizygotic twins, P = 0.05, probandwise concordance was 0.45 (0.16-0.74) for monozygotic and 0.1 (-0.03-0.23) for dizygotic pairs.

CONCLUSION: Concordance rates in a Danish twin population using genetic testing for zygosity are higher than previously reported using self-report. Although not statistically significant, the differences in monozygotic and dizygotic pairs indicate that genetic factors may be of importance for scoliosis.

LEVEL OF EVIDENCE: 3.

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