Intraclass Correlation Coefficient

Philip Sedgwick
Reader in medical statistics and medical education
Centre for Medical and Healthcare Education, St George’s, University of London, London, UK

January 7, 2015

Researchers investigated the association between bone mineral density measurements in twins, with monozygotic (identical) and dizygotic (non-identical) twins studied separately. The comparison was part of a study that investigated the association between vitamin D receptor genotype and bone mineral density in postmenopausal twins. A cross sectional study design was used, with participants recruited from a national register of twins in Britain. Participants were 87 monozygotic and 95 dizygotic pairs of twins aged 50-69 years, postmenopausal, and free of diseases affecting bone.

The main outcome measures included lumbar spine bone mineral density as measured by dual energy x ray absorptiometry. The intraclass correlation coefficient for lumbar spine bone mineral density between monozygotic twins was higher than for dizygotic ones (0.74 v 0.36). It was concluded that in British postmenopausal women’s lumbar spine bone mineral density was genetically linked.

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Cite this as: BMJ 2013;346:f1816

This post is based on an article published in "Endgames" an educational series from The BMJ. Other Endgames articles are available here. Copyright BMJ Publishing Group 2013.