When working with twins discordant for disease, a matched case–control study can be applied.
Twins are matched for:
- Genetic factors (perfectly for MZ pairs; 50% for DZ)
- Non-genetic familial factors (not necessarily to the same degree for MZ and DZ pairs)
- Mother, father, uterus and, perhaps, placenta
- Sex, if same-sex pairs
- Calendar year of birth
- Measured factors for which they are the same or similar
- Binary outcome
- Conditional logistic regression models
- These methods adjust for measured factors
- Matched for both measured and unmeasured factors
- Otherwise very similar to standard case–control studies
- Less costly and time-consuming than cohort studies
- Potential recall bias
- Inefficient for rare exposures
Cockburn, M., Black, W., McKelvey, W. and Mack, T. (2001). Determinants Of Melanoma In A Case-Control Study Of Twins (United States). Cancer causes & control, 12(7), 615-25.
Hamilton, A. S., & Mack, T.M. (2003). Puberty and genetic susceptibility to breast cancer in a case-control study in twins. The New England Journal of Medicine, 348(23), 2313-22.
Oliveira, V. C., Ferreira, M. L., Refshauge, K.M., Maher, C.G., Griffin, A.R., Hopper, J. L. and Ferreira, P. H. (2015). Risk factors for low back pain: insights from a novel case-control twin study. The Spine Journal, 15(1), 50-7.