Estimating Twin Pair Concordance for Age of Onset
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Twin and family data provide a key source for evaluating inheritance of specific diseases. A standard analysis of such data typically involves the computation of prevalences and different concordance measures such as the casewise concordance, that is the probability that one twin has the disease given that the co-twin has the disease. Most diseases have a varying age-of-onset that will lead to age-specific prevalence. Typically, this aspect is not considered, and this may lead to severe bias as well as make it very unclear exactly what population quantities that we are estimating. In addition, one will typically need to deal with censoring in the data, that is the fact that we for some subjects only know that they are alive at a specific age without having the disease. These subjects needs to be considered age specifically, and clearly if they are young there is still a risk that they will develop the disease. The aim of this contribution is to show that the standard casewise concordance and standard prevalence estimators do not work in general for age-of-onset data. We show how one can in fact do something easy and simple even with censored data. The key is to take age into account when analysing such data.
KeywordsAge of onset Casewise concordance function Concordance function Cumulative incidence probability Prostate cancer Recurrence risk ratio
We are truly grateful to two referees and the editor for their careful reading of our manuscript and their very useful suggestions.
Conflict of Interest
Thomas H. Scheike, Jacob B. Hjelmborg and Klaus K. Holst declare that they have no conflict of interest.
Human and Animal Rights and Informed Consent
The paper only works on data collected by Danish twin registry that complies with the rules of Human and Animal rights.
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