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Web End = Behav Genet (2015) 45:573580 DOI 10.1007/s10519-015-9729-3

http://crossmark.crossref.org/dialog/?doi=10.1007/s10519-015-9729-3&domain=pdf

Web End = http://crossmark.crossref.org/dialog/?doi=10.1007/s10519-015-9729-3&domain=pdf

Web End = ORIGINAL RESEARCH

http://crossmark.crossref.org/dialog/?doi=10.1007/s10519-015-9729-3&domain=pdf

Web End = Estimating Twin Pair Concordance for Age of Onset

Thomas H. Scheike1 Jacob B. Hjelmborg2 Klaus K. Holst1

Received: 22 December 2014 / Accepted: 30 June 2015 / Published online: 15 July 2015 Springer Science+Business Media New York 2015

Abstract Twin and family data provide a key source for evaluating inheritance of specic 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 agespecic 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 specic age without having the disease. These subjects needs to be considered age specically, 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.

Keywords Age of onset Casewise concordance

function Concordance function Cumulative incidence

probability Prostate cancer Recurrence risk ratio

Introduction

In twin research a standard measure to describe the degree of association present within a twin-pair is the casewise concordance, that is the probability that both twins experience the disease of interest given that the co-twin has the disease. Several authors have discussed how to estimate this quantity, see for example Witte et al. (1999), Smith (1974), Hannah et al. (1985), Hannah et al....

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Estimating Twin Pair Concordance for Age of Onset

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