Twin concordances test for ascertained trichotomous traits data

Abstract

In human genetics, twin studies are widely underwent for investigation of the genetic influence on diseases. There are several measures that had been proposed to evaluate the similarity between two twins for dichotomous traits when the twins are sampled at random. These measures include the correlations, odds ratios, and casewise and pairwise concordances. When data are sampled through an ascertainment procedure, truncated data are formed. Under this circumstance, odds ratio cannot be defined and correlations cannot be correctly estimated. However, concordance measures for dichotomous traits can still be estimated using the likelihood method. On the other hand, though theoretically concordance measures can be extended to trichotomous traits, how to define them and to derive their estimators for ascertained trichotomous traits data have not been thoroughly discussed. In this study, we aim to address several relevant issues for ascertained trichotomous traits data. We define two new (casewise and pairwise) concordance measures for trichotomous traits and demonstrate how to apply a so-called 'self-contained subsets method (SCSM)' to estimation of twin concordances for ascertained data. We show that this method can obtain the same estimates as the likelihood method in an easier way and derive the asymptotic variances of the SCSM estimates under ascertainment. We establish the testing procedure for test of the equality of concordance measures between monozygotic twin pairs and dizygotic twin pairs, and illustrate the methods with a real data set and conduct Monte Carlo simulation to investigate its power performance.

Likelihood‐based concordance tests for analysis of ascertained twin pair multinomial data

“…. Following the definition of  h for ascertained twin pair binomial data, analogously, an overall casewise/probandwise concordance (OCC)  h can be defined as [16]…”

“…If we assume a frequently used underlying Dirichlet-multinomial model for the type h twin pair data, the population frequencies of the joint disease states can be derived as (e.g. [11,16,28])…”

“…) or log‐linear models (e.g. ) and concordance measures (casewise or pairwise concordance) based on binomial or trinomial models .…”

“…) to analyze the ascertained twin pair continuous data with probands that have been selected because of deviant scores on a continuous variable. The frequently used similarity measures for analyzing the ascertained twin pair multinomial data are the casewise and pairwise concordances for ascertained twin pair binomial data , and the overall casewise concordance and overall pairwise concordance for ascertained twin pair trinomial data . Extending the analysis methods for the ascertained twin pair binomial data to those for the ascertained twin pair trinomial data is not so trivial.…”

Lack of association between the presence and persistence of betapapillomavirus DNA in eyebrow hairs and betapapillomavirus L1 antibodies in serum

“…It was interpreted similarly to a k statistic. The standard error and 95 % CI were estimated according to methods documented by Huang & Tai (2007). We estimated concordance separately for each bPV type and then calculated a pooled estimate across all types.…”