A computationally simple test of homogeneity of odds ratios for twin data

Abstract

It is of interest to compare measures of association of binary traits among samples of bivariate data. One example is the comparison of association within a sample of monozygotic (MZ) twins to that within a sample of dizygotic (DZ) twins. A larger association in the MZ twins suggests that the trait of interest may have a genetic component. The Bivariate data in this example are binary traits for the twins in each pair. Another example is the comparison of a measure of Hardy‐Weinberg disequilibrium across several populations. The bivariate data in this example are the two alleles comprising the genotype of interest. We propose using derived logistic regression equations from the full exponential model for the bivariate outcomes to test for homogeneity. We adjust for correlation among outcomes via generalized estimating equations. This modeling approach allows for adjustment for individual‐level and pair‐level covariates and thereby allows for testing for gene × environment interactions. Further, we extend the model to allow for simultaneous analysis of two diseases, which allows for testing for a genetic component to the coaggregation of two diseases. In contrast to approaches proposed by previous authors, no special software is required; our approach can be easily implemented in standard software packages. We compare our results to those of other methods proposed in the literature for data from the Vietnam Era Twins Study. We apply our methods also to the Anqing Twin Study and to data on major depression and generalized anxiety disorder from the Virginia Twin Register. Genet. Epidemiol. 20:228–238, 2001. © 2001 Wiley‐Liss, Inc.

Genetic Factors in Nickel Allergy Evaluated in a Population-Based Female Twin Sample

“…A large twin odds ratio may on the other hand be interpreted as an effect of genes or common environmental factors, whereas larger twin odds ratio among MZ twins than among DZ twins is interpreted as an effect of genes. Betensky et al (2001) describe how the twin odds ratio may be estimated in a simple manner by use of logistic regression of each twins nickel allergy status, conditioned on the co-twin's nickel allergy status. This method is based on a random sample of twins, and each pair is included twice in the analysis.…”

Genetic Factors in Nickel Allergy Evaluated in a Population-Based Female Twin Sample

“…A large twin odds ratio may on the other hand be interpreted as an effect of genes or common environmental factors, whereas larger twin odds ratio among MZ twins than among DZ twins is interpreted as an effect of genes. Betensky et al (2001) describe how the twin odds ratio may be estimated in a simple manner by use of logistic regression of each twins nickel allergy status, conditioned on the co-twin's nickel allergy status. This method is based on a random sample of twins, and each pair is included twice in the analysis.…”

Analysis of twin data ascertained through probands: The double‐entry approach

“…This measure of association is similar to the one proposed by Olson et al [1996]. In this parameterization, the model is identical to the one described by Betensky et al [2001]. The parameter p also describes, together with y 1i and y 2i , the marginal probability of being affected:…”

Associations of a novel IL4RA polymorphism, Ala57Thr, in Greenlander Inuit

“…This doubling of sample size was then corrected for by using robust variance estimates to allow for the duplication of the other within-person covariates in the same manner as previously described for use with twin data. 38 Multiple comparisons were not adjusted for because the analyses were based on an a priori hypothesis but were dealt with by describing all statistical analyses carried out. 39,40 All calculations were performed with the SPSS version 11.0 (SPSS Inc, Chicago, Ill) statistical package, except for the robust estimates, which were estimated with Stata software (StataCorp, College Station, Tex).…”

Genetic Factors in Nickel Allergy Evaluated in a Population-Based Female Twin Sample

“…A large twin odds ratio may on the other hand be interpreted as an effect of genes or common environmental factors, whereas larger twin odds ratio among MZ twins than among DZ twins is interpreted as an effect of genes. Betensky et al (2001) describe how the twin odds ratio may be estimated in a simple manner by use of logistic regression of each twins nickel allergy status, conditioned on the co-twin's nickel allergy status. This method is based on a random sample of twins, and each pair is included twice in the analysis.…”

Analysis of twin data ascertained through probands: The double‐entry approach

“…This measure of association is similar to the one proposed by Olson et al [1996]. In this parameterization, the model is identical to the one described by Betensky et al [2001]. The parameter p also describes, together with y 1i and y 2i , the marginal probability of being affected:…”

Associations of a novel IL4RA polymorphism, Ala57Thr, in Greenlander Inuit

“…This doubling of sample size was then corrected for by using robust variance estimates to allow for the duplication of the other within-person covariates in the same manner as previously described for use with twin data. 38 Multiple comparisons were not adjusted for because the analyses were based on an a priori hypothesis but were dealt with by describing all statistical analyses carried out. 39,40 All calculations were performed with the SPSS version 11.0 (SPSS Inc, Chicago, Ill) statistical package, except for the robust estimates, which were estimated with Stata software (StataCorp, College Station, Tex).…”

Genetic Factors in Nickel Allergy Evaluated in a Population-Based Female Twin Sample

“…A large twin odds ratio may on the other hand be interpreted as an effect of genes or common environmental factors, whereas larger twin odds ratio among MZ twins than among DZ twins is interpreted as an effect of genes. Betensky et al (2001) describe how the twin odds ratio may be estimated in a simple manner by use of logistic regression of each twins nickel allergy status, conditioned on the co-twin's nickel allergy status. This method is based on a random sample of twins, and each pair is included twice in the analysis.…”

Analysis of twin data ascertained through probands: The double‐entry approach

“…This measure of association is similar to the one proposed by Olson et al [1996]. In this parameterization, the model is identical to the one described by Betensky et al [2001]. The parameter p also describes, together with y 1i and y 2i , the marginal probability of being affected:…”

Associations of a novel IL4RA polymorphism, Ala57Thr, in Greenlander Inuit

“…This doubling of sample size was then corrected for by using robust variance estimates to allow for the duplication of the other within-person covariates in the same manner as previously described for use with twin data. 38 Multiple comparisons were not adjusted for because the analyses were based on an a priori hypothesis but were dealt with by describing all statistical analyses carried out. 39,40 All calculations were performed with the SPSS version 11.0 (SPSS Inc, Chicago, Ill) statistical package, except for the robust estimates, which were estimated with Stata software (StataCorp, College Station, Tex).…”