Calculating Odds Ratios For Major Alleles

Question

[Andrews]

Is it possible to calculate the odds ratio for the major allele when the odds ratio for the minor allele is reported? For example for the gene CLU (http://www.alzgene.org/meta.asp?geneID=323) the reported odds ratio for the minor allele is 0.89 but what would the odds ratio for major allele be?

[felixsmith.abc]

Finding the odds ratio for the major allele when you have the odds ratio for the minor allele is straighforward.

Take the reciprocal

OR_of_majallele=1/OR_of_minallele

My additional question is how to get the standard error of the major allele - a straightforward reciprocal doesn't work. But the reciprocal of the upper and lower bound of a confidence interval (mean+1SE for simplicity) might...?

Does this work..?

SE_of_majallele=(((1/(OR_of_minallele-SE_of_minallele))-(1/(OR_of_minallele-SE_of_minallele)))/2

Answer 1

[Andrews]

Discovered this is called the reciprocal odds ratio.

http://en.wikipedia.org/wiki/Odds_ratio#Invertibility_and_invariance