Using qdec to compare groups of twins?
Hello,
Could you please advise as to whether or not the following analysis is suitable?
I would like to compare groups of monozygotic twins (MZ concordant vs. MZ control ; MZ discordant affected twin vs. unaffected twin) using qdec. This is not as straightforward as group comparisons usually are because I cannot make the assumption of all data being independent as twin pairs are, obviously, related to one another.
To get around this issue I have started a qdec analysis and added a category 'pair' in which twin pairs share a category as follows (qdec.table.dat), in order to indicate that they have shared genetic and environmental influence:
subject no
subjid pair diagnosis age gender
1 a MZ_Discord_Well ... ...
2 a MZ_Discord_Ill
3 b MZ_Discord_Ill
4 b MZ_Discord_Well
5 c MZ_Discord_Well
6 c MZ_Discord_Ill
7 h MZ_Discord_Well
8 h MZ_Discord_Ill
9 l MZ_Discord_Well
10 l MZ_Discord_Ill
11 m MZ_Discord_Well
12 m MZ_Discord_Ill
13 n MZ_Discord_Well
14 n MZ_Discord_Ill
15 p MZ_Discord_Well
16 p MZ_Discord_Ill
17 s MZ_Discord_Well
18 s MZ_Discord_Ill
19 t MZ_Discord_Well
20 t MZ_Discord_Ill
I would appreciate if you could suggest a more robust way around this.
Many thanks,
Rysia
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