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