Matched analysis of the 89 affected sibling pairs discordant for smoking at diagnosis
| Smokers | ||
|---|---|---|
| CD sibling | UC sibling | |
| 23 pairs were discordant for their diagnoses. In 21 of these pairs, the smoker had been diagnosed as having Crohn's disease (CD), and the non-smoker ulcerative colitis (UC) (McNemaras test with Yates' continuity correction p<0.0001, odds ratio 10.5, 95% confidence limits 2.6–92; Fisher-Irwin two tailed probability test p<10−8). There were only two affected sib pairs in which the smoker had developed UC and the non-smoker CD. | ||
| Non-smokers | ||
| CD sibling | 42 | 2 |
| UC sibling | 21 | 24 |