Table 1 Summary of family history studies

Reference	Population	CD probands, n	CD siblings, n	Total siblings, n	CD risk, %	Sibling relative risk*
Kuster et al (1989)4	Germany	265	13	453	2.87	28.7
Probert et al (1993)6	UK	424	19	984	1.93	19.3
Peeters et al (1996)7	Belgium	640	57	1728	3.3	33.0
Satsangi et al (1994)8	UK	433	20	782	2.56	25.6
Total		2003
Average risk					2.67	26.7
Average, weighted by study size					2.72	27.2

*Using a population prevalence of 0.001 for all studies.
Estimates of sibling relative risk for each study, mean value across studies, and a mean value weighting by study size (number of probands) are given.