Sibling familial risk ratio of meningococcal disease in UK Caucasians
To quantify the host genetic component of meningococcal disease (MD) susceptibility, the sibling risk ratio (λs) was calculated as the ratio of observed MD cases among 845 siblings of 443 UK Caucasian cases to that expected, calculated from age-calendar year specific rates for England and Wales. Twenty-seven siblings contracted MD compared with an expected 0·89, generating a λs value of 30·3. Overestimation of λs due to Neisseria meningitidis exposure was minimized by excluding siblings with MD onset within set time points of the index case. Irrespective of whether siblings contracted MD more than 1, 3, 6, 9 or 12 months after the index case, the λs varied slightly (λs range: 8·2–11·9), suggesting that host genetic factors may contribute approximately one third of the total λs. Social class distribution did not differ between MD cases and the general population of England and Wales. This study is the first to calculate λs for MD and establishes that susceptibility to MD has a significant host genetic component.(Accepted January 30 2003)
c1 Author for correspondence.