- William Eaton, professor (, )
- Preben Bo Mortensen, professor,
- Esben Agerbo, assistant professor,
- Majella Byrne, assistant professor,
- Ole Mors, professor
- Department of Mental Health, Bloomberg School of Public Health, Johns Hopkins University, 624 North Broadway, Baltimore, MD 21205, USA
- Institute of Basic Psychiatric Research, Psychiatric Hospital in Aarhus, Skovagervej 2, 8240 Risskov, Denmark
EDITOR—As noted in the original paper, we agree that coeliac disease is almost certainly underascertained in the study: but we do not agree it is a confounding factor. The question is whether the ascertainment in cases and controls, and in cases and controls with other autoimmune intestinal diseases, is differential (biased).
The numbers are small, but the logic of bias is weak in cases, and even weaker in parents. The figure of 0.5 in the table, for prevalence in controls, includes coeliac disease in controls or their parents (as noted in the table). The numbers with coeliac disease in the controls were: 27 controls, 48 mothers of controls and 18 fathers of controls (93/199 915, or 0.5 per 1000). This compares to figures given in the paper of 4, 5, and 3 in cases, mothers of cases, and fathers of cases, respectively (12/7997, or 1.5 per 1000).
We are also not yet convinced. But, we are led to direct our attention further in this area in the light of current research, including the availability of new screening tests for coeliac disease, which identify subclinical cases; prior trials of gluten withdrawal which usually identify a small proportion who respond positively1–4; and some dramatic case studies.5
Competing interests None declared.