The recent study by Noble et al (Gut 2005;54:1416–20) did not find an association of the DLG5 G113A polymorphism with either inflammatory bowel disease (IBD) or Crohn’s disease (CD). Previous studies in other European populations had reported an increase in 113A allele frequency in IBD and CD patients^1,2 but, in striking contrast, Noble et al reported a trend towards decreased carrier frequency for the 113A allele in IBD (p = 0.069) and CD (p = 0.057) patients. We believe there is reason to re-examine the genotype data used in the report of Noble et al.

Firstly, there was a significant difference in the proportion of missing genotypes between the IBD patients and controls (p<0.00001, Fisher’s exact test). Using the data in tables 1 and 3, the missing genotype rate was 13% in controls and 4% in IBD patients. This difference strongly suggests differences in DNA quality or genotyping process between the IBD and control samples.

Secondly, using …