The probability of ulcer in the absence of Hp infection is reportedly between 5 and 20 per cent (Choung & Talley, 2008) or even more (Ciociola, McSorley, Turner, Sykes, & Palmer, 1999); some suggest that in countries with low Hp infection base rates and early access to physicians, 35–45 per cent of patients with duodenal ulcers are Hp negative (e.g. Tang et al., 2009). Here, HP is linked to ulcer disease.