• Decision support, computerized
• Healthcare quality improvement
• Mortality (standardized mortality ratios)
• Quality improvement methodologies
• Statistics

Although it is clear that in the UK, standardised mortality rates have decreased dramatically over the past three decades,1 it may not be immediately apparent that this secular trend may substantially confound relatively short-term studies. Based on retrospectively obtained, uncontrolled data, Schmidt et al2 assert that introduction of an electronic physiological surveillance system reduced excess deaths. If, however, we control for the secular decrease in mortality rate, then this apparent benefit almost vanishes, as is shown in table 1, where I have applied the relevant decrease in standardised mortality rate for …