Measurement of the costs of hospital infection by prevalence surveys.

Data from seven single-day prevalence surveys were used to assess the costs of hospital-acquired infection (HAI) by matching infected cases with controls and reviewing patient case notes for details of mortality, length of hospitalization and antibiotic treatment costs. Many cases with a high risk of HAI could not be matched and probably had inevitable infection. Cases that could be matched had the same risks of HAI as the controls, and these infections were potentially avoidable. Compared with controls, infected patients had an excess mortality rate of 7.4%, an average excess hospital stay of 23 days and an average excess antibiotic expenditure of US$190. By extrapolation we calculate that the annual costs of avoidable HAI at Prince of Wales Hospital is now approximately 130 lives, 42 000 bed-days and US$0.3m of antibiotics; costs of a similar magnitude have already been saved by a programme of hospital infection control. We conclude that hospital-acquired infection is very expensive, infection control is highly cost-effective, and prevalence surveys are practical tools for the measurement of rates and costs of hospital infection.