a1 Medical Research Council Epidemiology and Medical Care Unit, The Wolfson Institute of Preventive Medicine, The Medical College of St Bartholomew's Hospital, Charterhouse Square, London EC1M 6BQ
a2 The London School of Hygiene and Tropical, Medicine, Keppel Street, London WC1E 7HT
a3 Communicable Disease Surveillance Centre, 61 Colindale Avenue, London NW9 5EQ
a4 Department of Health, Skipton House, 80 London Road, London SE1 6LW
a5 Coventry Public Health, Coventry and Warwickshire Hospital, Stoney Stanton Road, Coventry CV1 4FH
a6 Central Public Health Laboratory, 61 Colindale Avenue, London NW9 5HT
Pilot studies to test methods to determine the incidence, agents, risk factors and socioeconomic costs of infectious intestinal disease (IID) in England were carried out as recommended by the Committee on the Microbiological Safety of Food (the Richmond Committee) by eight general practices. There were case control and enumeration studies of patients presenting to general practice with IID, a population-based prospective cohort study, and a survey of socioeconomic costs of cases of IID. Information on risk factors was obtained by questionnaire (self-administered compared with interview) and a stool sample was requested on all cases and controls. Response rates in the GP case control study were 75% for case questionnaires and 74% for stools; for controls the figures were 70% and 68% respectively. The acceptance rate into the cohort study was 49%; this was significantly higher where phone contact was made. The rate was similar if recruitment was by individual or household. Follow-up of the cohort by negative reporting was complete for up to 6 months. Direct postage by subject was required to obtain fresh stool specimens. Estimates were obtained of presentation rates of IID and the distribution of risk factors which were used to plan the main study. The pilot study demonstrated that it is possible to undertake a national study based in general practice to determine the incidence of IID in the population and presenting to GPs and its agents, risk factors and costs.
(Accepted November 15 1994)