PhD thesis - University of Hertfordshire Research Archive

presentation and severity, foreign and UK travel, food consumption (~20
questions relating to the main food groups), milk and water consumption,
recreational water activity, contact with animals and contact with other ill
people. Exposures related to the fourteen days prior to the onset of patients‟
illness.
Collaborators formatted questionnaires as to their local style to encourage
participation: the rationale being that individuals would prefer to receive a
questionnaire from local teams rather than a national body. They were also
permitted to add questions, if inclined, to answer specific research questions
of their own, but could not to remove any, therefore maintaining the minimum
dataset. Questionnaires were administered according to existing public or
environmental practice, in that cases were contacted by post, by telephone or
by personal visit depending on what method was currently in place. The
study was piloted in two health authorities for one month prior to the start of
the study and the effectiveness of the questionnaire as a surveillance tool
was assessed at this time.
Concurrently, campylobacter isolates from clinical microbiology laboratories
within the health authority catchment areas were referred to the CRU for
confirmation and characterisation (speciation (Bolton et al., 1992), serotyping
(Frost et al., 1998), phage typing (Frost, Kramer, & Gillanders, 1999) and
antimicrobial resistance testing (Thwaites & Frost, 1999).
Electronic epidemiological and microbiological data were merged in Microsoft
Access. The two datasets were linked initially using patient‟s surname and
dates of birth. The forename, region and onset/specimen dates for linked
cases were then compared in both datasets to ensure that the linkage was
correct. For unlinked records a number of strategies were employed to
identify the respective record in the other dataset. Searches of first name,
date of birth and postcode were undertaken and the person details of
potential matches compared. The first few letters of surnames and first
names were analysed in the same way. Finally, for each case, the other
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