The inclusion criteria were: patients of Thai nationality, over 15 years of age and
resident in one of the five districts indicated in figure one.
The exclusion criteria were: patients with a change of
permanent residence after initial diagnosis as this might
make follow-up patients difficult, and individuals with
symptoms of mental illness which might affect their
ability to provide accurate data. The participants were
selected by stratified sampling from the clinics and
hospitals, and the quota from each to be included was
calculated as a proportion of the total number of patients
treated in each hospital over the time period. These
quotas ranged from nine to 125 patients for the 16 study
sites. Recruitment at each clinic or hospital took place
until the required number of respondents agreed to
participate. All had been treated within one month of
participation in the survey.