The survey form of SCAN: the feasibility of using experienced lay survey interviewers to administer a semi-structured systematic clinical assessment of psychotic and non-psychotic disorders

Background. The success of large scale surveys depends on well designed questionnaires and the skills of lay interviewers. Discrepancies in prevalence rates between epidemiological surveys and poor agreement between survey interviewer and clinician diagnostic interviews are giving rise to increasing concern among researchers, public health planners and policy developers. New approaches to information collection are called for. The feasibility of training experienced survey interviewers in semi-structured, clinical, diagnostic interviewing has never been investigated systematically across the range of neurotic and psychotic disorders. Methods. Eight experienced survey interviewers from the Office for National Statistics (ONS) were selected and underwent extended training in a Survey Form of SCAN (SCAN-SF). Sixty-four adults, including a majority of psychiatric in-patients were assessed by ONS interviewers and reinterviewed within a week by SCAN-trained clinicians. Feedback was sought from interviewers and trainers. Results. Trainers found lay interviewers coped at least as well with psychotic as with neurotic symptoms. Concordance for any disorder was 0.74 (95% CI: 0.57 to 0.91); for any specific psychotic disorder 0.63 (0.40 to 0.86); for any specific neurotic disorder 0.63 (0.43 to 0.83). Sensitivity ranged from 0.6 to 0.9 and specificity from 0.8 to 0.9. There was no evidence of rater bias. Conclusions. These preliminary findings are very promising. However, before the SCAN-SF, administered by carefully trained lay interviewers, can be recommended in large scale surveys, further evaluations of its feasibility and reliability in the general population are needed.