The effectiveness of case-finding for mental health problems in primary care.

backgroundThere is debate about the efficacy of screening and case detection for common mental health problems in general practice. There is enthusiasm for screening, but also conflicting evidence for its effectiveness and little research concerning implementation.

aimTo explore the efficacy of screening and case-finding for high prevalence psychological disorders in routine general practice. DESIGN OF STUDY: A cross-sectional survey (part of the MaGPie study).

settingLower North Island of New Zealand.

methodConsecutive patients from a random sample of GPs were screened using the General Health Questionnaire (GHQ-12). A stratified random sample of patients was selected, based on GHQ strata, and invited to participate in an indepth interview to assess their psychological health. Seventy GPs (90% response) and 775 patients (68.5% response) were included in analyses. Patients' GHQ-12 scores were compared with GP assessment of patients' psychological health using a 5-point scale of severity, and with the Composite International Diagnostic Interview (CIDI 1-month assessment).

resultsOverall 17.5% (95% CI = 13.8 to 21.1) of patients reached the threshold for CIDI diagnosis. GPs identified at least some psychological symptoms in the past 12 months in 70.3% (95% CI = 58.2 to 82.3) of patients reaching the CIDI threshold for diagnosis. Case-finding with a 'perfect' screening instrument had the potential to identify only five new cases per 100. The sensitivity and specificity of the GHQ-12 suggest it is not an appropriate tool for case finding in a general practice setting.

conclusionThe potential value of any screening and case-finding instrument in routine general practice must be considered in the context of current high rates of identification. Where continuity of care is a feature of usual management, case-finding is most efficient when focused on patients the GP has not seen in the past year.