Stratum-specific likelihood ratios of two versions of the General Health Questionnaire

Background. In other branches of epidemiology, stratum specific likelihood ratios (SSLRs) have been found to be preferable to fixed best threshold app roaches to screening instruments. This paper presents SSLRs of GHQ-12 and G HQ-28 and compares the SSLR method with the traditional optimal threshold a pproach. Methods. Random effects meta-analysis and meta-regression were used to obta in pooled estimates of SSLRs of the two questionnaires for the 15 centres p articipating in the WHO study of Psychological Problems in General Health C are. We illustrated the use of SSLRs by applying them to random samples of patients from centres with different backgrounds. Results. For developed and urban centres, the estimates of SSLRs were homog eneous for 10 out of 12 strata of the GHQ-12 and GHQ-28. For other centres, the overall results, which were heterogeneous for six out of 12 strata. we re deemed the currently available best estimates. When we applied these res ults to centres with different prevalences of mental disorders and backgrou nds, the estimates matched the actually observed closely. These examples sh owed how the SSLR approach is more informative than the traditional thresho ld approach. Conclusions. Those working in developed urban settings can use the correspo nding SSLRs with reasonable confidence. Those working in Iron-urban or deve loping areas may wish to use the overall results, while acknowledging that they must remain less certain until further research can explicate heteroge neity. These SSLRs have been incorporated into nomograms and spreadsheet pr ogrammes so that future researchers can swiftly derive the post-test probab ility for a patient or a group of patients from a pre-test probability and GHQ score.