Performance of screening questionnaires and risk scores for undiagnosed diabetes: the KORA Survey 2000.

BACKGROUND: Validation of published screening questionnaires and risk scores for undiagnosed diabetes has typically not been performed in independent population samples.
METHODS: Oral glucose tolerance tests were performed in 1353 participants (aged 55-74 years) without known diabetes in the Cooperative Health Research in the Region of Augsburg (KORA) Survey 2000, Augsburg, Germany. Sensitivity, specificity, and the area under the receiver operating characteristic curve (AUC) for undiagnosed diabetes were calculated for various screening questionnaires.
RESULTS: Four screening tests (Rotterdam Diabetes Study, Cambridge Risk Score, San Antonio Heart Study, and Finnish Diabetes Risk Score) were applied to the KORA data. The AUCs were 61% (95% confidence interval [CI], 56%-66%) for the Rotterdam Diabetes Study, 65% (95% CI, 60%-69%) for the Finnish Diabetes Risk Score (P=.10 vs Rotterdam), and 67% (95% CI, 62%-72%) for the Cambridge Risk Score (P<.001 vs Rotterdam). A predictive model including fasting glucose level (San Antonio Heart Study) yielded an AUC of 90% (P<.01 vs all 3 questionnaires); however, this was not significantly different from fasting glucose level alone (AUC, 89%; P=.46). The sensitivities, specificities, and predictive values of questionnaires were substantially lower than originally described, which was mainly due to population variation of risk factors compared with the KORA sample (age, body mass index, antihypertensive medication, and smoking).
CONCLUSIONS: Currently proposed questionnaires yielded low validity when applied to a new population, most likely due to differences in population characteristics. Performance of diabetes risk questionnaires or scores must be assessed in the target population where they will be applied.