Update of the German Diabetes Risk Score and external validation in the German MONICA/KORA study

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Abstract

Aims

Several published diabetes prediction models include information about family history of diabetes. The aim of this study was to extend the previously developed German Diabetes Risk Score (GDRS) with family history of diabetes and to validate the updated GDRS in the Multinational MONItoring of trends and determinants in CArdiovascular Diseases (MONICA)/German Cooperative Health Research in the Region of Augsburg (KORA) study.

Methods

We used data from the European Prospective Investigation into Cancer and Nutrition (EPIC)-Potsdam study for extending the GDRS, including 21,846 participants. Within 5 years of follow-up 492 participants developed diabetes. The definition of family history included information about the father, the mother and/or sibling/s. Model extension was evaluated by discrimination and reclassification. We updated the calculation of the score and absolute risks. External validation was performed in the MONICA/KORA study comprising 11,940 participants with 315 incident cases after 5 years of follow-up.

Results

The basic ROC-AUC of 0.856 (95%-CI: 0.842–0.870) was improved by 0.007 (0.003–0.011) when parent and sibling history was included in the GDRS. The net reclassification improvement was 0.110 (0.072–0.149), respectively. For the updated score we demonstrated good calibration across all tenths of risk. In MONICA/KORA, the ROC-AUC was 0.837 (0.819–0.855); regarding calibration we saw slight overestimation of absolute risks.

Conclusions

Inclusion of the number of diabetes-affected parents and sibling history improved the prediction of type 2 diabetes. Therefore, we updated the GDRS algorithm accordingly. Validation in another German cohort study showed good discrimination and acceptable calibration for the vast majority of individuals.

Introduction

Within the past years, several diabetes prediction models have been developed [1], [2]. In addition to the development of new prediction models, there are ongoing efforts to further improve the accuracy of already published models. We have previously developed a risk prediction model, the German Diabetes Risk Score (GDRS), based on data of the European Prospective Investigation into Cancer and Nutrition (EPIC)-Potsdam study [3]. The main advantage of the GDRS was the inclusion of only non-invasive risk factors such as anthropometric measurements, lifestyle factors and nutrition and its accurate prediction of the five year risk for developing type 2 diabetes. Family history of diabetes is also a non-invasive risk factor and might improve risk prediction with the GDRS. Although it is a well-known risk factor for diabetes [4] and has been included in several other prediction models [1], it could not originally be included in the GDRS due to assessment in follow-up round 5. As this information is available now, the aim of our study was to determine whether information on family history improves discrimination and risk classification of the GDRS; to update the score calculation, if necessary; and to validate the prediction model in an independent cohort study, the MONICA (Multinational MONItoring of trends and determinants in CArdiovascular diseases)/KORA (Cooperative Health Research in the Region of Augsburg) study.

Section snippets

European Prospective Investigation into Cancer and Nutrition Potsdam study

The European Prospective Investigation into Cancer and Nutrition (EPIC)-Potsdam study is a prospective cohort study comprising 27,548 participants from the general adult population mostly aged 35 to 65 years in Potsdam and surrounding municipalities. Participants were recruited between 1994 and 1998 and followed-up each two to three years [5]. Follow-up achieved response rates of 96%, 95%, 91% and 90% for follow-up rounds 1, 2, 3 and 4 (by 31 August 2005) [6]. The baseline assessment included

Results

Baseline characteristics of the EPIC-Potsdam and MONICA/KORA studies are shown in Table 1. The 5-year-incidence of diabetes was 2.3% in the EPIC-Potsdam and 2.7% in the MONICA/KORA study population. Regarding the risk factors the two study populations were quite comparable. Participants in EPIC-Potsdam were on average younger, more likely to be female or less often current heavy smoker compared to MONICA/KORA study participants. Physical activity was more pronounced in EPIC-Potsdam which was

Discussion

We observed that extending the GDRS with information about the number of parents affected by diabetes and with sibling history of diabetes improved this prediction score in terms of discrimination and reclassification. The external validation in a German cohort showed overall good discrimination and acceptable calibration for the updated GDRS.

Considering the effort for assessment of this information, the inclusion of family history of diabetes resulted in a reasonable improvement of the GDRS in

Conflict of interest

No conflicts of interest.

Acknowledgments

We thank Ellen Kohlsdorf for data management and all study participants of EPIC-Potsdam and MONICA/KORA.

This work was supported in part by a grant from the German Federal Ministry of Education and Research (BMBF) to the German Center for Diabetes Research (DZD e.V.).

The recruitment phase of the EPIC-Potsdam Study was supported by the Federal Ministry of Science, Germany (01 EA 9401) and the European Union (SOC 95201408 05F02). The follow-up of the EPIC-Potsdam Study was supported by German

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