Table 1

Relative contribution of the German DRS and biochemical and genetic markers to prediction of type 2 diabetes risk

ROC*
IDI
C statistic (95% CI)PAbsolute IDI (95% CI)Relative IDI (%)
DRS only0.8465 (0.8299–0.8630)Ref.Ref.Ref.
DRS and A1C0.8859 (0.8716–0.9003)<0.00010.0974 (0.0792–0.1155)34.11
DRS and glucose0.8672 (0.8515–0.8830)<0.00010.0553 (0.0407–0.0699)19.37
DRS and A1C0.8859 (0.8716–0.9003)Ref.Ref.Ref.
DRS, A1C, and glucose0.8926 (0.8785–0.9067)0.00400.0230 (0.0135–0.0325)6.01
DRS and glucose0.8672 (0.8515–0.8830)Ref.Ref.Ref.
DRS, glucose, and A1C0.8926 (0.8785–0.9067)<0.00010.0651 (0.0506–0.0797)19.11
DRS, glucose, and A1C0.8926 (0.8785–0.9067)Ref.Ref.Ref.
DRS, glucose, A1C, triglycerides, HDL cholesterol, γ-glutamyltransferase, and alanine aminotransferase0.9000 (0.8862–0.9137)0.00220.0223 (0.0142–0.0304)5.50
DRS, glucose, A1C, and genetic markers§0.8928 (0.8787–0.9070)0.73610.0014 (−0.0010–0.0039)0.36
DRS, glucose, A1C, triglycerides, HDL cholesterol, γ-glutamyltransferase, and alanine aminotransferase0.9000 (0.8862–0.9137)Ref.Ref.Ref.
DRS, glucose, A1C, triglycerides, HDL cholesterol, γ-glutamyltransferase, alanine aminotransferase, and adiponectin0.9023 (0.8887–0.9158)0.04710.0064 (0.0022–0.0107)1.50
DRS, glucose, A1C, triglycerides, HDL cholesterol, γ-glutamyltransferase, alanine aminotransferase, and hs-CRP0.9016 (0.8880–0.9151)0.15230.0029 (−0.0007–0.0066)0.69
DRS, glucose, A1C, triglycerides, HDL cholesterol, γ-glutamyltransferase, alanine aminotransferase, and genetic markers0.9002 (0.8865–0.9140)0.68680.0015 (−0.0010–0.0039)0.34
  • *The ROC curve is a plot of sensitivity versus false-positive rate across all possible cut points for a continuous predictor or prediction model. The area under the ROC curve (C statistic) is a measure of discrimination between case patients and control participants based on ranks and reflects the probability that the predicted risk is higher for a case subject than for a control subject. It ranges from 0.5 (no predictive ability) to a theoretical maximum of 1 (perfect discrimination)—the latter achieved if the scores or predicted risks for all case subjects are higher than those for all control subjects.

  • †IDI is the difference between two models in discrimination slopes, which reflect the mean difference in predicted risk between case and control subjects. Instead of the difference, relative IDI expresses the discrimination slope of the more extensive model (e.g., including a new marker) as proportional increase compared with the discrimination slope of the basic model.

  • ‡The German DRS combines baseline information on several risk factors to estimate the risk of developing type 2 diabetes (ref. 2). It is computed as follows: German DRS = 7.4 × waist (cm) − 2.4 × height (cm) + 4.3 × age (years) + 46 × hypertension (self-report) + 49 × red meat (each 150 g/day) − 9 × whole-grain bread (each 50 g/day) − 4 × coffee (each 150 g/day) × 20 × moderate alcohol (between 10 and 40 g/day) × 2 × physical activity (h/week) + 24 × former smoker + 64 × current heavy smoker (≥20 cigarettes/day).

  • §Unweighted count genetic score of 20 SNPs assuming an additive genetic model for each SNP and applying a linear weighting of 0, 1, and 2 to genotypes containing 0, 1, or 2 risk alleles. Participants were excluded if they had five or more genotypes missing. Scores for individuals with missing genotypes were standardized to those of individuals with complete data.