Development and validation of the DIabetes Severity SCOre (DISSCO) in 139,626 individuals with type 2 diabetes: a retrospective cohort study

Objective: Clinically-applicable diabetes severity measures are lacking, with no previous studies compared their predictive value to HbA1c. We developed and validated a type 2 diabetes severity score (DISSCO) and evaluated its association with risks of hospitalisation and mortality, assessing its additional risk information to socio-demographic factors and HbA1c. Research Design and Methods: We used UK primary and secondary care data for 139,626 individuals with type 2 diabetes between 2007-2017, aged ≥35years, registered in 400 general practices. The study cohort was randomly divided to a training (N=111,748, 80%) to develop the severity tool, and validation cohort (N=27,878). We developed baseline and longitudinal severity scores using 34 diabetes-related domains. Cox regression models (adjusted for age, gender, ethnicity, deprivation, and HbA1c) were used for primary (all-cause mortality) and secondary outcomes (hospitalisation due to: any cause, diabetes, hypoglycaemia, or cardiovascular disease/procedures). Likelihood-ratio (LR) tests fitted to assess significance of adding DISSCO to the socio-demographics and HbA1c models. Results: A total of 139,626 patients aged 63±12 years, 45% women, 83% White, 18% from deprived areas were included. Mean baseline severity scores was 1.3±2.0. In the training cohort, 27,362 (20%) people died, and 99,951 (72%) had ≥1 hospitalisation. A 1-unit increase in baseline DISSCO was associated with higher hazard of mortality (HR: 1.14, 95%CI: 1.13; 1.15, AUROC=0.76), and cardiovascular hospitalisation (HR: 1.45, 95%CI: 1.43; 1.46, AUROC=0.73). The LR tests showed that adding DISSCO to socio-demographic variables significantly improved the predictive value of survival models, outperforming the added value of HbA1c for all outcomes. Findings were consistent in the validation cohort. Conclusions: Higher levels of DISSCO are associated with higher risks for hospital admissions and mortality. The new severity score had higher predictive value than the proxy used in clinical practice, HbA1c. This reproducible algorithm can help practitioners stratify clinical care of patients with type 2 diabetes.