The state of variability: A vision for descriptors of glycaemia

Abstract Glycaemic control (GC) in the intensive care unit is contentious. Hyperglycaemia, hypoglycaemia, and glycaemic variability are all associated with increased morbidity and mortality. While some studies and physiological evidence suggests GC should benefit hyperglycaemic patients, others show no or negative effects and increased incidence of hypoglycaemia. Interpretation of results is made more difficult by differences in the measurement and reporting of glycaemic control, blood glucose levels and variability in patients. In addition, target ranges for glycaemic control are not universally accepted, and higher targets are often used out of fear of hypoglycaemia, rather than their relationship to a clinical outcome. Importantly, current metrics are mostly mathematically derived, and then related to a potential clinical outcome, yielding highly variable results, while very few are clinically defined first. Thus, the goal metrics for control are not directly clinically defined. This paper reviews differences in the reporting of BG level and its variability in literature. It then proposes a vision for improved description of glycaemia and presents a continuous glucose monitoring (CGM) sensor-based method to better quantify glycaemic level and variability, based on clinically defined metrics. A case study of this new method is presented using CGM sensor data from a study of 614 infants at risk of neonatal hypoglycaemia. Results show the new clinically defined method is able to describe changes in glycaemic level and variability in these patients and presents a flexible way forward for accurately describing state and variability from a clinically defined perspective. This method may provide better insight to patient glycaemia over time, and thus provide scope for improved control of glycaemia.