Insulin Secretion Capacity as a Crucial Feature to Distinguish Type 1 From Type 2 Diabetes and to Indicate the Need for Insulin Therapy - A Critical Discussion of the ADA/EASD Consensus Statement on the Management of Type 1 Diabetes in Adults

Abstract

In the recently published consensus statement on the treatment and management of type 1 diabetes issued by experts from the American (ADA) and European (EASD) diabetes societies, measurement of endogenous insulin secretion using fasting C-peptide is recommended as a diagnostic criterion. In contrast, our group recently suggested fasting C-peptide/glucose ratio (CGR) for the determination of endogenous insulin secretion. In addition, this ratio may turn out as a potential decision aid for pathophysiologically based differential therapy of diabetes. In this comment, the following points will be discussed: i) CGR as the basis of differential diagnosis of type 1 diabetes, ii) CGR as the basis of treatment decisions for or against insulin in diabetes, and iii) the ease of application of CGR in clinical practice. The use of CGR may complement the ADA/EASD recommendations and should provide a practical application in clinical practice.

Fig. 1

ADA/EASD Consortium flow chart for screening for suspected type 1 diabetes in newly diagnosed adults, based on data from white European populations. Figure with permission from Holt et al. (Holt RIG, DeVries JH, Hess-Fischl A et al. The management of type 1 diabetes in adults. A consensus report by the American Diabetes Association [ADA] and the European Association for the Study of Diabetes [EASD]. Diabetologia 2021; 64: 2609–2652) [rerif]

Fig. 2

A simplified alternative proposal for testing suspected type 1 diabetes in newly diagnosed adults

Fig 3

Nomogram for simple determination of fasting C-peptide-glucose ratio (CGR; C-peptide in pmol/L, glucose in mg/dL) as a measure for estimation of endogenous insulin secretory capacity. Different units of measurement are reported by different laboratory providers (C-peptide in pmol/L or µg/L), glucose in mmol/L or mg/dL). The normogram can be used for easy and simple determination of the CGR for different units. C-peptide was measured with Siemens ADVIA Centaur XPT.; Pink field: CGR<2, insulin secretion deficit. Insulin therapy needed; the lower CGR, the more likely basal-bolus insulin therapy.; Blue field: CGR2–5, impaired endogenous insulin secretion. Basal insulin therapy in combination with other antidiabetic agents.; Green field: CGR>5, preserved endogenous insulin secretion. Usually, no insulin therapy needed, but oral antidiabetic agents and incretin analogs.; Figure courtesy of Mr. Sven Bachofner (Sanofi).