eTable 3. Laboratory parameters for the diagnosis of type 2 diabetes (2).

Laboratory parameter	Advantages	Disadvantages
FPG	– Simple to perform – Independent of age, hemoglobinopathy, hematological disorders, and red blood cell turnover	– Individual variation from day to day – Time-of-day fluctuations (therefore, test performed, e.g., between 7:00 am and 9:00 am) – Uncertainty regarding fasting status – Preanalytical pitalls (standardized processing and suitable blood collection tubes necessary)
HbA1c	– Independent of time of day and fasting status – Independent of muscle work and site of blood collection – Low individual variation from day to day – Reflects mean plasma glucose for the previous 8–12 weeks	– Multiple interferences – Analytical problems (insufficiently reproducible) – Among other factors, dependent on age and ethnic origin
oGTT	– Reference test (26) – Only test for the diagnosis of impaired glucose tolerance – Independent of age, hemoglobinopathy, hematological disorders, and red blood cell turnover	– Lower reproducibility than FPG and HbA1c – More complex and prone to errors – Intraindividual fluctuations – Preanalytical pitifalls (standardized processing and suitable blood collection tubes necessary)
CPG	– Fasting status not required – Simple to perform – Independent of age, hemoglobinopathy, hematological disorders, and red blood cell turnover	– Intraindividual fluctuations – Fluctuations depending on length of fasting status and the type and volume of previous food intake – Preanalytical pitfalls (standardized processing and suitable blood collection tubes necessary) – Not suitable for the exclusion of a diagnosis due to lack of standardization

The table is based on the clinical experience of the guideline group.

CPG, casual plasma glucose; HbA1c, hemoglobin A1c; FPG, fasting plasma glucose; oGTT, oral glucose tolerance test