Table 4.

Diagnostic criteria for acute‐onset, slowly progressive, and fulminant type 1 diabetes (findings of relevance shown in square brackets)

Criteria	Acute‐onset type 1 diabetes	Slowly‐progressive type 1 diabetes (SPIDDM)	Fulminant type 1 diabetes
1. Symptoms of hyperglycemia and ketosis †	Affected individuals are expected to present with thirst, polydipsia, and polyuria, leading to the onset of ketosis or ketoacidosis within 3 months.	While affected individuals are expected to present with ketosis or ketoacidosis at disease onset or diagnosis, they do not require immediate insulin therapy.	Affected individuals are expected to present with the symptoms of hyperglycemia, e.g., thirst, polydipsia, and polyuria, leading to the onset of ketosis or ketoacidosis within about 1 week of onset of these symptoms; they are also expected to present with ketosis at initial consultation.
2. Glycemic status/need for insulin therapy	Affected individuals are expected to require continuous insulin therapy from early after diagnosis of diabetes; they may also be expected to experience a transient ‘honeymoon phase’. ‡	While favorable glycemic control can often be achieved without insulin therapy in individuals early after disease onset, insulin therapy is considered effective in delaying their progression to an insulin‐dependent state.	Affected individuals are expected to have casual blood glucose values 288 mg/dL or higher and HbA1c values <8.7% [thus necessitating initiation of insulin therapy].
3. Islet autoantibodies §	Affected individuals are expected to be confirmed positive for either GAD antibodies, IA‐2 antibodies, IAA, ZnT8 or ICA antibodies during their clinical course (where IAA positivity needs to be confirmed prior to initiation of insulin therapy).	Affected individuals are expected to be confirmed positive for either GAD antibodies or ICA during their clinical course.	[As a rule, affected individuals are expected to test negative for islet autoantibodies.]
4. Endogenous insulin secretion	Affected individuals may not be confirmed positive for islet autoantibodies but are expected to have fasting serum C‐peptide values <0.6 ng/mL thus suggesting a deficit in endogenous insulin secretion.	[Some individuals may not show evidence of decreased endogenous insulin secretion, irrespective of their autoantibody values.]	Affected individuals are expected to have urinary C‐peptide values <10 μg/day at disease onset or fasting serum C‐peptide values <0.3 ng/mL and post‐glucagon load (or 2‐h postprandial) C‐peptide values <0.5 ng/mL.
Diagnosis	Individuals who have met the above criteria 1–3 are to be diagnosed with acute‐onset (autoimmune) type 1 diabetes. Those who have met the above criteria 1, 2, and 4 are to be diagnosed with acute‐onset type 1 diabetes. Those who have met the above criteria 1 and 2 but not 3 and 4 are to be re‐evaluated after an interval with the diagnosis put on hold. Those who have met the criteria for fulminant type 1 diabetes are to be diagnosed as such.	Individuals who have met the above criteria 1 and 3 are to be diagnosed with slowly‐progressive type 1 diabetes.	Individuals who have met the above criteria 1, 2 and 4 are to be diagnosed with fulminant type 1 diabetes.
Other relevant findings	Individuals with single‐gene disorders, such as HNF‐1α gene, mitochondrial gene, KCNJ11 gene mutations, are to be excluded from assessment.	Insulin therapy may be initiated in affected individuals from early after diagnosis while they are still not in an insulin‐dependent state.	Some may lead to the onset of ketosis or ketoacidosis within about 1–2 weeks. The onset of fulminant type 1 diabetes may be associated with pregnancy. Exocrine pancreatic enzymes, e.g., amylase, lipase, and esterase 1, are shown to be elevated in 98% of affected individuals. Upper airway and gastrointestinal symptoms are noted in 70% of affected individuals. Fulminant type 1 diabetes is shown to be linked to HLA DRB1*04:05–DQB1*04:01.

^†Ketosis, diagnosed when individuals are found positive for urinary ketone bodies or associated with increased serum ketone levels.

^‡Honeymoon phase, defined as a phase during which glycemic control may be achieved without insulin therapy for months after initial insulin therapy implemented early after diagnosis.

^§Islet auto antibodies include glutamic acid decarboxylate (GAD) antibodies, insulinoma‐associated protein‐2 (IA‐2) antibodies, insulin autoantibodies (IAA), zinc transporter 8 (ZnT8) antibodies, and islet cell antibodies (ICA).