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C H A P T E R 2
Diagnosis and
Classification of
Diabetes in Children
DEFINITION
The diagnosis of diabetes includes a wide array of diseases that are characterized by persistent hyperglycemia (Table 1).
Insulin is the only physiologically significant hypoglycemic hormone. Therefore, hyperglycemia must be the result of impaired secretion of insulin from the β-cells of the pancreas; resistance to the effect of insulin in the liver, muscle, and fat cells; or a combination of these pathophysiologic situations.
The current criteria for diabetes include categories of impaired glucose tolerance (IGT) and impaired fasting glucose that are considered to be states of pre-diabetes, reflecting an appreciation of the fact that these preclinical states are associated with increased cardiovascular morbidity (1).
CLASSIFICATION
Tables 2–6 outline the features of the types of diabetes that need to be considered in children and adolescents, based on what is known of the etiology, in keeping with the American Diabetes Association’s Expert Committee on the Diagnosis and Classification of Diabetes Mellitus (1). Contemporary understanding of the pathogenesis of various forms of diabetes made previous classification based on treatment inappropriate.
TABLE 1. Criteria for the Diagnosis of Diabetes
Symptoms plus random plasma glucose concentration ≥200 mg/dl (11 mmol/l), or
Fasting plasma glucose ≥126 mg/dl (7 mmol/l), or
2-h plasma glucose ≥200 mg/dl (11 mmol/l) during an oral glucose tolerance test. The test should be performed using a glucose load containing the equivalent of 75 g anhydrous glucose dissolved in water for individuals weighing >43 kg and 1.75 g/kg for individuals weighing ≤43 kg.
In the absence of marked hyperglycemia with decompensation, these criteria should be confirmed by repeat testing on a different day. The oral glucose tolerance test is not recommended for routine clinical use. Impaired glucose tolerance (IGT) is defined by a 2-h plasma glucose level between 140 and 200 mg/dl. Impaired fasting glucose is defined by a level between ≥110 and <126 mg/dl. From the Expert Committee on the Diagnosis and Classification of Diabetes Mellitus (1).
Table 2. Immune Mediated Type 1 Diabetes
β-Cell destruction, usually leading to absolute insulin deficiency
Occurs throughout childhood, with as great or greater incidence under 10 years of age as in 10–20 year olds
Much less frequent in Asians and native North Americans and somewhat less frequent in African-Americans than in those of European origin
Associated with HLA specificities
First-degree relatives of 5–10% of patients affected
Polygenic inheritance
Equal sex ratio
Autoantibodies to insulin (IAA), islet cell cytoplasm (ICA), glutamic acid dehydrogenase (GAD), or tyrosine phosphatase (insulinoma-associated) antibody (IA-2 and IA-2β) at diagnosis in 85–98%
Ketosis or ketoacidosis common at onset
Period of weight loss, polyuria, polydipsia, fatigue common; nonspecific symptoms often missed in infants and toddlers
Signs of insulin resistance, such as hypertension or acanthosis nigricans absent at diagnosis
Low to absent insulin secretion, as indicated by C-peptide concentration; however, following initial diagnosis and treatment, partial recovery can last for months to (very rarely) several years
Table 3. Idiopathic Type 1 Diabetes
May be difficult to distinguish from immune mediated type 1 diabetes
Includes what is referred to as atypical diabetes mellitus (ADM) or “Flatbush” diabetes, that has been variously considered as a form of type 1 diabetes, type 2 diabetes, or maturity onset diabetes of the young (MODY) (1–5)
Occurs throughout childhood, and rarely past age 40
Only described in African-American individuals
Not associated with HLA specificities
Strong family history in multiple generations with autosomal dominant pattern of inheritance
Not associated with obesity beyond that in the general African-American
