Report of the Committee of Japan Diabetes Society on the Classification and Diagnostic Criteria of Diabetes Mellitus the Committee of Japan Diabetes Society for the Diagnostic Criteria of Diabetes Mellitus

Abstract

In 1995, the Japan Diabetes Society (JDS) appointed the Committee for the Classification and Diagnosis of Diabetes Mellitus. The following report of the Committee was prepared, taking account of the previous reports from JDS (1970 and 1982), opinions of the council members of the JDS, recent reports of the Expert Committee of American Diabetes Association (ADA) and the WHO Consultation, and new data presented at the JDS Symposium on the Classification and Diagnosis of Diabetes Mellitus held in June, 1998. Concept of diabetes mellitus : Diabetes mellitus is a group of diseases characterized by chronic hyperglycemia and other specific metabolic abnormalities, with heterogenous etiologies in which both genetic and environmental factors are involved. After a long duration of metabolic derangement, specific complications of diabetes (retinopathy, nephropathy and neuropathy) may occur. Arteriosclerosis is also accelerated in the presence of diabetes. Depending on the severity of metabolic abnormality, diabetes may be asymptomatic, may present with characteristic symptoms such as thirst, polyuria, polydipsia, weight loss, or it may progress to ketoacidosis and coma. Classification : To describe diabetes and abnormal glucose metabolism, we adopt both etiological classification and staging of pathophysiology due to the degree of deficiency of insulin effect. Etiological classification of diabetes and related disorders of glycemia includes, (1) type 1, (2) type 2, (3) those due to specific mechanism and diseases, and (4) gestational diabetes mellitus. Type 1 is characterized by destructive lesion of β cells due to either autoimmune mechanism or unknown cause. Type 2 is characterized by decreased insulin secretion plus decreased insulin sensitivity (insulin resistance). Category (3) includes two subgroups; in subgroup A, genetic susceptibility to diabetes has been identified by DNA analysis, and in subgroup B, diabetes is associated with other pathologic conditions or diseases. The staging of glucose metabolism includes normal, borderline and diabetic stages. The diabetic stage is further classified into 3 substages ; non-insulin requiring, insulin-requiring for glycemic control, and insulin-dependent for survival. The former two correspond to the previous NIDDM and the latter to IDDM. In each individual, these stages may vary according to the deterioration of the disease process or the improvement of metabolism, either spontaneously or by treatment. Diagnosis : The confirmation of chronic hyperglycemia is a prerequisite for the diagnosis of diabetes mellitus. The state of glycemia is classified into 3 categories; diabetic type, borderline type (or impaired glycemia) and normal type (or normoglycemia). Diabetic type is defined when fasting plasma glucose (FPG) is 126mg/dl or higher, and/or plasma glucose 2 hours after 75g glucose load (2 hPG) is 200mg/dl or higher. Casual plasma glucose higher than 200mg/dl is also regarded as indicating diabetic type. Normal type is defined when FPG is below 110mg/dl and 2 hPG below 140mg/dl. Borderline type (impaired glycemia) is defined in those who belong neither to diabetic nor to normal types. These glycemic cutoff values represent venous plasma glucose levels. The persistence of ‘diabetic type' in a subject indicates that he or she has diabetes. The procedure of clinical diagnosis : 1. Diabetes mellitus is diagnosed when hyperglycemia meeting criteria for ‘diabetic type' is recognized on more than 2 occasions examined on separate days. Before confirmation by the second plasma glucose testing, the subject is regarded simply to have ‘diabetic type'. 2. The diagnosis of diabetes can be made by a single plasma glucose test meeting criteria for ‘diabetic type', when one of the following three conditions exists; (1) the subject has typical symptoms of diabetes mellitus (i. e. thirst, polyuria, polydipsia, weight loss), (2)HbA1C is 6.5% or higher (HbA1C should be determined according to the recommendation of JDS Committee for Standardization of Glycohemoglobin), (3) unequivocal diabetic retinopathy is detected. 3. If the above conditions (i. e. 1. or 2.) existed in the past and were well documented, the subject is to be diagnosed either to have diabetes or suspected of diabetes regardless of the glycemic status at present. 4. If the diagnosis of diabetes cannot be established after the repeated tests of plasma glucose, clinical informations should be evaluated in order to assess the probability of developing diabetes. In such cases, re-testing of plasma glucose after some interval is recommended. 5. At clinical diagnosis, the physician should assess not only the presence or absence of diabetes, but also its etiology and glycemic stage, and the presence of diabetic complications. Epidemiological aspect: In order to determine the prevalence of diabetes in an epidemiological survey, ‘diabetic type' may be regarded as ‘diabetes'. The use of 2 hPG cutoff level of ≧ 200mg/dl is recommended. If it is difficult, the FPG cutoff level of ≧ 126mg/dl can be used together with the description of criteria used for that survey. Screening : The most important point is not to overlook ‘diabetes' at the initial testing. Not only parameters of hyperglycemia, but also clinical informations such as family history, obesity etc, should be included to screen subjects for further testing. Children and aged people : For children, 1.75g/kg glucose is used instead of 75 g (maximum = 75 g). The cutoff levels for categories of glucose metabolism is the same for children and aged people. Normal type and borderline type (normo-and impaired glycemia) : Only FPG and 2 hPG are adopted as cutoff values, but in clinical situations, it is recommended to measure plasma glucose also at 30 and 60 minutes during 75 g oral glucose tolerance test (OGTT). It is also recommended to measure insulin levels as well. They help predict the risk of developing diabetes in the future. Among people with ‘normal type', those with 1 hPG higher than 180mg/dl are at higher risk to develop diabetes than those with 1 hPG lower than 180mg/dl. The borderline type in this report corresponds to the sum of impaired fasting glucose or glycemia (IFG) plus impaired glucose tolerance (IGT) by ADA and WHO new recommendations. Subjects in this category are at higher risk to develop diabetes than those with ‘normal type'. Those with low insulinogenic index (the ratio of increment of plasma insulin to that of plasma glucose at 30min of OGTT) are at particularly higher risk to develop diabetes. Diabetes-specific microvascular complications are rare but arteriosclerotic complications are fairly frequent in this category. Gestational diabetes mellitus (GDM) : The current definition of GDM is “any glucose intolerance developed or detected during pregnancy”. We adopt the proposal of the Japan Society of Gynecology and Obstetrics for the diagnosis of GDM (1984). GDM is defined when two or more values of the following points at 75g OGTT are higher than the cutoff levels ; FPG ≧ 100mg/dl, 1 hPG ≧ 180 mg/dl and 2 hPG ≧ 150mg/dl. As a screening test, casual plasma glucose is to be measured at first visit of pregnancy, and if it exceeds 100mg/dl, the subject should be tested by OGTT. Patients who have had glucose intolerance since pregestational period, and who have been presented as ‘diabetic type', should be under closer supervision than those who become GDM during pregnancy for the first time. HbA1C : There is a large overlap in the distribution of HbA1C between groups with ‘normal type' and ‘borderline type' and mild ‘diabetic type'. Therefore, HbA1C is not a suitable parameter to detect mild glucose intolerance. As stated before, HbA1C higher than 6.5% suggests diabetes, but HbA1C below 6.5% alone should not be regarded as an evidence against the diagnosis of diabetes. © 1999, THE JAPAN DIABETES SOCIETY. All rights reserved.