Diagnosing Diabetes, Pre-Diabetes And The Metabolic Syndrome Indications for Screening
All those who complain of symptoms or show signs commonly associated with diabetes must have a test for diabetes. Many people do not manifest typical signs or symptoms commonly associated with T2DM and therefore, if feasible, all persons over the age of 25 years should undergo an annual test to rule out the presence of diabetes.
Persons at high risk MUST undergo testing when they present for medical attention for whatever reason, and if negative, must have a regular check, thereafter.
For a list of people who would be at high risk for T2DM, see Appendix 1a
It should always be remembered that
A negative test for diabetes does NOT mean that the person will never get diabetes. It only means that the person does NOT have diabetes at the time of testing.
In the occasional patient, especially those manifesting characteristic signs and symptoms of diabetes, one may be able to diagnose diabetes based on the result of a single sample of blood.
In a patient with characteristic sign and symptoms of diabetes, a fasting venous plasma glucose > 126 mg%(7.0 mmol per L), OR a random venous plasma glucose > 200 mg% (11.1 mmol per L), confirmed on repeat testing, is diagnostic. negative test for diabetes does NOT mean that the person will never get diabetes. It only means that the person does NOT have diabetes at the time of testing.
Method
Urine examination for the presence of sugars should NEVER be the method to diagnose diabetes.
The only presently accepted way of analysing blood for glucose is to use to Glucose Oxidase method. It is also important to note whether the laboratory, even though using the glucose oxidase method, uses capillary blood, whole venous blood, or venous plasma for the estimation. The levels of glucose in plasma are about 15% higher than the levels in whole blood and the diagnostic criteria differ. Unless one is aware of this, one will not be able to accurately interpret the results.
Although the American Diabetes Association (ADA) feels that just a fasting plasma glucose level should be adequate to diagnose diabetes, the World Health Organization (WHO) has not given up the Glucose Tolerance test (OGTT).
For a detailed note on the procedure for carrying out an OGTT, see Appendix 1b
Criteria For Diagnosis
TABLE 1
| Glucose Concentration mg/100ml (mmol/l) | ||||
| Whole Blood | Plasma | |||
| Venous | Capillary | Venous | Capillary | |
| Diabetes Mellitus | ||||
| Fasting or | >/=110 (6.1mmol/l) | >/=110 (6.1mmol/l) | >/=126 (7 mmol/l) | >/=126(7 mmol/l) |
| 2 hours post Glucose Load or both | >/=180 (10.0mmol/l) | >/=200 (11.1mmol/l) | >/=200 (11.1mmol/l) | >/=220 (12.2 mmol/l) |
| Impaired Glucose Tolerance | ||||
| Fasting (If measured) | <110 (< 6.1mmol/l) | <110 (< 6.1mmol/l) | <126 (< 7 mmol/l) | <126(< 7 mmol/l) |
| 2 hours post Glucose Load | >/=120 & <180(>/= 6.7 mmol/l & < 10 mmol/l) | >/=140 & <200(>/= 7.8 mmol/l & < 11.1 mmol/l) | >/=140 & <200(>/= 7.8 mmol/l & < 11.1 mmol/l) | >/=160 & <220(>/= 8.9 mmol/l & < 12.2 mmol/l) |
| Impaired Fasting Glycemia | ||||
| Fasting | >/=100 & <110(>/= 5.6 mmol/l & < 6.1 mmol/l) | >/=100 & <110(>/= 5.6 mmol/l & < 6.1 mmol/l) | >/=110 & <126(>/= 6.1 mmol/l & <7.0 mmol/l) | >/=110 & <126(>/= 6.1 mmol/l & <7.0 mmol/l) |
| 2 hours PG (If measured) | <120 (< 6.7 mmol/l) | <140 (< 7.8 mmol/l) | <140 (< 7.8 mmol/l) | <160 (< 8.9 mmol/l) |
Many patients are diagnosed using blood glucose meter readings especially in epidemiological surveys. Most of the modern meters are callibrated to give the equivalent plasma glucose readings. In the fasting state this does correlate with the venous plasma glucose levels. But NOT in the non fasting state! When used to evaluate the 2 hours postglucose results, it would be better to use the capillary plasma glucose values for diagnostic purposes.
The diagnosis of diabetes made by a using a meter should always be confirmed by repeat testing on another day, preferably in a laboratory, unless there is unequivocal hyperglycemia or obvious symptoms.
Most people tested would show “normal” values.
But,
"A NEGATIVE TEST RESULT ONLY SHOWS THAT THE PERSON DOES NOT HAVE DIABETES AT THE TIME OF TESTING. IT DOES NOT MEAN THAT THE PERSON WILL NEVER GET DIABETES IN THE FUTURE. WHICH IS WHY AN ANNUAL CHECKUP IS ESSENTIAL”
Pre-Diabetes
Patients with IFG and/or IGT are now referred to as having “pre-diabetes” indicating the relatively high risk for future diabetes as well as cardiovascular disease. IFG and IGT are associated with the metabolic syndrome, which includes obesity (especially abdominal or visceral obesity), atherogenic dyslipidemia, and hypertension. The presence of these metabolic disorders would warrant specific treatment even if the patients are being monitored for the future development of diabetes.
The Metabolic Syndrome
The metabolic syndrome is a cluster of risk factors which predispose a person to Type 2 diabetes mellitus (T2DM) and atherosclerotic cardiovascular disease (ASCVD). Its presence confers a two fold increase in the risk for major CVD events and a five fold increase in the life time risk for T2DM.
The two most widely utilized diagnostic definitions are those of the International Diabetes Federation (IDF) and the AHA/NHLBI (updated ATP-III). (Table 2)
Table 2
| IDF clinical criteria for metabolic syndrome | AHA/NHLBI diagnostic criteria for metabolic syndrome | ||
| Measure (central obesity sine qua non plus any two of four other criteria constitute a diagnosis of metabolic syndrome) | Categorical cut points | Measure (any three of the five criteria below constitute a diagnosis of metabolic syndrome) | Categorical cut points |
| Central obesity | Waist circumference ethnic specific (80 cm for women) for Indian subjects | Elevated waist circumference | General U.S. population: 102 cm (40 in) in men, 88 cm (35 in) in women; lower cut points for insulin-resistant individuals or ethnic groups (based on clinical judgment). |
| Raised triglycerides | >150 mg/dl (1.7 mmol/l) or on specific treatment for this lipid disorder | Elevated triglycerides | ≥ 150 mg/dl (1.7 mmol/l) or on drug treatment for elevated triglycerides |
| Reduced HDL cholesterol | <40 mg/dl (1.0 mmol/l) in men, <50 mg/dl (1.3 mmol/l) in women or on specific treatment for reduced HDL-C |
Reduced HDL cholesterol | <40 mg/dl (1.0 mmol/l) in men, <50 mg/dl (1.3 mmol/l) in women or on specific treatment for reduced HDL-C |
| Raised blood pressure | < 130 mmHg systolic blood pressure or 85 mmHg diastolic blood pressure or on treatment for previously diagnosed hypertension | Elevated blood pressure | 85 mmHg diastolic blood pressure or on drug treatment for previously diagnosed hypertension |
| Elevated fasting plasma glucose | Fasting plasma glucose 100 mg/dl (5.6 mmol/l) or on treatment for previously diagnosed type 2 diabetes | Elevated fasting plasma glucose | 100 mg/dl (5.6 mmol/l) or or on treatment for previously diagnosed type 2 diabetes |
Table 2. Diagnostic criteria for metabolic syndrome from the International Diabetes Federation (IDF) definition and the American Heart Association (AHA)/National Heart, Lung, and Blood Institute (NHLBI) (updated ATP-III) definition.
The IDF asks for an increase in central obesity as measured by the waist measurement as a definite requirement for the diagnosis of the metabolic syndrome. The NHLBI, although using waist measure criteria which is focused on their population has also accepted that people of different ethnic origins may require different individualized waist measures.
The method to measure the waist circumference and Country/Ethnic group specific diagnostic waist circumference measures in given in Appendix 1c
Once a person has been diagnosed as having diabetes, they need NEVER undergo a Glucose Tolerance Test. This test is only for diagnosis.
To sum up,
Once a person is diagnosed to have diabetes, he or she must be thoroughly investigated for the presence of other components of the Metabolic Syndrome, such as hypertension, lipid abnormalities, weight characteristics, especially central obesity, presence of cardiovascular disease, novel risk factors and for the presence of the long term diabetic complications.
As importantly, just because a person is not diagnosed as having the Metabolic Syndrome, due to the absence of central obesity or the absence of two of the other factors, does not mean that the presence of any of the risk factor by itself should NOT be treated!