Diagnostic Criteria of Diabetes Mellitus Basil OM Saleh

Objectives

1. Definition 2. Terminology 3. Glycated Hemoglobin HbA1c 4. Normal Plasma Glucose Level Should be Defined •ADA & WHO criteria 5. Criteria for Testing for Diabetes in Asymptomatic Adult Individuals 6.Tests to Diagnose Diabetes 7. Advantages and disadvantage of assays for glucose and HbA1c

8. Diabetes in children

Definition:

The term diabetes mellitus (D M) describes several diseases of abnormal carbohydrate metabolism that are characterized by hyperglycemia. It is associated with a relative or absolute impairment in insulin secretion, along with varying degrees of peripheral resistance to the action of insulin.

D M is associated with reduced life expectancy and significant morbidity due to specific diabetes related microvascular & macrovascular complications.

Every few years, the diabetes community reevaluates the current recommendations for the classification, diagnosis, and screening of diabetes, reflecting new information from research and clinical practice.

TERMINOLOGY

The 1997 ADA Expert Committee introduced the terms type 1 and type 2 diabetes, and recommended against terms like insulin-dependent and noninsulin-dependent. Also "specific types“ •gestational diabetes •diabetes of genetic defects •diseases of the exocrine pancreas & other endocrinopathies •drugs

Glycated hemoglobin (HbA1c) • reflects average plasma glucose over the previous eight to 12 weeks •It can be performed at any time of the

day and does not require any

special preparation such as fasting. •The use of HbA1c can avoid the problem of day-to-day variability of glucose values

It established a validated relationship between A1C and average glucose across a range of diabetes types and patient

populations.

HbA1c was introduced into clinical use in the 1980s and subsequently has become a cornerstone of clinical practice.

Recent estimates indicate there were 171 million people/world in 2000 with diabetes 366 million by 2030. Should normal plasma glucose levels be defined? ADA and WHO criteria ADA defined a normal FSG •as 110 mg/dl in 1997 •as 100 mg/dl in 2003 & a normal 2–h plasma glucose as 11.1mmol/l (200 mg/dl) are present. .

Levels of HbA1c just below 6.5% may indicate the presence of intermediate hyperglycaemia. The precise lower cut-off point for this has yet to be defined, although the ADA has suggested 5.7 – 6.4% as the high risk range.

WHO recommended High risk of diabetes HbA1c (6.0 – 6.4%) Provide intensive lifestyle advice. Warn patients to report symptoms of diabetes. Monitor HbA1c annually. HbA1c 25 Kg/m2) and have additional risk factors: •history of CVD •first degree relative with D •PCOS •HDL-C< 35 mg/dl or TG≥250 mg/dl •HTN≥140/90 or on meds •A1c≥5.7%, IGT or IFG •delivered baby>9 Ibs, GDM •habitual physical inactivity. 2. In the absence of the above risk, start testing for diabetes at age 45. 3. If results normal, repeat test at 3 year intervals or more frequently depending on risk

Tests to Diagnose Diabetes-Table 2 For all the below tests, in the absence of unequivocal hyperglycemia, results should be confirmed by repeat testing

STAGE

HbA1c

FSG (No intake 8 hrs.)

Diabetes

A1c> 6.5 %

FSG > 126 RSG > 200 Two-hour mg/dl mg/dl plus SG(2hSG) > symptoms 200 mg/dl

Increased risk of Diabetes

A1c 5.76.4 %

IFG = 100125 mg/dl

IGT= 2hSG 140-199 mg/dl

FSG < 100 mg/dl

2hSG < 140 mg/dl

Normal

A1c < 5.7 %

RSG

(OGTT)75g

Recommendations For The Diagnosis And Classification Of Diabetes Mellitus 2012 GESTATIONAL DIABETES (GDM)

SCREENING

TEST

DIAGNOSIS CRITERIA

At the first prenatal visit, screen for undiagnosed type 2 in those w/ risk factors as listed in Table 1

Standard Diagnostic Testing and Criteria as listed in Diagnosing Diabetes –Table 2

Standard Diagnostic Testing and Criteria as listed in Diagnosing Diabetes –Table 2

Screen for GDM at 24– 28 weeks of gestation for all pregnant women not known to have diabetes. Screen women w/ GDM for diabetes 6-12 wks postpartum

Perform a 75-g OGTT, with plasma glucose measurement fasting and at 1 and 2 h. The OGTT should be performed in morning after an overnight fast of at least 8 h.

The diagnosis of GDM is made when ANY of following BG values are exceeded: Fasting ≥92 mg/dl 1 h ≥180 mg/dl 2 h ≥153 mg/dl

However there are •100-gr glucose load with plasma glucose measurement over 1 hr., 2 hr., and 3 hr. •simple and first step evaluation of suspected GDM by 50-gr glucose load with PG estimation after 1 hr. without regarding to fasting state. Pregnant women are categorized as low, intermediate and high risk GDM.

Some of the factors that influence HbA1c and its measurement.

1. Erythropoiesis Increased HbA1c: iron, vitamin B12 deficiency, decreased erythropoiesis. Decreased HbA1c: administration of erythropoietin, iron, vitamin B12, reticulocytosis, chronic liver disease.

2. Altered Haemoglobin Genetic or chemical alterations in haemoglobin: haemoglobinopathies,HbF,

3. Glycation

Increased HbA1c: alcoholism, chronic renal failure Decreased HbA1c: aspirin, vitamin C and E, certain haemoglobinopathies,

4. Erythrocyte destruction

Increased HbA1c: increased erythrocyte life span: Splenectomy. Decreased A1c: decreased erythrocyte life span:

5. Assays

Increased HbA1c: hyperbilirubinaemia, carbamylated haemoglobin, alcoholism, large doses of aspirin, chronic opiate use. Variable HbA1c: haemoglobinopathies. Decreased HbA1c: hypertriglyceridaemia.

Advantages and disadvantage of assays for glucose and HbA1c

Glucose

HbA1c

Patient preparation prior to collection of blood Processing of blood

Stringent requirements if measured for diagnostic purposes.

None.

Stringent requirements for rapid processing, separation and storage of plasma or serum minimally at 4°C.

Avoid conditions for more than 12hr at temperatures >23C. Otherwise keep at 4C (stability minimally 1 week).

Measurement

Widely available

Not readily available worldwide

Interferences: illness

Severe illness may increase Severe illness may shorten glucose concentration red-cell life and artifactually reduce HbA1c values

Haemoglobinopa Little problem unless the patient is ill. -thies

May interfere with measurement in some assays.

Diabetes

in

children

Diabetes in children usually presents with severe symptoms, very high blood glucose levels, marked glycosuria, and ketonuria. In most children the diagnosis is confirmed without delay by blood glucose measurements, and treatment

(including insulin injection) is initiated immediately, often as a life–saving measure. An OGTT is neither necessary nor appropriate for diagnosis in such circumstances (glucose load is weight dependent; (1.75 g/Kg).

The new criteria have simplified the diagnosis of diabetes and the ability to diagnose cardiovascular complications. Earlier diagnosis will increase the total number of people with diabetes, but if they are carefully managed, many of these new cases will be diet controlled. In the long term, complications should be lessened to the benefit of the individual and to the health service.

SUMMARY

D M is a group of metabolic disorders of CHO metabolism in which glucose is underutilized, producing hyperglycemia . Diabetes and lesser forms of glucose intolerance, IGT and IFG, can now be found in almost every population in the world and epidemiological evidence suggests that, without effective prevention and control programmes, the burden of diabetes is likely to continue to increase globally

References

•Use of Glycated Hemoglobin (HbA1c) in the Diagnosis of Diabetes Mellitus. World Health Organization 2011. •Definition and diagnosis and Classification of Diabetes Mellitus and its Complications Report of a WHO Consultation Part 1: Diagnosis and Classification of Diabetes Mellitus