Hba1c glycosylated hemoglobin imam.pptx

HbA1c

1. Glycosylated hemoglobin HbA1c dr. Imam Manggalya dr. R. Bowo Pramono , Sp.PD -KEMD

2. Hemoglobin HbA0(α2 ß2) 90 % HbA1 HbA1c HbA2(α2δ2) HbF(α2γ2) Non ezymatically glycosylated form of human hemoglobin, taking place under physiological conditions, at a specific site on the protein

3. Terminology • Hb: hemoglobin • HbA1: is a series of glycated variants resulting from attachment of various carbohydrates to N terminal valine of Hb • Glycation results in increased negative charge and hence runs fast on electrophoresis systems Pickup & Williams , Textbook of Diabetes

4. GHb: glycated hemoglobin 1. HbA1a1: fructose 1,6 diphosphate N terminal valine 2. HbA1a2: glucose 6 phosphate N terminal valine 3. HbA1b: unknown carbohydrate N terminal valine 4. HbA1c: (60-80%): attachment of glucose to N terminal amino acid valine of the beta chain of hemoglobin Total glycated Hb: HbA1c+ sugar Non N terminal sites

5. Relationship of glycemic control and diabetes duration to diabetic retinopathy . The Diabetes Control and Complications Trial Research Group, Diabetes 44:968, 1995

6. Relationship of HbA 1C to Risk of Microvascular Complications Diabetes Control and Complications Trial (DCCT) 15 13 11 9 7 5 3 1 6 7 8 9 10 HbA 1C (%) Skyler JS. Endocrinol Metab Clin North Am. 1996;25:243-254. Retinopathy Nephropathy Neuropathy Microalbuminuria 11 12

7. Slide 7 DCCT Trial (Type 1 diabetes): Microvascular complications increase as HbA 1c increases 30 20 10 2 4 6 8 10 Patients (%) Year Microalbuminuria*: 34% reduction Retinopathy: 76% reduction Patients (%) 60 40 20 2 4 6 8 10 Conventional Intensive *Urinary albumin excretion ≥40 mg per 24 hours Adapted from: DCCT. N Engl J Med 1993;329:977–86 Year Intensive Conventional

8. Slide 8 Risk of Complications increases as Hb1Ac increases and that’s why diabetes must be treated Stratton IM et al. BMJ 2000;321:405 – 12 Myocardial infarction Microvascular disease Adjusted for age, sex, and ethnic group. The relationship between A1C and mg/dl is described by the formula 28.7 X A1C – 46.7 = mg/dl. Incidence per 1.000 patient-years 126 97 154 183 212 240 269 Mean HbA1c (%) Mean mg/dl

9. Slide 9 The benefits of good blood glucose control are clear Good control is ≤ 7.0% HbA 1c HbA 1c measures the average blood glucose level over the last three months Source: UKPDS = United Kingdom Prospective Diabetes Study. Stratton IM et al. BMJ. 2000;321(7258):405-412. Deaths related to diabetes Microvascular complications Myocardial infarction -14% -37% -21% HbA 1c -1%

10. Slide 10 What is good glycemic control? Overall aim to achieve glucose levels as close to normal as possible Minimise development and progression of microvascular and macrovascular complications FPG <130 mg/dL HbA 1c < 7.0% PPG <180 mg/dL FPG <110 mg/dl HbA 1c < 6.5% PPG <145 mg/dL IDF 2 ADA 1 PERKENI 3 1. American Diabetes Association Diabetes Care 2009;32 (Suppl 1):S1-S97 2. IDF Clinical Guidelines Task Force. International Diabetes Federation 2005. 3. PERKENI 2011 Konsensus . FPG <100 mg/dl HbA 1c < 7% PPG <140 mg/dl

11. Factors affecting HbA1c Falsely elevated values • HbF or HbG • Uremia ( BUN > 85 mg/dl) • Hypertriglyceridemia( cation exchange +, EP-) • Alcohol • High bilirubin( cation exchange+, HPLC+) • Aspirin • Splenectomy, Aplastic anemia

12. Factors affecting HbA1c Falsely low HbA1c • HbC, HbS • Hemolytic anemias • Pregnancy • Acute/ Chronic blood loss • Vitamin E/C • Dapsone • Severe nephropathy ( shorten RBC survival) Glycated hemoglobin monitoring BMJ 2006 ; 333;586-8

13. What does HbA1c represent ?

14. Patients with variable diurnal profiles can have the same A1c Roger Mazze DIABETES TECHNOLOGY & THERAPEUTICS Volume 10, Supplement 1, 2008

15. Relationship between FPG, PPG and HbA1c 80 Postprandial Fasting Hyperglycemia 60 40 20 1 2 3 4 5 (<7.3) (7.3-8.4) (8.5-9.2) (9.3-10.2) (>10.2) HbA 1c quintiles Monnier L, Diabetes Care 2003;26

16. ADAG study A1c Derived Average Glucose • Define the mathematical relationship between A1c and average glucose levels • 507 subjects : 268 with type 1 diabetes, 159 with type 2 diabetes and 80 non diabetic subjects • A1c at end of 3 months compared with average glucose during the previous 3 months • From 2 day CGMS 4 times+7 point SMBG 3 times/week Nathan D Diabetes Care 31:1-6, 2008

17. ADAG study • Approx 2700 values/subject in 3 months • Linear regression analysis between A1c and AG values provided the tightest correlations AG (mg/dl) = 28.7X A1C-46.7 ( R2 0.84, P 0.0001)

18. ADAG study Estimated average glucose ( e AG) mg/dl Nathan D Diabetes Care 31:1-6, 2008 mmol/L DCCT 135 170 205 240 275 310

19. Hba1c represents more recent sugars

20. Mean blood sugars vs. ADAG ADAG MBG ADAG : A1c Derived Average Glucose

21. Methods of measuring HbA1c • Ion exchange chromatography : low pressure HPLC • Electrophoretic methods • Immunoturbimetric methods • Affinity methods • Chemical methods: e.g thiobarbituric method • Electrospray iontophoresis • Mass spectroscopy • Reversed phase HPLC

22. Methods for HbA1c The better and best Electrospray iontophoresis Mass spectrometry HPLC CV : 2-3 % Immunoassay methods CV 5-6 % •Point of care ( POC) Instruments • Colorimetry

23. Can we use HbA1c for diagnosis of diabetes ?

24. Cut offs Fasting plasma glucose cut offs for definition of IGT and DM Normal IGT Type 2 diabetes 100 mg/dl 126 mg/dl

25. Diagnosis of diabetes • Diagnosis of diabetes has always been glucose centric : based on FBS, 2 hr post glucose , RBS • National Diabetes Data Group (NDDG) 1979 : relied on distributions of glucose levels • Based on their association with decompensation to “overt” or symptomatic diabetes FPG > 140 mg/dl PPG > 200 mg/dl

26. FPG/PPG /HbA1c vs. Retinopathy U.S. National Health and Nutrition Examination Survey (NHANES) population ( n 2,821)

27. Current use of HbA1c • Monitor long term glycemic control • Adjust therapy • Assess the quality of diabetes care • Predict the risk for the development of complications

28. HbA1c for diagnosis of diabetes • HbA1c correlates with retinopathy • There was a stronger correlation between A1C and retinopathy than between fasting glucose levels and retinopathy • Similar correlation between A1c and Retinopathy has been seen in DCCT/ UKPDS trials • 1997 Expert Committee recommended against using A1C values for diagnosis in part because of the lack of assay standardization

29. 2009 :International Expert Committee Report on the Role of the A1C Assay in the Diagnosis of Diabetes DIABETES CARE, VOLUME 32, NUMBER 7, JULY 2009 Recommends that HbA1c be adopted as one of the diagnostic criteria for diabetes

30. Pitfalls with glucose measurement • The measurement of glucose itself is less accurate and precise than most clinicians realize • 41% of instruments have a significant bias from the reference method that would result in potential misclassification of 12% of patients • Potential preanalytic errors owing to sample handling • Lability of glucose in the collection tube at room temperature International Expert Committee Report on the Role of the A1C Assay in the Diagnosis of Diabetes. DIABETES CARE, VOLUME 32, NUMBER 7, JULY 2009

31. Advantages of HbA1c • HbA1c is stable after collection • New reference method to calibrate all A1C assay instruments should further improve A1C assay standardization in most of the world between- and within-subject • Coefficients of variation have been shown to be substantially lower for A1C than for glucose measurements • The variability of A1C values is also considerably less than that of FPG levels, with day-to-day within-person variance of 2% for A1C but 12-15% for FPG International Expert Committee Report on the Role of the A1C Assay in the Diagnosis of Diabetes. DIABETES CARE, VOLUME 32, NUMBER 7, JULY 2009

32. Advantages of HbA1c • Convenience for the patient and ease of sample collection for A1C testing • Relatively unaffected by acute (e.g., stress or illness related) perturbations in glucose levels International Expert Committee Report on the Role of the A1C Assay in the Diagnosis of Diabetes. DIABETES CARE, VOLUME 32, NUMBER 7, JULY 2009

33. Cut off of HbA1c for diagnosis of diabetes • Cut offs at which the prevalence of retinopathy increases • NHANES data and DETECT 2 study

34. DETECT 2 study Prevalence of retinopathy by 0.5% intervals and severity of retinopathy in participants aged 20-79 years. NPDR, nonproliferative diabetic retinopathy. Adapted with permission from (S.C., personal communication). 19,000 subjects from nine countries The glycemic level at which the prevalence of “any” retinopathy begins to rise above background levels and for the more diabetes-specific “moderate” retinopathy, was 6.5% when the data were examined in 0.5% increments

35. Cut off of HbA1c • A1C level of 6.5% is sufficiently sensitive and specific to identify individuals who are at risk for developing retinopathy and who should be diagnosed as diabetic • A1C level is at least as predictive as the current FPG and 2HPG values.

36. “ Prediabetes” • Once A1c is used to diagnose diabetes, “ prediabetes” or IGT/ IFG may be obsolete • HbA1c between 6 and 6. 5 % : higher risk for developing diabetes more effective interventions

37. Practical considerations • POC instruments are not to be used to make this diagnosis • Always confirm using the same tests • Intermethod variability is reported to still be a potential source of inaccuracy

38. Words of wisdom • HbA1c and mean glucose corroborate abnormal glucose metabolism, but it requires self monitoring ( or CGMS) to detect the location and magnitude of the abnormalities • HbA1c and SMBG should be considered together, with each complementing the information provided by the other Peacock I J Clin Path 1984

39. Thank you

40. H i gh e r ri s k of h y pog l y c emi a • • • • A g e > 65 y e ars Long e r du rat io n H igh e r H b A1c U s e o f in s uli n o f in s uli n u s e • • • • U s e o f S U Old e r a g e R e n al dy s fun c t ion , M e n tal h e a l th i ss u es , ( e .g . d e m e n t i a)