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Diagnosis & Diagnostic Tests of Diabetes

Diagnosis & Diagnostic Tests of Diabetes:<br>To screen, detect or monitor diabetes.

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Diagnosis & Diagnostic Tests of Diabetes

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  1. Diagnosis & Diagnostic Tests of Diabetes Dr Shahjada SelimAssociate ProfessorDepartment of Endocrinology, BSMMU • Visiting Professor in Endocrinology, Texila American University, USAWebsite: shahjadaselim.com

  2. Diagnostic Tests for Diabetes 1. Oral Glucose Tolerance Test (OGTT) 2. Glycated Hemoglobin (HbA1C) 3. Glycated Albumin 4. Fructosamine assay 5. Insulin Assay 6. Proinsulin Assay 7. C-Peptide Assay

  3. Glucose Tolerance Test [GTT] A glucose tolerance test is the administration of glucose in a controlled and defined environment to determine how quickly it is cleared from the blood. The test is usually used to test for diabetes, insulin resistance, and sometimes reactive hypoglycemia. The glucose is most often given orally.

  4. Standard Oral glucose tolerance test • I/V Glucose tolerance test • Mini Glucose tolerance test Types of GTT

  5. In asymptomatic persons with sustained or transient glycosuria. • In persons with symptoms of diabetes but no glycosuria or hyperglycemia. • Persons with family history but no symptoms or positive blood findings. • In persons with or without symptoms of diabetes mellitus showing one abnormal blood findings. • In patients with neuropathies or retinopathies of unknown origin. Indication of OGTT

  6. There is no indication for doing GTT in a person with confirmed diabetics mellitus. • GTT has no role in follow-up of diabetics. • The test should not be done in ill patients. Contraindications of glucose tolerance test

  7. Patient should be on unrestricted carbohydrate diet for 3 days. • Patient should be ambulatory with normal physical activity. • Medications should be discontinued on the day of testing. • Exercise, smoking and tea or coffee are not allowed during test period. • OGTT carried out in the morning after patient has fasted overnight for 8-12 hours. Preparation of patient

  8. Limitations of OGTT • The OGTT is less accurate than the hyperinsulinemic-euglycemic clamp technique (the "gold standard" for measuring insulin resistance), or the insulin tolerance test, but is technically less difficult. Neither of the two technically demanding tests can be easily applied in a clinical setting or used in epidemiological studies. • HOMA-IR (homeostatic model assessment) is a convenient way of measuring insulin resistance in normal subjects, which can be used in epidemiological studies, but can give erroneous results for diabetic patients.

  9. Test A fasting venous blood sample is collected in the morning. Patients ingest 75 g of anhydrous glucose in 250-300 ml of water over 5 minutes. ( for children, the dose is 1.75 g of glucose per kg).

  10. In the classical procedures, the blood and urine samples are collected at half hourly interval of the next three hours. • A curve is plotted with the blood glucose levels on the vertical axis against the time of collection on the horizontal axis. • The curve so obtained is called glucose tolerance curve. Test

  11. Acute infections- Cortisol is secreted, the curve is elevated and prolonged. • Hypothyroidism-A flat curve is obtained in hypothyroidism. Thyroid hormone increases the absorption of glucose from the gut. • Starvation- There is rise of counter regulatory hormones, which show increased glucose tolerance. Factors affecting GTT

  12. A1C ≥6.5% * Performed in a laboratory using a method that is NGSP certified and standardized to the DCCT assay - www.ngsp.org POC testing not recommended Greater convenience, preanalytical stability, and less day-to-day perturbations than FPG and OGTT Consider cost, age, race/ethnicity, anemia, etc. American Diabetes Association Standards of Medical Care in Diabetes. Classification and diagnosis of diabetes. Diabetes Care 2019; 39 (Suppl. 1): S13-S22

  13. Glycated Hemoglobin Hemoglobin + glucose Aldimine Glycated hemoglobin Glycated hemoglobin covers a number of chemically different modification resulting from the non-enzymatic and irreversibly binding of different sugars to different amino groups in the hemoglobin molecule. (Maillard Reaction )

  14. HbA₁с gives information about the average blood glucose concentration over a retrospective period of time. • Reflects the mean glucose concentration. • Normally, less than 5% of hemoglobin is glycated. Glycated hemoglobin

  15. About 50% HbA₁с values results from the blood glucose of the preceding 30 days , 40% from the preceding 31- 90 days and only 10% from the period between the 91 – 120 days. • No effect of diet, exercise & insulin on test results. • More informative. Glycated hemoglobin

  16. Diagnostic Testing With 3 Different Tests • Dealing with Discordance • Many people identified as having diabetes using A1C will not be identified as having diabetes by traditional glucose criteria, and vice versa. FPG 2hPG A1C • When results of more than one test are available (amongst FPG, A1C, 2hPG in a 75-g OGTT) and the results are discordant, the test whose result is above diagnostic cut-point should be repeated, and the diagnosis made on basis of the repeat test.

  17. In all diabetes to monitor long term blood glucose level control, index of diabetic control: 7% HbA₁с – good 10% HbA₁с- Poorly ontrolled > 13% HbA₁с- Very poor control. • To monitor patient compliance. INDICATIONS

  18. To predict development & progression of microvascular complication. • For determining the therapeutic option whether to use oral agents, insulin or β cell transplantation. • Also increasingly used for primary diagnosis of DM. INDICATIONS

  19. At what interval should HbA₁с be determined?

  20. Glycated hemoglobin

  21. Glycated hemoglobin

  22. Do not Do HbA1c in… In conditions associated with an altered relationship between A1C and glycemia, such as sickle cell disease, pregnancy (2nd and 3rd trimesters and the postpartum period), glucose-6-phosphate dehydrogenase deficiency, HIV, hemodialysis, recent blood loss or transfusion, or erythropoietin therapy, only plasma blood glucose criteria should be used to diagnose diabetes.

  23. Blood sample can be drawn at any time of day. • HbA1c of 6 % corresponds to mean serum glucose level of 7.5 mmol/L (135 mg/dl). • With every rise of 1.0%, serum glucose increases by 35 mg/dl. HbA1C

  24. Fructosamine assay Generic term for measurement of all serum glycated protein though the bulk being albumin. Does not appear to be influenced by transient (stress) hyperglycemia. Unable to detect short term or transient abnormalities in the blood glucose concentration. Ex: hypoglycemia. Reference range – in non diabetic- 2.4-3.4 mmol/l. Fructosamine / albumin ratio:- 54- 86 µmol/gm.

  25. Fructosamine assay

  26. Half -life of albumin is approximately 15 days. • Glycated albumin level is believed to reflect the glycemic change over a 2-week period. • GA can be useful in evaluating the therapeutic effect of recently substituted hypoglycemic agents at an early stage. Glycosylated Albumin

  27. GA can also act as a valuable glycemic control marker in diabetic patients with various comorbidities since it is unrelated to the metabolism of hemoglobin. Glycosylated Albumin

  28. Insulin assay Measurement of insulin level by radioimmunoassay & ELISA. Crucial for type I DM.

  29. It is precursor molecule for insulin. • Most proinsulin is converted to insulin and C-Peptide, which are secreted in equimolar amounts into the blood. • The biological activity of proinsulin is only about 10% of insulin, but the half life of proinsulin is three times as long as insulin. Proinsulin Assay

  30. Elevated in: • At onset of T1DM and in healthy sliblings of T1DM patients. • With established T2DM. • Older patients. • Pregnant . • Obese pt with diabetes. • Insulinomas. • Functional hypoglycemia. • Hyperinsulinemia. Proinsulin Assay

  31. C peptide assay Released in circulation during conversion of proinsulin to insulin in equimolar quantities to insulin. Its level correlate with insulin level in blood. Low C – peptide levels are characteristic of type I DM. C-peptide levels are measured instead of insulin levels because C- peptide can assess a person’s own insulin secretion even if they receive insulin injections.

  32. C peptide assay The test may be used to help determine the cause of hypoglycemia, values will be low if a person has taken an overdose of insulin but not suppressed if hypoglycemia is due to an insulinomas.. Factitious hypoglycemia may occur secondary to the surreptitious use of insulin. Measuring C-peptide levels will help differentiate a healthy patients from a diabetes one.

  33. Recommendations: T1DM Blood glucose rather than A1C should be used to diagnose T1DM in symptomatic individuals. E Screening for T1DM with an antibody panel is recommended only in the setting of a clinical research study or in a first-degree family members of a proband with type 1 diabetes. www.DiabetesTrialNet.org American Diabetes Association Standards of Medical Care in Diabetes. Classification and diagnosis of diabetes. Diabetes Care 2020; 40 (Suppl. 1): S11-S24

  34. Recommendations

  35. Recommendations: Testing for Type 2 Diabetes Screening for T2DM with an informal assessment of risk factors or validated tools should be considered in asymptomatic adults. Consider testing in asymptomatic adults of any age with BMI ≥25 kg/m2 or ≥23 kg/m2 in Asian Americans who have 1 or more additional DM risk factors. For all patients, testing should begin at age 45 years. If tests are normal, repeat testing carried out at a minimum of 3-year intervals is reasonable. American Diabetes Association Standards of Medical Care in Diabetes. Classification and diagnosis of diabetes. Diabetes Care 2020; 40 (Suppl. 1): S11-S24

  36. Screening for Type 2 Diabetes (2) FPG, 2-h PG after 75-g OGTT, and the A1C are equally appropriate. In patients with diabetes, identify and, if appropriate, treat other CVD risk factors. Consider testing for T2DM in overweight/obese children and adolescents with 2 or more additional diabetes risk factors. American Diabetes Association Standards of Medical Care in Diabetes. Classification and diagnosis of diabetes. Diabetes Care 2020; 40 (Suppl. 1): S11-S24

  37. Criteria for the Diagnosis of Diabetes American Diabetes Association Standards of Medical Care in Diabetes. Classification and diagnosis of diabetes. Diabetes Care 2020; 40 (Suppl. 1): S11-S24

  38. Recommendations: Prediabetes Testing should begin at age 45 for all patients, particularly those who are overweight or obese. American Diabetes Association Standards of Medical Care in Diabetes. Classification and diagnosis of diabetes. Diabetes Care 2019; 39 (Suppl. 1): S13-S22

  39. Recommendations: Prediabetes (2) FPG, 2-h PG after 75-g OGTT, and A1C, are equally appropriate for prediabetes testing. In patients with prediabetes, identify and, if appropriate, treat other CVD risk factors. Consider prediabetes testing in overweight/obese children and adolescents with 2 or more additional diabetes risk factors. American Diabetes Association Standards of Medical Care in Diabetes. Classification and diagnosis of diabetes. Diabetes Care 2019; 39 (Suppl. 1): S13-S22

  40. Prediabetes* * For all three tests, risk is continuous, extending below the lower limit of a range and becoming disproportionately greater at higher ends of the range. American Diabetes Association Standards of Medical Care in Diabetes. Classification and diagnosis of diabetes. Diabetes Care 2020; 39 (Suppl. 1): S13-S22

  41. Recommendation: Screening for Type 1 Diabetes Blood glucose rather than A1C should be used to dx type 1 diabetes in symptomatic individuals. American Diabetes Association Standards of Medical Care in Diabetes. Classification and diagnosis of diabetes. Diabetes Care 2020; 39 (Suppl. 1): S13-S22

  42. Recommendations: Screening for Type 2 Diabetes (2) For all people, testing should be begin at age 45 years. B If tests are normal, repeat testing carried out at a minimum of 3-year intervals is reasonable. C American Diabetes Association Standards of Medical Care in Diabetes. Classification and diagnosis of diabetes. Diabetes Care 2019; 39 (Suppl. 1): S13-S22

  43. Recommended screening test is fasting plasma glucose. • American Diabetes Association recommends screening for Type 2 DM in all asymptomatic individuals ≥ 45 yrs of age using fasting plasma glucose. Laboratory test for screening

  44. If fasting test is normal, screening test should be repeated every three years. • If fasting blood glucose level is normal but there is strong clinical suspicion then OGTT/HbA1C. Laboratory test for screening

  45. High risk individuals ---Obese Family h/o DM Hypertension Dyslipidemia Impaired glucose tolerance Selective screening Screening test is performed at earlier age ( 30 yrs ) and repeated more frequently

  46. Monitoring of Blood Glucose SMBG

  47. Self Monitoring of Blood Glucose- SMBG Regular use of SMBG devices by diabetic patients has improved the management of DM. SMBG devices measure capillary whole blood glucose obtained by finger prick and use test strips that incorporate glucose oxidase or hexokinase.

  48. Self Monitoring of Blood Glucose- SMBG SMBG devices yield unreliable results at very high and very low glucose levels. It is necessary to periodically check the performance of glucometer by measuring parallel venous plasma glucose in the laboratory.

  49. Above target glucose range People with diabetes should spent In a blood glucoserange of 70–180 mg/dL At least 17 hours a day, more than 70% of their time (3.9-10 mmol/L) Level 2 hyperglycemia Minimize (>13.1 mmol/L) (>13.1 mmol/L) Level 1 hyperglycemia (10-13.1 mmol/L) (10-13.1 mmol/L) >17 hours Time-In-Range ‘Time-In-Range’ & What’s Above/ Below From ‘In-Range’? (3.9-10 mmol/L) Target in glucose range Below target glucose range Level 1 hypoglycemia (3.1-3.9 mmol/L) <1 hour Level 2 hypoglycemia (<3.1 mmol/L) Battelino T, et al. Diabetes Care. 2019 Aug;42(8):1593-1603, Advani A. Diabetologia. 2020;63(2):242–252.

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