Untitled Quiz

Glucose Homeostasis Derangement - III

• Students should be able to define and explain impaired glucose tolerance, impaired fasting glucose, diabetes, and diabetic ketoacidosis after the lecture and practical demonstrations.
• Students should be able to describe the laboratory diagnosis of these conditions.
• Students should be able to describe the oral glucose tolerance test (OGTT).
• Students should be able to describe the significance of glycated Hb in blood and microalbumin in urine analysis.

Outline

• Tests for diagnosing diabetes mellitus (DM)
• Tests for monitoring DM control
• Tests for detecting DM complications

Diagnosis of Diabetes Mellitus

• Diagnosis is based on clinical features of long-standing or acute hyperglycemia.
• Evidence of hyperglycemia through laboratory testing (or a directly related effect of it).
• Clinical features + one abnormal lab result, or abnormal lab results at two separate occasions.

Normal Blood Glucose Curve

• Presents a graph of normal blood glucose levels over time after glucose ingestion.

Random Blood Glucose Level (RBS)

• Venous blood glucose is measured without considering the last meal.
• Normal: < 100 mg/dL or ≤ 5.6 mmol/L
• Diabetes: ≥ 200 mg/dL or ≥ 11.1 mmol/L

Fasting Blood Glucose Level (FBS)

• Venous blood glucose is measured at a fixed time after the last meal (no caloric intake for 8 hours).
• Normal: < 100 mg/dL or ≤ 5.6 mmol/L
• Diabetes: ≥ 126 mg/dL or ≥ 7.0 mmol/L

Post-prandial Blood Glucose Level (PPBS)

• Venous blood glucose is measured at a fixed time after a meal (usually 2 hours).
• Normal: < 140 mg/dL or < 7.8 mmol/L
• Diabetes: ≥ 200 mg/dL or ≥ 11.1 mmol/L

Oral Glucose Tolerance Test (OGTT)

• Venous blood glucose is measured at a fixed time after a fixed glucose load (1 hour and 2 hours).
• Normal OGTT 2hr: < 140 mg/dL or < 7.8 mmol/L
• Diabetes OGTT 2hr: ≥ 200 mg/dL or ≥ 11.1 mmol/L
• OGTT involves fasting for 8–12 hours, collecting a fasting blood glucose sample, ingesting 75g of glucose, and measuring blood glucose at fixed times, mostly at 2 hours.

HbA1c Test (Glycated Hb Levels)

• Glycation is the non-enzymatic binding of glucose to other substrates, directly proportional to glucose concentration in the blood.
• HbA1c, about 80% of glycated Hb, is used as an indirect measure of blood glucose levels.
• Normal: < 5.7%
• Diabetes: ≥ 6.5%
• Advantages of HbA1c: no need for fasting or timed samples, measures average blood glucose over 2-3 months, used to monitor control.
• Disadvantages of HbA1c: standardized only for adults, not reliable in increased red cell turnover or hemoglobinopathies, or pregnancy.

Fructosamine Test

• Measures glycated proteins/albumin levels in serum.
• Indicates average glucose levels over 2–3 weeks.
• Can be used when HbA1c isn't reliable, but depends on serum albumin levels.

Blood Sugar Series

• Often done during pregnancy to determine sugar control.
• Tests before and after breakfast, lunch, and dinner.

Detection of DM Complications

• Diabetic Nephropathy: Albumin loss in urine is a feature. <30mg/day is normal. Early kidney damage causes gradual increase above 30mg/day called Microalbuminuria, (30-300mg/day)
• Microalbuminuria can be tested in different urine samples (24-hour, less than 24-hour, or spot sample).
• Ketoacidosis (DKA):
• Arterial blood gas testing for pH, pCO2, HCO3 and base excess.
• Urine testing for ketone bodies.
• Plasma osmolality.

Prediabetes

• A category for those whose blood sugar or HbA1c test results are neither diabetic nor normal.
• Not a disease, but a high-risk group for developing DM.
• Impaired Fasting Glucose (IFG): FBS 100–125 mg/dL or 5.6–6.9 mmol/L
• Impaired Glucose Tolerance (IGT): OGTT 140–199 mg/dL or 7.8–11.0 mmol/L

WHO Criteria for Diagnosis of DM

• A summary table of normal, prediabetes, and diabetes values for RBS, FBS, OGTT, and HbA1c.

Urine Testing for Glucose

• Glucose appears in urine when blood glucose levels exceed the renal threshold.
• Not a diagnostic test, but used as a screening test.
• Benedict test is used to test for reducing substances, one of which is glucose.

OGTT in Pregnancy

• 75g OGTT, venous blood tested before, 1-hour, and 2-hour after.
• GDM (gestational diabetes mellitus) is diagnosed with any of fasting ≥92 mg/dL (5.1 mmol/L), 1-hour ≥ 180 mg/dL (10.0 mmol/L), or 2-hour ≥ 153 mg/dL (8.5 mmol/L).

C-peptide Levels

• A by-product of insulin synthesis, used to measure insulin production (beta cell function).
• Can be tested in a fasting state or after a standard meal

Antibody Testing

• Specific antibodies, like islet-cell antibodies (IA2), antibodies against glutamic acid decarboxylase (Anti-GAD65), and anti-insulin antibodies, can be detected in Type 1 DM, especially during early stages.

Monitoring Control of DM

• HbA1c is best for monitoring blood glucose control in DM patients.
• Other tests for blood glucose control include RBS, FBS, and OGTT