Diabetes & Laboratory Tests

MAC Academy DIABETES & LABORATORY TESTS 1. What is Diabetes Mellitus? Diabetes Mellitus (DM) is a chronic metabolic disorder characterized by an elevated level of glucose in the blood (Hyperglycemia). Glucose is the main source of energy for many cells in the body. To enter many cells and be used effectively, glucose depends mainly on a hormone called Insulin.  What is Insulin? o Insulin is a hormone produced by the β-cells of the pancreas. o Its main function is to help glucose move from the blood into cells and to maintain normal blood glucose levels.  What happens in Diabetes? Diabetes develops when: • • • The body does not produce enough insulin. The body cannot use insulin effectively (Insulin Resistance). Or both mechanisms occur together. As a result: ↓ Insulin action → ↓ Glucose uptake → ↑ Blood Glucose → Hyperglycemia Persistent hyperglycemia can damage blood vessels and different organs over time. 1 MAC Academy 2. Types of Diabetes  Type 1 Diabetes Mellitus o Type 1 diabetes occurs mainly because of autoimmune destruction of pancreatic β-cells. ▪ This leads to: o Severe insulin deficiency Therefore, patients with Type 1 diabetes require insulin therapy for survival. It commonly develops in children and young adults, but it can occur at any age.  Type 2 Diabetes Mellitus o Type 2 diabetes is the most common type of diabetes. o It is mainly associated with: ▪ Insulin Resistance + Progressive β-cell dysfunction ✓ Initially, the pancreas may produce insulin, but body tissues do not respond to it properly. ✓ Over time, insulin production may become insufficient. Risk factors include: • • • • • Obesity Physical inactivity Family history Increasing age Unhealthy lifestyle Gestational Diabetes Gestational diabetes is diabetes diagnosed during pregnancy. It occurs when the body's insulin requirements increase during pregnancy and insulin action becomes insufficient to maintain normal glucose levels. It usually improves after delivery, but women who develop gestational diabetes have an increased risk of developing Type 2 diabetes later in life. 2 MAC Academy 3. Laboratory Tests for Diabetes Laboratory testing is essential for: • • • • Diagnosis of diabetes Screening for diabetes Monitoring glucose control Detecting complications The main tests include: 1. Fasting Plasma Glucose — FPG Fasting plasma glucose measures blood glucose after fasting. The patient should have no caloric intake for at least 8 hours before the test. It reflects the glucose level at the time of testing. 2. Random Plasma Glucose — RPG Random plasma glucose can be measured at any time of the day, regardless of the time of the last meal. It is particularly useful when a patient has symptoms suggestive of hyperglycemia. A random plasma glucose level of: ≥200 mg/dL together with classic symptoms of hyperglycemia can support the diagnosis of diabetes. 3. Hour Postprandial Glucose — 2h-PPG Postprandial glucose is the blood glucose level measured after a meal. The 2-hour postprandial glucose is usually measured 2 hours after the beginning of a meal. It helps evaluate how the body handles glucose after food intake. It can be useful in: 3 MAC Academy • • • Monitoring diabetic patients Detecting post-meal hyperglycemia Assessing glucose control A commonly used target for many non-pregnant adults with diabetes is: <180 mg/dL at 1–2 hours after the beginning of a meal However, treatment targets may vary according to the patient's condition. 4. Oral Glucose Tolerance Test — OGTT OGTT evaluates the body's response to a standardized glucose load. After an appropriate fasting period, the patient consumes a glucose solution, and blood glucose is measured at specified times. The 2-hour value is commonly used for diagnosis. 2-hour OGTT: • • • Normal: <140 mg/dL Prediabetes: 140–199 mg/dL Diabetes: ≥200 mg/dL OGTT is also commonly used in the evaluation of gestational diabetes. 5. HbA1c HbA1c is glycated hemoglobin. It reflects the average blood glucose level over approximately the previous 2–3 months. It does not require fasting. HbA1c is useful for: • • Diagnosis of diabetes in appropriate settings Monitoring long-term glycemic control Diagnostic values: • Normal: <5.7% 4 MAC Academy • • Prediabetes: 5.7–6.4% Diabetes: ≥6.5% HbA1c may be affected by conditions that alter red blood cell survival or hemoglobin. Why does HbA1c reflect the previous months? Glucose in the blood can bind to hemoglobin inside red blood cells. Because red blood cells survive for approximately 120 days, HbA1c provides an estimate of long-term glucose exposure. 6. Fructosamine Fructosamine measures glycated serum proteins, mainly glycated albumin. Unlike HbA1c, which reflects approximately 2–3 months of glucose exposure, fructosamine reflects average glucose levels over approximately 2–3 weeks. It can be useful when: • • • A shorter-term assessment of glucose control is needed. HbA1c is unreliable because of conditions affecting red blood cells or hemoglobin. There has been a recent change in diabetes treatment and an earlier assessment is required. ✓ Important: o Fructosamine is affected by conditions that alter serum protein levels, especially albumin. 7. C-Peptide C-peptide is released when the pancreas produces endogenous insulin. When insulin is produced, proinsulin is split into: Insulin + C-Peptide Therefore, C-peptide can be used to assess endogenous insulin production. Why do we measure C-Peptide? It helps answer an important question: How much insulin is the patient's pancreas actually producing? 5 MAC Academy C-peptide may be useful in: • • • Differentiating between types of diabetes in selected cases Assessing residual pancreatic β-cell function Evaluating endogenous insulin production Important point: Injected insulin does not contain C-peptide. Therefore: C-Peptide → reflects endogenous insulin production 4. Laboratory Interpretation & Diabetes Monitoring How do we interpret glucose results? The diagnosis of diabetes should not usually depend on an isolated abnormal result in an asymptomatic patient. Results should be interpreted according to the appropriate diagnostic criteria and clinical context. Important Diagnostic Values Fasting Plasma Glucose: • • • Normal: <100 mg/dL Prediabetes: 100–125 mg/dL Diabetes: ≥126 mg/dL HbA1c: • • • Normal: <5.7% Prediabetes: 5.7–6.4% Diabetes: ≥6.5% 2-hour OGTT: • • • Normal: <140 mg/dL Prediabetes: 140–199 mg/dL Diabetes: ≥200 mg/dL 6 MAC Academy Random Plasma Glucose: A value of ≥200 mg/dL in a patient with classic symptoms of hyperglycemia can support the diagnosis of diabetes. Diagnostic criteria should always be interpreted according to current guidelines and the clinical situation. Prediabetes o Prediabetes means that blood glucose is higher than normal but does not yet meet the diagnostic criteria for diabetes. o It indicates an increased risk of developing Type 2 diabetes and cardiovascular disease. o Early lifestyle modification can help reduce the risk of progression. Monitoring Diabetes After diagnosis, laboratory tests are used to monitor glycemic control. The most important routine marker is: HbA1c because it reflects long-term glucose exposure. However, HbA1c should not be interpreted without considering the patient's clinical condition. Conditions affecting red blood cells or hemoglobin can affect HbA1c results. Mini Clinical Case A patient has: • • Fasting Plasma Glucose = 135 mg/dL HbA1c = 6.8% Interpretation: Both results are within the diabetic range. The results should be interpreted according to the patient's clinical condition and appropriate diagnostic confirmation when required. 7 MAC Academy Important Summary Diabetes Mellitus → Chronic Hyperglycemia Insulin → Produced by pancreatic β-cells Type 1 → Mainly insulin deficiency Type 2 → Insulin resistance + β-cell dysfunction FPG → Current fasting glucose RPG → Glucose at any time OGTT → Response to a glucose load HbA1c → Average glucose over approximately 2–3 months Remember: FPG = Fasting OGTT = Glucose challenge HbA1c = Long-term glucose control Diabetes = Persistent Hyperglycemia Prediabetes = Increased glucose, but below the diabetes diagnostic range Test FPG Random glucose 2h-PPG OGTT HbA1c Fructosamine C-Peptide What does it tell us? Time reflected Fasting blood glucose Blood glucose at any time Glucose after a meal Response to a glucose load Average glucose Average glucose Endogenous insulin production Current Current Post-meal Mainly 2-hour response ~2–3 months ~2–3 weeks β-cell function 8