Clinical Chemistry

• Carbohydrates are organic compounds composed of carbon, hydrogen, oxygen [Cx(H20)y], which, along with lipids and proteins, provide energy and contribute to the structure of organisms.
• Types of carbohydrates include Monosaccharides (Glucose, Frustose, Galactose), Disaccharides (Sucrose, Lactose, Maltose), and Polysaccharides (Glycogen, Starch, Cellulose, Chitin).
• Glucose is the only form of sugar that can be directly utilized by the body as energy.
• Disaccharides are formed by the combination of two monosaccharides.
• Polysaccharides are long chains of monosaccharides.
• Glycogen is the major storage form of glucose in man/animals.
• The pancreas is both an endocrine and exocrine gland (heterocrine).
• Beta cells in the pancreas secrete insulin, amylin, and C-peptide.
• C-peptide and insulin are secreted in equal amounts but the ratio in plasma is 5:1 - 15:1 due to increased hepatic clearance of insulin.
• C-peptide and insulin are from proinsulin.
• Alpha cells in the pancreas secrete glucagon.
• Delta cells in the pancreas secrete somatostatin.
• The exocrine part of the pancreas consists of duct cells that secrete bicarbonate and acinar cells that secrete digestive enzymes (amylase, lipase).
• Insulin, C-peptide, amylin, and glucagon are secreted by pancreatic islets.
• Enzymatic methods for glucose detection include glucose oxidase and hexokinase-G6PD.
• Copper reduction method is the oldest method for glucose detection, with the principle being that glucose and other reducing sugars convert cupric to cuprous ions in the presence of heat and alkali.
• Nelson Somogyi method is a chemical method for glucose detection, after PFF preparation, non-glucose reducing substances are adsorbed by barium sulfate.
• Clinitest method is an enzymatic method for glucose detection, which detects all reducing sugars and uses urine as a sample.
• Ferric reduction method, also known as Hagedorn Jensen method, is a chemical method for glucose detection, with the principle being that reduction of yellow ferricyanide to colorless ferrocyanide by reducing sugars is measured.
• Neocuproine method is a chemical method for glucose detection, where cuprous ions react with neocuproine to form a complex (yellow or yellow-orange).
• Folin Wu method is a chemical method for glucose detection, but it is not specific and non-glucose reducing substances also react with the test.
• Benedict’s method is a chemical method for glucose detection, used to detect and quantify reducing substances in body fluids, and uses citrate and tartrate as stabilizing agent.
• Ferric reduction (Hagedorn-Jensen) method is also a chemical method for glucose detection.
• Disappearance of color in ferric reduction method is measured at 400 nm and it is employed in autoanalyzers.
• Isotope dilution gas chromatography/mass spectrometry is a method for glucose detection.
• Benedict's method uses copper sulfate, sodium carbonate, sodium citrate, and sodium hydroxide as stabilizing agents, while Clinitest uses copper sulfate, sodium carbonate, sodium citrate, and sodium hydroxide.
• Chemical methods for glucose detection include copper reduction, Folin Wu method, Nelson Somogyi method, neocuproine method, Benedict’s method, and Clinitest method.
• Because β-hydroxybutyrate levels are high in diabetic ketoacidosis (DKA) and fall with treatment, whereas acetoacetic acid and acetone levels rise with treatment, urinary ketone strips are not useful for monitoring therapy.
• Calculation of the anion gap is employed instead to monitor recovery from DKA.
• Diagnosis of GDM can be done through a one-step approach (OGTT) for high-risk women or a two-step approach (initial screening test followed by OGTT) for women with average risk.
• Requirements for OGTT include the patient being ambulatory (mobile), the test being performed after an overnight 8 to14-hour fasting (not longer than 16 hours), an unrestricted diet of 150g carbohydrate/day for 3 days prior to testing, and not eating food, drinking tea, coffee, or alcohol, or smoking cigarettes during the test.
• One-Step Method for GDM diagnosis involves collecting fasting plasma (8-hour), giving 75 gram glucose, and then collecting plasma after 1 and 2 hours.
• Food (polysaccharides) are digested by the mouth, esophagus, stomach, small intestine, and blood.
• Two-Step Method for GDM diagnosis involves collecting fasting plasma (8 hour), giving 100 gram glucose, and then collecting plasma after 1, 2, and 3 hours.
• Glucose intolerance that develops during approximately 7% of all pregnancies should be screened for between 24-28 weeks of gestation.
• Gestational Diabetes Mellitus (GDM) is a condition where the body is unable to metabolize carbohydrates due to hormonal changes occurring in pregnancy and disappearing after delivery.
• Type II DM is characterized by the presence of proinsulin in the Beta cell, insulin in the pancreas, C-peptide in the blood, and is diagnosed late, often leading to cytotoxic T cells and Type IV hypersensitivity.
• GDM converts to DM within 10 years in 30-40% of cases.
• Specific types of diabetes include pancreatic disorders/pancreatectomy, endocrine disorders such as Cushing's syndrome, phaeochromocytoma, acromegaly, hyperthyroidism, drug or chemical inducers like dilantin and pentamidine, and genetic syndromes like Down syndrome, Klinefelter syndrome, Turner syndrome, etc.
• GSD Ia, also known as Von Gierke, is characterized by a deficiency of Glucose-6-Phosphatase.