Clinical Chemistry Conversion Factors

Laboratory Apparatus

• Sediments sink while supernatant floats in centrifugation.
• Swinging bucket rotor operates vertically at rest and horizontally in motion, providing more air resistance.
• Angle or fixed-head rotors (25º - 40º) minimize air resistance, allowing for quicker sedimentation.
• Calibration requires speed measurement tools such as tachometers or timers. Speed checks needed every 3 months.
• Automatic pipettes come in two types: air displacement (uses disposable tips) and positive-displacement (for high-density samples without an air cushion).

Exercise and Biochemical Changes

• Exercise increases levels of cortisol, glucagon, lactate dehydrogenase (LDH), creatine kinase (CK), creatinine, and aspartate aminotransferase (AST).
• Exercise decreases glucose, triglycerides, and cholesterol.
• Fist clenching raises potassium, phosphate, and lactate levels.

Gastrointestinal Physiology

• Salivary glands release amylase upon food ingestion, aiding in starch breakdown.
• Gastrin is secreted in the stomach, stimulating parietal cells for hydrochloric acid (HCl) production, leading to decreased chloride and increased bicarbonate.
• Blood glucose levels should be assessed alongside cerebrospinal fluid (CSF) glucose, which is about 40-60% of plasma glucose concentrations.

Meningitis and Microbial Infections

• Decreased CSF glucose levels are indicative of bacterial, tubercular, fungal, and amebic meningitis, with an exception for viral meningitis which thrives intracellularly.
• Bacterial meningitis is characterized by increased neutrophils and lactate alongside reduced glucose levels.

Inborn Errors of Metabolism

• Galactosemia: Requires diagnostic testing for erythrocyte galactose-1-phosphate uridyl transferase activity.
• Essential Fructosuria: Diagnosed by detecting fructose in urine post-fructokinase activity.

Chromatography Techniques

• Utilizes various media, such as paper or gel, for separating soluble components.
• Common applications include monoclonal gammopathy and drug testing, using materials like Whatman paper and HPLC (High-Performance Liquid Chromatography).
• Chromatography separates substances based on their movement through a stationary phase assisted by a mobile phase.

Specimen Collection and Handling

• Hemodilution and hemoconcentration are influenced by the patient's position (seated/supine vs. standing) at the time of blood collection.
• Certain specimens like lactic acid, ammonia, and blood gases must be protected from air exposure to prevent contamination.
• Ice slurry storage is crucial for slowing down mitochondrial metabolism in samples.

Analytical Methods in Clinical Chemistry

• Spectrophotometry: Measures the light absorbed and transmitted by a solution, following Beer’s Law for concentration analysis.
• Flame Emission Photometry: Analyzes the light emitted by atoms in a flame; suitable for unexcited elements while considering advantages and disadvantages like turbidity caused by lipids.
• Requires appropriate calibration and correction methods, including the use of serum with reagents to account for color interferences.

Diurnal Variations and Normal Ranges

• Key hormones and metabolites exhibit significant variations throughout the day, including cortisol, ACTH, and glucose.
• Normal reference intervals fluctuate based on fasting or non-fasting states, and the collection timing influences results.
• Chronic conditions such as liver disease markedly affect ammonia and urea levels.

This quiz covers the conversion factors between different units of measurement in clinical chemistry, including SI units, mg/dL, and more. Test your knowledge of clinical chemistry and laboratory medicine.