Clinical Biochemistry Flashcards
What is clinical biochemistry, and why is it essential in modern healthcare?
Clinical biochemistry (also known as medical biochemistry or clinical chemistry) involves the qualitative and quantitative analysis of body fluids to aid in diagnosing, treating, and preventing diseases. It helps identify abnormal body fluid constituents to detect pathological conditions.
What are the different categories of biochemical markers, and how are they used in clinical practice?
- Diagnostic markers: Help diagnose diseases (e.g., cardiac markers in myocardial infarction).
- Therapeutic follow-up markers: Monitor treatment efficacy (e.g., blood glucose in diabetes).
- Prognostic markers: Predict disease progression (e.g., tumor markers in cancer).
- Risk markers: Indicate susceptibility to disease (e.g., LDL cholesterol in atherosclerosis).
- Nutritional markers: Assess nutritional status (e.g., Vitamin B12, folates).
- Exposure markers: Measure toxic exposure (e.g., cotinine for smoking, GGT for alcoholism).
A 55-year-old man presents with chest pain and suspected myocardial infarction. What biochemical markers would you check?
- Troponins (T & I): Gold standard for MI diagnosis.
- Creatine Kinase-MB (CK-MB): Elevated in myocardial injury.
- Myoglobin: Rises early but is non-specific.
- LDH (Lactate Dehydrogenase): Increases in late-stage MI.
A 65-year-old man with chronic kidney disease has elevated blood urea nitrogen (BUN) and creatinine. What do these markers indicate?
- BUN: High levels suggest impaired renal function or dehydration.
- Creatinine: More specific for kidney function; elevated levels indicate reduced GFR.
- Urea-to-Creatinine Ratio: Helps differentiate pre-renal from renal causes of dysfunction.
A 50-year-old patient with jaundice and right upper quadrant pain has elevated AST, ALT, ALP, and GGT. What is the likely diagnosis?
- AST & ALT: Elevated in hepatocellular damage (e.g., hepatitis, fatty liver disease).
- ALP: High in bile duct obstruction or bone disease.
- GGT: Elevated in cholestasis and alcohol-induced liver disease.
A patient with suspected meningitis undergoes a lumbar puncture. What key biochemical markers are assessed in cerebrospinal fluid (CSF)?
- Glucose: Low in bacterial meningitis, normal/high in viral meningitis.
- Protein: Elevated in infections and neurological diseases.
- WBC Count: High in bacterial meningitis (neutrophilic), moderate in viral meningitis (lymphocytic).
- Chloride: Decreased in tuberculous meningitis.
A diabetic patient presents with polyuria and glycosuria. What findings would you expect in a urine analysis?
- Glucose: Present in uncontrolled diabetes.
- Ketones: Found in diabetic ketoacidosis (DKA).
- Protein (Albuminuria): Indicates diabetic nephropathy.
- Specific Gravity: Low in diabetes insipidus; high in dehydration.
Why is it important to separate plasma from blood immediately after collection for glucose testing?
- Prevents glycolysis, which artificially lowers glucose levels.
- Blood should be collected in fluoride tubes (gray cap) to inhibit glycolysis.
What is the difference between sensitivity and specificity in laboratory tests?
- Sensitivity: Ability to detect true positives (low false negatives).
- Specificity: Ability to detect true negatives (low false positives).
- Example: A highly sensitive test (e.g., D-dimer) rules out disease, while a highly specific test (e.g., troponin) confirms it.
What are the advantages and disadvantages of POCT in clinical biochemistry?
- Advantages: Rapid results, convenience, useful in emergencies.
- Disadvantages: Requires proper calibration, quality control, potential for misinterpretation.
What are common electrolyte imbalances, and what are their clinical manifestations?
- Hyponatremia: Confusion, seizures, nausea.
- Hyperkalemia: Arrhythmias, muscle weakness.
- Hypocalcemia: Tetany, Chvostek’s sign.
A patient with suspected hypothyroidism presents with fatigue and weight gain. What lab tests would confirm the diagnosis?
- TSH: Elevated in primary hypothyroidism.
- Free T4: Decreased in hypothyroidism.
What are the key markers for monitoring diabetes control?
- Fasting glucose: ≥126 mg/dL suggests diabetes.
- HbA1c: Long-term control, target <7%.
- C-peptide: Assesses endogenous insulin production.
A patient has metabolic acidosis with a high anion gap. What conditions should be considered?
- Diabetic ketoacidosis (DKA).
- Lactic acidosis.
- Methanol or ethylene glycol poisoning.
What are the biochemical markers for liver function assessment?
- Bilirubin: Elevated in liver disease.
- Albumin: Low in chronic liver disease.
- PT/INR: Prolonged in liver dysfunction.
What are the roles of minerals in clinical biochemistry, and what are some examples?
Minerals, including macro and trace elements, are essential for energy production, osmotic pressure balance, acid-base regulation, neural function, and enzyme activation. Examples include:
* Phosphorus (P) – Bone health, energy metabolism
* Calcium (Ca) – Muscle contraction, blood clotting
* Sodium (Na) – Fluid balance, nerve signaling
* Potassium (K) – Cardiac and neuromuscular function
* Chloride (Cl) – Acid-base balance
* Zinc (Zn), Copper (Cu), Cobalt (Co), Iron (Fe) – Enzyme activation, immune function
What are the key components of a urine analysis, and what do they indicate?
- Physical Analysis: Color, odor, turbidity, volume
- Chemical Analysis: Glucose (diabetes), protein (kidney damage), ketones (DKA), bilirubin (liver disease), nitrites (UTI), blood (bleeding or infection)
- Microscopic Analysis: RBCs (hematuria), WBCs (infection), casts (kidney disease), crystals (renal stones)
What are the key biochemical markers assessed in cerebrospinal fluid (CSF), and what do they indicate?
- Glucose: Low in bacterial meningitis, normal/high in viral meningitis
- Protein: Elevated in infections, neurological diseases
- WBC Count: High in bacterial (neutrophilic) and viral (lymphocytic) meningitis
- Chloride: Decreased in tuberculous meningitis
What are the key aspects of quality control in clinical biochemistry?
- Quality Control (IQC): Daily checks for precision and accuracy
- External Quality Assessment (EQA): Inter-laboratory comparisons
- Validation of Methods: Sensitivity, specificity, reproducibility
- ISO Accreditation: Compliance with international standards (ISO 15189)
What are the advantages and disadvantages of point-of-care testing (POCT)?
Advantages: Rapid results, convenience, useful in emergencies (e.g., glucose monitoring, blood gases in ICU) Disadvantages: Expensive, requires proper calibration and maintenance, potential for misinterpretation
What are the key mechanisms that cause variations in biochemical markers?
- Metabolites: Changes due to synthesis abnormalities, transporter defects, metabolic blockages, or gene regulation issues.
- Proteins: Variations from overexpression, cell death, cellular damage, or extracellular protease activity.
Why is the pre-analytical phase critical in clinical biochemistry?
- Ensures correct sample collection, handling, and storage.
- Reduces errors caused by hemolysis, contamination, or incorrect timing.
- Prevents degradation of unstable analytes (e.g., glucose degradation without fluoride).
What are exposure markers, and how are they used in clinical biochemistry?
- Measure an individual’s exposure to toxic agents.
- Examples:
- Cotinine: Marker for smoking exposure.
- Gamma-glutamyl transferase (GGT): Alcohol consumption indicator.
- Heavy metals (Lead, Mercury, Arsenic): Environmental toxin exposure.
What are hazardous biological samples, and how should they be handled?
- Examples: HIV-positive blood, Hepatitis B samples.
- Precautions:
- Always assume samples are potentially infectious.
- Use proper labeling (yellow “Hazardous Sample” tags).
- Follow biosafety protocols for handling, transport, and disposal.
What other biological fluids are analyzed in clinical biochemistry, and what do they indicate?
- Pleural fluid: Assesses pleural effusions (infection, malignancy).
- Ascitic fluid: Detects peritonitis or liver cirrhosis.
- Synovial fluid: Diagnoses arthritis and joint infections.
- Saliva & Sweat: Used in drug testing, cystic fibrosis screening.
- Cerebrospinal fluid (CSF): Evaluates meningitis, encephalitis, and neurological diseases.
