Ace your Year 3 Chemical Pathology exams with this comprehensive practice test. Review key concepts, test your knowledge, and boost your confidence for success
MBPA 3600 - Year Three MBChB --- INSTRUCTIONS TO CANDIDATES - Section A : Short Answer Questions (10 marks each) - Answer ANY TWO questions - Section B : Long Essay Questions (20 marks each) - Answer ANY ONE question - Time Allowed : 2 hours - Total Marks : 40 marks --- SECTION A: SHORT ANSWER QUESTIONS (10 Marks Each) Answer ANY TWO Questions --- QUESTION 1 A 55-year-old diabetic patient presents to the emergency department with confusion, rapid breathing, and fruity breath odor. Random blood glucose is 28 mmol/L. (a) Define diabetic ketoacidosis (DKA). (2 marks) (b) List FIVE biochemical investigations you would request to confirm and manage DKA. (5 marks) (c) Explain the biochemical basis for the acid-base disturbance in DKA. (3 marks) ANSWER TO QUESTION 1 (a) Definition of Diabetic Ketoacidosis (2 marks) - DKA is a life-threatening acute metabolic complication of diabetes mellitus characterized by hyperglycemia (blood glucose 11 mmol/L), ketonemia/ketonuria, and metabolic acidosis (pH 4.5 mIU/L) - Low Free T4 ( 300 mg/g) - Serum creatinine and eGFR 2. Cardiovascular Disease: - Monitor: lipid profile (total cholesterol, LDL, HDL, triglycerides) - Cardiac biomarkers if symptomatic 3. Diabetic Neuropathy: - Clinical assessment primarily - May check vitamin B12 levels (metformin can cause deficiency) 4. Metabolic Monitoring: - Liver function tests (statins, fatty liver disease) - Electrolytes (diuretics, ACEI/ARBs) - Thyroid function (autoimmune association in Type 1) --- QUESTION 12 Discuss Renal Function Tests in detail: (a) Describe the biochemical assessment of glomerular function. (8 marks) (b) Explain the biochemical assessment of tubular function. (6 marks) (c) Discuss the role of urinalysis in evaluating renal disease. (6 marks) ANSWER TO QUESTION 12 (a) Biochemical Assessment of Glomerular Function (8 marks) 1. Serum Creatinine (2 marks): - Endogenous marker produced from muscle metabolism at constant rate - Filtered freely by glomerulus, not reabsorbed - Elevated in renal impairment (normal: 60-120 μmol/L) - Limitations: influenced by muscle mass, age, gender, diet - Not sensitive to early renal dysfunction (rises significantly only after 50% nephron loss) 2. Blood Urea Nitrogen (BUN) / Serum Urea (2 marks): - End product of protein metabolism - Filtered by glomerulus, partially reabsorbed in tubules - Normal: 2.5-7.5 mmol/L - Less specific than creatinine (affected by protein intake, hydration, GI bleeding, catabolic states) - BUN/Creatinine ratio useful: 20:1 suggests pre-renal azotemia 3. Estimated Glomerular Filtration Rate (eGFR) (2 marks): - Most important measure of kidney function - Calculated using equations: CKD-EPI, MDRD - Uses serum creatinine, age, sex, race - Normal: 90 mL/min/1.73m² - CKD staging based on eGFR:Stage 1: ≥90 (with kidney damage) - Stage 2: 60-89 - Stage 3: 30-59 - Stage 4: 15-29 - Stage 5: 1.020, osmolality 800 mOsm/kg) - Impaired in tubular dysfunction - Early marker of tubular disease 2. Urine Acidification Test (2 marks): - Assesses distal tubular function - Ammonium chloride loading test - Normal: urine pH should fall below 5.3 - Impaired in renal tubular acidosis (RTA) - Types of RTA: Type 1 (distal), Type 2 (proximal), Type 4 (hyperkalemic) 3. Tubular Markers (2 marks): Beta-2 Microglobulin: - Freely filtered, reabsorbed by proximal tubule - Elevated in urine indicates proximal tubular damage N-Acetyl-Beta-D-Glucosaminidase (NAG): - Enzyme from tubular cells - Elevated in urine indicates tubular injury Retinol Binding Protein: - Low molecular weight protein - Increased urinary excretion in tubular dysfunction Amino acids and glucose in urine: - Abnormal presence indicates proximal tubular defects (Fanconi syndrome) (c) Role of Urinalysis in Evaluating Renal Disease (6 marks) 1. Physical Examination (2 marks): Color and Appearance: - Normal: pale to dark yellow, clear - Red/brown: hematuria, hemoglobinuria, myoglobinuria - Cloudy: pyuria, infection, crystals Specific Gravity: - Normal: 1.003-1.030 - Fixed at 1.010: isosthenuria (tubular dysfunction) - Low: diabetes insipidus, overhydration - High: dehydration, SIADH Volume: - Normal: 800-2000 mL/24hr - Oliguria ( 3000 mL/day): diabetes mellitus, diabetes insipidus 2. Chemical Examination (Dipstick) (2 marks): Protein: - Normal: 10⁵ CFU/mL significant) --- QUESTION 13 Write detailed notes on Liver Function Tests: (a) Describe the biochemical tests used to assess hepatocellular function. (8 marks) (b) Explain the biochemical tests used to assess cholestasis and biliary obstruction. (6 marks) (c) Discuss the pattern of liver function test abnormalities in different types of liver disease. (6 marks) ANSWER TO QUESTION 13 (a) Biochemical Tests for Hepatocellular Function (8 marks) 1. Aminotransferases (Transaminases) (2 marks): Alanine Aminotransferase (ALT): - More specific for liver (found mainly in hepatocytes) - Normal: 7-56 U/L - Elevated in hepatocellular injury Aspartate Aminotransferase (AST): - Found in liver, heart, muscle, kidney - Normal: 10-40 U/L - Less specific than ALT Clinical Significance: - AST/ALT ratio 2: alcoholic liver disease - Very high levels ( 1000 U/L): acute viral hepatitis, drug-induced hepatitis, ischemic hepatitis 2. Synthetic Function Tests (3 marks): Serum Albumin: - Synthesized exclusively by liver - Normal: 35-50 g/L - Half-life: 20 days - Low in chronic liver disease, malnutrition, nephrotic syndrome - Indicates hepatic synthetic capacity Prothrombin Time (PT) / INR: - Measures clotting factors (II, VII, IX, X) synthesized by liver - Prolonged in liver disease (reduced synthesis) or vitamin K deficiency - INR 1.5 indicates significant hepatic dysfunction - Useful in acute liver failure assessment Total Protein: - Normal: 60-80 g/L - Decreased in chronic liver disease - Includes albumin and globulins 3. Serum Bilirubin (2 marks): Total Bilirubin: - Normal: 3-17 μmol/L - Elevated in hepatocellular disease, cholestasis, hemolysis Direct (Conjugated) Bilirubin: - Normal: 500 U/L, often 1000 U/L) - ALT AST - Mild to moderate elevation of bilirubin (conjugated unconjugated) - Slight elevation of ALP ( ALT (AST/ALT ratio 2) - Moderate elevation of transaminases ( 3-10 times normal) - Marked elevation of GGT - Elevated conjugated bilirubin - Mild elevation of transaminases ( 25 pmol/L) - Elevated Free T3 ( 6.5 pmol/L) - T3 may be disproportionately elevated (T3 toxicosis) - In subclinical hyperthyroidism: low TSH with normal T4 and T3 (c) Differentiation between Graves' disease and toxic multinodular goiter (3 marks) Graves' Disease: - Positive TSH receptor antibodies (TRAb positive) - Diffusely enlarged thyroid gland - Associated with ophthalmopathy (exophthalmos) and dermopathy - More common in younger patients - Autoimmune etiology Toxic Multinodular Goiter: - Negative TSH receptor antibodies - Nodular thyroid enlargement on palpation/scan - No ophthalmopathy - More common in older patients ( 50 years) - Radioiodine uptake shows patchy/heterogeneous uptake --- QUESTION 15 Discuss the principles of clinical toxicology and therapeutic drug monitoring. (a) Explain THREE pre-analytical factors affecting specimen collection in toxicology. (6 marks) (b) Describe the role of therapeutic drug monitoring (TDM) in patient management. (4 marks) ANSWER TO QUESTION 15 (a) Three pre-analytical factors in toxicology specimen collection (6 marks - 2 marks each) 1. Timing of Specimen Collection: - Critical for accurate interpretation of drug/toxin levels - Should be collected at specific times relative to drug administration (peak and trough levels) - For suspected poisoning, collect as soon as possible after exposure - Serial samples may be needed to assess elimination kinetics - Consider drug half-life when timing collections 2. Type of Specimen: - Blood (serum/plasma) most common for quantitative analysis - Whole blood required for some drugs (e.g., ciclosporin, tacrolimus) - Urine useful for screening and detecting drug metabolites - Gastri