Chemical Pathology MCQs

Question 1

Which of the following is NOT measured in a basic metabolic panel (BMP)?

Accepted Answer

Bilirubin — A BMP typically includes glucose, electrolytes (Na+, K+, Cl-, CO2), BUN, and creatinine. Bilirubin is part of liver function tests, not the BMP. ---

Question 2

Which test is the most specific for liver function?

Accepted Answer

ALT — ALT (Alanine aminotransferase) is more specific for hepatocellular injury as it's primarily found in the liver, while AST is found in multiple organs including heart and muscle. ---

Question 3

Which electrolyte is the most abundant cation in extracellular fluid?

Accepted Answer

Sodium — Sodium (Na+) is the predominant cation in extracellular fluid (normal: 135-145 mEq/L), while potassium is the main intracellular cation. ---

Question 4

An increased anion gap metabolic acidosis can be caused by

Accepted Answer

Lactic acidosis — Lactic acidosis causes increased anion gap metabolic acidosis due to organic acid accumulation. Diarrhea and RTA typically cause normal anion gap acidosis. ---

Question 5

Which analyte is most useful in the diagnosis of multiple myeloma?

Accepted Answer

Serum protein electrophoresis — SPEP detects monoclonal proteins (M-proteins) characteristic of multiple myeloma, showing abnormal immunoglobulin bands. ## Section 2: Endocrine Disorders & Hormone Assays ---

Question 6

Which of the following is an adrenal hormone?

Accepted Answer

Prolactin — Cortisol is produced by the adrenal cortex. T3 is thyroid hormone, prolactin is pituitary hormone, and ADH is produced by the hypothalamus. ---

Question 7

In primary hypothyroidism, TSH levels are typically

Accepted Answer

High — Primary hypothyroidism involves thyroid gland failure, so TSH is elevated due to loss of negative feedback from low thyroid hormones. ---

Question 8

Which hormone is most useful for diagnosing acromegaly?

Accepted Answer

IGF-1 — IGF-1 is more stable than GH and better reflects long-term GH secretion, making it the preferred screening test for acromegaly. ---

Question 9

Which test is used to confirm Cushing's syndrome?

Accepted Answer

Low-dose dexamethasone suppression test — This test differentiates normal individuals (who suppress cortisol) from those with Cushing's syndrome (who fail to suppress). ---

Question 10

Which enzyme deficiency is most common in congenital adrenal hyperplasia?

Accepted Answer

21-hydroxylase — 21-hydroxylase deficiency accounts for ~95% of CAH cases, leading to cortisol deficiency and androgen excess. ## Section 3: Kidney Function & Electrolytes ---

Question 11

The best marker for glomerular filtration rate (GFR) is

Accepted Answer

Serum cystatin C Correct — Cystatin C is less affected by muscle mass, age, and diet compared to creatinine, providing a more accurate GFR assessment. ---

Question 12

A low fractional excretion of sodium (FENa) suggests

Accepted Answer

Prerenal azotemia — FENa <1% indicates intact tubular function with appropriate sodium retention, typical of prerenal causes of AKI. ---

Question 13

Which electrolyte abnormality is associated with ECG changes such as peaked T waves?

Accepted Answer

Hyperkalemia — Hyperkalemia causes characteristic ECG changes: peaked T waves, widened QRS, and can progress to sine waves and cardiac arrest. ---

Question 14

Which acid-base disorder is commonly seen in patients with chronic kidney disease?

Accepted Answer

Metabolic acidosis — CKD causes metabolic acidosis due to decreased acid excretion, reduced ammonia production, and bicarbonate loss. ---

Question 15

Which of the following conditions leads to an increased BUN-to-creatinine ratio?

Accepted Answer

Prerenal azotemia — Prerenal azotemia increases BUN more than creatinine due to enhanced urea reabsorption, raising the BUN:Cr ratio 20:1. ## Section 4: Liver Function & Lipid Metabolism ---

Question 16

Which liver enzyme is most specific for hepatocellular injury?

Accepted Answer

ALT — ALT is predominantly found in hepatocytes, making it more specific for liver injury than AST, which is also found in cardiac and skeletal muscle. ---

Question 17

Which of the following is the best marker of cholestasis?

Accepted Answer

ALP — Alkaline phosphatase is elevated in cholestatic conditions due to increased synthesis and release from bile duct epithelium. ---

Question 18

Which lipoprotein is primarily responsible for transporting cholesterol to tissues?

Accepted Answer

LDL — LDL carries cholesterol from liver to peripheral tissues and is the major atherogenic lipoprotein. ---

Question 19

Familial hypercholesterolemia is caused by a defect in which receptor?

Accepted Answer

LDL receptor — FH is caused by mutations in the LDL receptor gene, leading to impaired cholesterol uptake and very high LDL levels. ---

Question 20

A fasting glucose level of 8.0 mmol/L (144 mg/dL) suggests

Accepted Answer

Diabetes mellitus — Fasting glucose ≥7.0 mmol/L (126 mg/dL) indicates diabetes mellitus. 144 mg/dL clearly meets this criterion. ## Section 5: Tumor Markers & Cancer Screening ---

Question 21

Which tumor marker is most commonly used for ovarian cancer screening?

Accepted Answer

CA 125 — CA 125 is the most widely used tumor marker for ovarian cancer, though it's not specific and can be elevated in benign conditions. ---

Question 22

A patient with suspected pancreatic cancer is likely to have elevated levels of

Accepted Answer

CA 19-9 — CA 19-9 is the most useful tumor marker for pancreatic adenocarcinoma, though it's also elevated in biliary obstruction. ---

Question 23

Which tumor marker is most specific for hepatocellular carcinoma?

Accepted Answer

AFP — Alpha-fetoprotein (AFP) is the most specific tumor marker for hepatocellular carcinoma, though it can also be elevated in other liver diseases. ---

Question 24

A patient with an enlarged prostate and elevated PSA should undergo

Accepted Answer

Prostate biopsy — Elevated PSA with enlarged prostate requires tissue diagnosis via biopsy to rule out prostate cancer. ---

Question 25

The presence of high levels of CEA is most suggestive of

Accepted Answer

Colorectal cancer — CEA (carcinoembryonic antigen) is most commonly associated with colorectal cancer, though it's not specific. ## Section 6: Acid-Base Disorders & Blood Gases ---

Question 26

Which of the following is a primary metabolic alkalosis?

Accepted Answer

Vomiting — Vomiting causes loss of gastric acid (HCl), leading to metabolic alkalosis. COPD causes respiratory acidosis. ---

Question 27

A patient with a pH of 7.25, PaCO₂ of 60 mmHg, and HCO₃⁻ of 24 mEq/L has

Accepted Answer

Respiratory acidosis — pH <7.35 with elevated PaCO₂ ( 45 mmHg) indicates respiratory acidosis. Normal bicarbonate suggests acute condition. ---

Question 28

Which of the following causes a normal anion gap metabolic acidosis?

Accepted Answer

Renal tubular acidosis — RTA causes normal anion gap acidosis due to impaired renal acid excretion. Other options cause high anion gap acidosis. ---

Question 29

A patient with metabolic acidosis and an increased anion gap likely has

Accepted Answer

Diabetic ketoacidosis — DKA produces ketoacids, causing high anion gap metabolic acidosis. RTA causes normal anion gap acidosis. ---

Question 30

Which compensatory response occurs in metabolic acidosis?

Accepted Answer

Increased respiratory rate — Metabolic acidosis triggers hyperventilation to blow off CO₂ and partially compensate for the acidosis. ## Case-Based MCQs Section 1: Electrolytes & Acid-Base Disorders ---

Question 31

A 65-year-old man with chronic kidney disease presents with weakness and palpitations. ECG shows peaked T waves. Lab results: K⁺ 6.5 mmol/L, Na⁺ 140 mmol/L, BUN 55 mg/dL, Creatinine 4.2 mg/dL. What is the next best step?

Accepted Answer

IV calcium gluconate — Severe hyperkalemia with ECG changes (peaked T waves) is a cardiac emergency. IV calcium stabilizes cardiac membrane first. ---

Question 32

A 50-year-old woman with severe vomiting for three days presents with muscle cramps and weakness. Lab results: Na⁺ 138 mmol/L, K⁺ 2.8 mmol/L, Cl⁻ 85 mmol/L, HCO₃⁻ 34 mmol/L. What is the acid-base disorder?

Accepted Answer

Metabolic alkalosis — High bicarbonate (34 mmol/L) with hypokalemia and hypochloremia from vomiting indicates metabolic alkalosis. ---

Question 33

A 35-year-old diabetic man presents with confusion and deep rapid breathing. Blood gas: pH 7.1, PaCO₂ 22 mmHg, HCO₃⁻ 10 mmol/L, glucose 550 mg/dL. What is the primary acid-base disorder?

Accepted Answer

Metabolic acidosis — Low pH (7.1) with low bicarbonate (10) and compensatory hyperventilation (low CO₂) indicates metabolic acidosis from DKA. ---

Question 34

A 72-year-old man with COPD presents with confusion. Blood gas: pH 7.28, PaCO₂ 60 mmHg, HCO₃⁻ 28 mmol/L. What is the most likely acid-base disorder?

Accepted Answer

Respiratory acidosis — Low pH with high CO₂ indicates respiratory acidosis. Elevated bicarbonate suggests chronic compensation. ---

Question 35

A 45-year-old woman with chronic diarrhea presents with weakness. Labs: Na⁺ 138 mmol/L, K⁺ 3.0 mmol/L, Cl⁻ 105 mmol/L, HCO₃⁻ 15 mmol/L. What is the likely diagnosis?

Accepted Answer

Normal anion gap metabolic acidosis — Anion gap = 138 - (105 + 15) = 18 (normal range). Diarrhea causes bicarbonate loss leading to normal anion gap acidosis. ## Case-Based MCQs Section 2: Kidney Function & Renal Pathology ---

Question 36

A 55-year-old hypertensive patient presents with swelling and decreased urine output. Labs: BUN 45 mg/dL, Creatinine 3.8 mg/dL, Na⁺ 134 mmol/L, K⁺ 5.2 mmol/L. Urine Na⁺ 500 mOsm/kg. What is the likely cause?

Accepted Answer

Prerenal azotemia — Low urine sodium (<20) and high urine osmolality ( 500) indicate intact tubular function trying to conserve sodium and water. ---

Question 37

A 70-year-old diabetic patient presents with chronic kidney disease. Labs: BUN 55 mg/dL, Creatinine 5.5 mg/dL, eGFR 15 mL/min. What stage of CKD is this?

Accepted Answer

Stage 5 Correct — eGFR <15 mL/min indicates Stage 5 CKD (kidney failure), requiring renal replacement therapy consideration. ---

Question 38

A patient with nephrotic syndrome has edema and proteinuria 3.5 g/day. What is the most likely biochemical abnormality?

Accepted Answer

Hypoalbuminemia — Massive proteinuria in nephrotic syndrome leads to hypoalbuminemia, causing decreased oncotic pressure and edema. ---

Question 39

A patient with acute tubular necrosis (ATN) will have

Accepted Answer

Muddy brown casts — Muddy brown casts are pathognomonic for ATN, indicating tubular epithelial cell sloughing. ---

Question 40

A patient with SIADH will most likely have which lab finding?

Accepted Answer

Hyponatremia — SIADH causes excessive water retention, leading to dilutional hyponatremia with concentrated urine. ## Case-Based MCQs Section 3: Endocrine Disorders ---

Question 41

A 60-year-old man presents with weight gain, moon facies, and hypertension. Labs: Cortisol remains high after low-dose dexamethasone suppression test. What is the likely diagnosis?

Accepted Answer

Cushing's syndrome — Failure to suppress cortisol with low-dose dexamethasone confirms Cushing's syndrome. Clinical features support this diagnosis. ---

Question 42

A 25-year-old woman presents with palpitations, weight loss, and sweating. Labs: TSH <0.1 mIU/L, Free T4 high. What is the most likely diagnosis?

Accepted Answer

Hyperthyroidism — Suppressed TSH with elevated T4 and classic hyperthyroid symptoms confirms hyperthyroidism. ---

Question 43

A 30-year-old woman presents with fatigue, hypotension, and hyperpigmentation. Labs: Na⁺ 129 mmol/L, K⁺ 5.8 mmol/L, Cortisol low. What is the likely diagnosis?

Accepted Answer

Addison's disease — Low cortisol with hyponatremia, hyperkalemia, and hyperpigmentation are classic for primary adrenal insufficiency (Addison's disease). ---

Question 44

A patient with secondary hyperparathyroidism due to chronic kidney disease will have

Accepted Answer

High PTH — CKD causes phosphate retention and vitamin D deficiency, leading to low/normal calcium and compensatory PTH elevation. ---

Question 45

Which of the following conditions is most commonly associated with hypercalcemia?

Accepted Answer

Hyperparathyroidism — Primary hyperparathyroidism is the most common cause of hypercalcemia in outpatients, followed by malignancy in hospitalized patients. ## Case-Based MCQs Section 4: Diabetes & Glucose Disorders ---

Question 46

A 40-year-old man with polyuria and polydipsia has fasting glucose of 150 mg/dL and HbA1c of 8.5%. What is the diagnosis?

Accepted Answer

Diabetes mellitus — Fasting glucose ≥126 mg/dL and HbA1c ≥6.5% both meet criteria for diabetes mellitus diagnosis. ---

Question 47

A patient presents with altered mental status and blood glucose of 35 mg/dL. What is the most likely cause?

Accepted Answer

Insulinoma — Severe hypoglycemia (35 mg/dL) with altered mental status suggests insulin excess, most likely from an insulinoma. ---

Question 48

A 65-year-old diabetic patient with non-healing ulcers likely has

Accepted Answer

Hyperglycemia-induced vascular damage — Chronic hyperglycemia causes microvascular and macrovascular complications, leading to poor wound healing. ---

Question 49

Which test is most useful for long-term diabetes monitoring?

Accepted Answer

HbA1c — HbA1c reflects average glucose over 2-3 months, making it ideal for long-term diabetes monitoring and management. ---

Question 50

A diabetic patient with nausea, abdominal pain, and high blood glucose should be evaluated for

Accepted Answer

Diabetic ketoacidosis — Nausea, abdominal pain with hyperglycemia in a diabetic patient suggests DKA, especially with ketosis and acidosis. ## Chemical Pathology Calculations Section ---

Chemical Pathology MCQs

Questions, Answers & Explanations