Clinical Biochemistry — MCQs

Clinical Biochemistry Indian Medical PG Practice Questions and MCQs

Question 301: A patient presents 12 hours following a myocardial infarction. Which of the following enzymes will be elevated at this period?

A. Lactate dehydrogenase
B. Creatine phosphokinase (Correct Answer)
C. Myoglobin
D. Serum glutamate oxaloacetate transferase (SGOT)

Explanation: ***Creatine phosphokinase*** - **Creatine phosphokinase (CK-MB)** levels begin to rise within **3-6 hours** after an MI, peak at **12-24 hours**, and return to baseline within **48-72 hours**. - At 12 hours post-MI, CK-MB would be significantly elevated and near its peak, making it the most reliable marker for diagnosis at this timepoint. *Lactate dehydrogenase* - **Lactate dehydrogenase (LDH)** levels rise much later, typically around **24-48 hours** after an MI, and peak at **3-6 days**. - At 12 hours post-MI, LDH elevation would be minimal or non-existent. *Myoglobin* - **Myoglobin** is one of the earliest markers to rise, appearing within **1-4 hours** post-MI and peaking around **6-7 hours**. - While elevated at 12 hours, it may already be declining, and it **lacks cardiac specificity** (also released from skeletal muscle injury), making it less reliable than CK-MB for MI diagnosis. *Serum glutamate oxaloacetate transferase (SGOT)* - **SGOT (AST)** levels start to rise around **6-12 hours** post-MI, peak at **18-36 hours**, and return to normal within **3-7 days**. - While it would be beginning to rise at 12 hours, **CK-MB** is more elevated and more specific for cardiac injury at this timepoint.

Question 302: Biochemical etiology of Alzheimer's disease relates to:

A. Dopamine
B. Acetylcholine (Correct Answer)
C. GABA
D. Serotonin

Explanation: ***Acetylcholine*** - Alzheimer's disease is significantly associated with a **reduction in cholinergic neuronal activity** in the brain, impacting memory and learning. - Medications for Alzheimer's disease often aim to **increase acetylcholine levels** or prevent its breakdown (e.g., cholinesterase inhibitors). *Dopamine* - **Dopamine deficits** are primarily associated with **Parkinson's disease**, affecting motor control and movement. - While dopamine may play a minor role, it is **not considered the primary biochemical etiology** of Alzheimer's. *GABA* - **GABA (gamma-aminobutyric acid)** is the main inhibitory neurotransmitter in the brain and is often associated with anxiety disorders and epilepsy. - While GABAergic system changes can occur in Alzheimer's, they are **secondary to the primary cholinergic dysfunction**. *Serotonin* - **Serotonin** is widely known for its role in mood, sleep, and appetite regulation, and its imbalances are linked to depression and anxiety. - While some **serotonergic changes** can be observed in Alzheimer's disease, the primary biochemical deficit is not serotonin.

Practice by Chapter

Liver Function Tests

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Kidney Function Tests

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Cardiac Markers and Enzymes

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Pancreatic Function Tests

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Glucose Tolerance Tests

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Lipid Profile and Cardiovascular Risk

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Tumor Markers

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Hormonal Assays and Interpretation

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Electrolytes and Acid-Base Balance Tests

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Cerebrospinal Fluid Analysis

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Point-of-Care Testing

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Quality Control in Clinical Biochemistry

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