Clinical Biochemistry Practice Questions

Q: Which of the following is a synthetic oxygen carrier?

Perfluorocarbon. **Perfluorocarbon** - **Perfluorocarbons** (PFCs) are synthetic organic compounds that are chemically inert and can dissolve large amounts of gases, including oxygen. - Due to their ability to carry oxygen, PFCs have been investigated as **blood substitutes** and in drug delivery systems. *2,4-dinitrophenol* - **2,4-dinitrophenol** (DNP) is an **uncoupler of oxidative phosphorylation**, meaning it prevents ATP synthesis while electron transport continues, generating heat instead. - It is a metabolic poison and has been used as a weight-loss drug but is not an oxygen carrier. *Chlorofluorocarbon* - **Chlorofluorocarbons** (CFCs) are organic compounds containing carbon, chlorine, and fluorine, primarily known for their role as **refrigerants** and in **aerosol propellants**. - CFCs are environmentally harmful due to their impact on the ozone layer and do not function as oxygen carriers. *1-fluoro-2,4-dinitrophenol* - **1-fluoro-2,4-dinitrophenol** is a derivative of dinitrophenol and would likely share similar properties as an **uncoupler of oxidative phosphorylation**. - It is not recognized for its ability to carry oxygen.

Q: Cataract in cases of diabetes mellitus is due to accumulation of ?

Glycated crystallins. ***Glycated crystallins*** - In diabetes, high glucose levels lead to **non-enzymatic glycation** of lens proteins, primarily **crystallins**. - Glycation causes aggregation and insolubilization of crystallins, leading to increased **light scattering** and cataract formation. - Additionally, the **polyol pathway** (glucose → sorbitol via aldose reductase) causes sorbitol accumulation in the lens, contributing to osmotic stress and protein damage. - Both glycation and sorbitol accumulation are key mechanisms in diabetic cataractogenesis. *Calcified crystallins* - While calcification can occur in some forms of cataracts (e.g., age-related, traumatic), it is **not the primary mechanism** for diabetic cataracts. - Diabetic cataracts are predominantly linked to **metabolic changes** (hyperglycemia-induced glycation and polyol pathway) rather than mineral deposition. *Glycated fibrillins* - **Fibrillin** is an extracellular matrix glycoprotein important for elastic fibers in connective tissues, but it is **not a major structural protein of the lens**. - The lens is composed primarily of **crystallins** (α, β, γ), not fibrillins. - Therefore, fibrillin glycation would not directly cause lens opacification. *Calcified fibrillins* - This option incorrectly identifies both the protein type and the mechanism. - **Fibrillin calcification** is not a known pathway for diabetic cataractogenesis. - Diabetic cataracts result from crystallin modifications, not fibrillin changes.

Q: Bilirubin in serum can be measured by

Van den Bergh reaction. ***Van den Bergh reaction*** - The **Van den Bergh reaction** is a common laboratory method used to quantify **bilirubin** in serum. - This method differentiates between direct (conjugated) and indirect (unconjugated) bilirubin using a **diazotized sulfanilic acid** reagent. *Ehrlich's Reaction* - **Ehrlich's reaction** is primarily used to detect **urobilinogen** in urine, not bilirubin in serum. - It involves the reaction of urobilinogen with **Ehrlich's reagent** (p-dimethylaminobenzaldehyde) to form a red color. *Schlesinger's Reaction* - **Schlesinger's reaction** is a test for the presence of **urobilin** in urine. - It uses a zinc salt, which reacts with urobilin to produce a characteristic **green fluorescence**. *Fouchet's Reaction* - **Fouchet's reagent** is used in urine analysis to detect the presence of **bilirubin** in a semi-quantitative manner, often indicating liver disease or biliary obstruction. - This reaction typically employs trichloroacetic acid and ferric chloride to produce a characteristic color change.

Q: In which condition is 5-Hydroxyindoleacetic acid (HIAA) elevated in urine?

Carcinoid. ***Carcinoid*** - **Carcinoid tumors** can synthesize and release large amounts of **serotonin**, which is metabolized in the body to **5-HIAA**. - Elevated **urinary 5-HIAA** is a key diagnostic marker for **carcinoid syndrome**, indicating excessive serotonin production. *Alkaptonuria* - This is a rare genetic disorder characterized by the accumulation of **homogentisic acid** in the body, leading to dark urine upon standing and ultimately **ochronosis**. - It does not involve abnormalities in serotonin metabolism or 5-HIAA levels. *Albinism* - Albinism is a group of inherited disorders characterized by very **little or no melanin pigment production**, commonly affecting the skin, hair, and eyes. - This condition is related to **tyrosine metabolism** and has no direct link to 5-HIAA levels. *Phenylketonuria* - **PKU** is a metabolic disorder caused by a deficiency in the enzyme **phenylalanine hydroxylase**, leading to a buildup of **phenylalanine** in the body. - This condition primarily affects phenylalanine metabolism and has no direct relationship with 5-HIAA levels, which are associated with serotonin metabolism.

Q: Which of the following is a positive acute phase protein that enhances the acute phase response?

Fibrinogen. ***Fibrinogen*** - **Fibrinogen** is a key **positive acute phase protein** whose concentration increases significantly during inflammation - Its elevation contributes to the acute phase response by promoting **blood clotting** and influencing **erythrocyte sedimentation rate (ESR)** - Along with C-reactive protein (CRP), haptoglobin, and serum amyloid A, fibrinogen is among the major positive acute phase reactants *Transferrin* - **Transferrin** is a **negative acute phase protein**, meaning its concentration decreases during inflammation - This reduction is part of the body's iron-sequestration strategy to limit iron availability for invading pathogens - The decrease in transferrin helps restrict bacterial growth by reducing available iron *Albumin* - **Albumin** is a prominent **negative acute phase protein**, with its concentration decreasing during acute inflammation due to redistribution and reduced synthesis - It plays a vital role in maintaining **oncotic pressure** and transporting various substances - Its decline reflects the severity of inflammation and is used as a marker of the acute phase response *Prealbumin* - **Prealbumin** (also known as transthyretin) is a **negative acute phase protein** and a sensitive marker of nutritional status - Its rapid decline during inflammation makes it a useful indicator, as its synthesis is quickly reduced - It has a short half-life (2-3 days), making it more sensitive to acute changes than albumin

Q: Converging point of both pathways in coagulation is at:

Stuart factor X. ***Stuart factor X*** [1][2] - It is the main **converging point** of the coagulation cascade, where both the intrinsic and extrinsic pathways meet to initiate the common pathway [1]. - Activated factor X leads to the conversion of **prothrombin to thrombin**, pivotal for clot formation [2]. *Factor VII* [2] - Primarily involved in the **extrinsic pathway** of coagulation, activating factor X, but does not serve as a converging point. - Its function is limited to starting the coagulation cascade, particularly upon tissue injury. *Factor IX* [2] - A key component of the **intrinsic pathway**, it leads to the activation of factor X but is not the point where both pathways converge. - It requires **factor VIII** for its activation, further illustrating its role within a specific pathway. *Factor VIII* - Also part of the **intrinsic pathway**, it acts as a cofactor for factor IX but does not integrate both pathways into a common point. - Its deficiency is associated with **Hemophilia A**, underscoring its specific pathway involvement. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Hemodynamic Disorders, Thromboembolic Disease, and Shock, pp. 128-130. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Blood And Bone Marrow Disease, pp. 582-583.

Q: Level of which of the following is not elevated in heart disease

5-nucleotidase. ***5-nucleotidase*** - While other enzymes like LDH, SGOT, and ALP can be elevated in various conditions including heart disease (especially in the context of tissue damage), 5-nucleotidase is **not typically elevated in heart disease**. - Its elevation is more commonly associated with **biliary obstruction** or certain liver pathologies. *LDH* - **Lactate dehydrogenase (LDH)** is a marker of **cellular damage** and can be elevated in myocardial infarction, though it is less specific than troponins. - LDH levels rise later than CK-MB and remain elevated longer, indicating persistent tissue injury. *SGOT* - **Serum glutamic oxaloacetic transaminase (SGOT)**, also known as **aspartate aminotransferase (AST)**, is elevated in acute **myocardial infarction** due to cardiac muscle damage. - While it's a marker for cardiac injury, it's not specific as it's also highly concentrated in the liver. *ALP* - **Alkaline phosphatase (ALP)** can be mildly elevated in heart failure due to **hepatic congestion** caused by reduced cardiac output. - While its primary diagnostic significance is in bone and liver disease, its elevation in advanced heart disease is usually a secondary consequence.

Q: What is the estimated blood glucose level in mg/dL for a patient with an HbA1c of 8% based on the conversion formula?

200. ***200*** - The estimated average glucose (eAG) can be calculated from HbA1c using the formula: **eAG (mg/dL) = 28.7 × HbA1c (%) – 46.7**. - For an HbA1c of 8%, the calculation is: **28.7 × 8 – 46.7 = 229.6 – 46.7 = 182.9 mg/dL**, which is closest to 200 mg/dL among the given options. *120* - An eAG of 120-125 mg/dL would correspond to an **HbA1c between 5.8% and 6.0%**, which is below the given 8%. - This value typically reflects **well-controlled or pre-diabetic** blood glucose levels. *160* - An eAG of 160 mg/dL would correspond to an **HbA1c of approximately 7.0-7.2%**, which is lower than the given 8%. - This level is often the target for HbA1c in many **diabetic management guidelines**, but not for 8%. *240* - An eAG of 240 mg/dL would correspond to an **HbA1c of approximately 9.9%**, which is significantly higher than the given 8%. - This indicates **poorly controlled diabetes** and a much higher average blood glucose level.

Q: Cystatin C levels are used for

Estimating GFR. ***Estimating GFR*** - **Cystatin C** is a **proteinase inhibitor** produced by all nucleated cells at a constant rate, and its level in the blood is inversely related to the **glomerular filtration rate (GFR)**. - Unlike **creatinine**, Cystatin C levels are less affected by **muscle mass, diet, or inflammation**, making it a more reliable marker for early and subtle changes in GFR, especially in certain populations. *Detecting UTI* - **Urinary tract infections (UTIs)** are primarily detected through **urinalysis** (presence of **leukocytes, nitrites**, and **bacteria**) and **urine culture**. - **Cystatin C** is a serum marker for renal function and has no direct role in detecting the presence of bacterial infection in the urinary tract. *Estimating difference between CRF and ARF* - Differentiating between **chronic renal failure (CRF)** and **acute renal failure (ARF)** typically involves assessing the **chronicity of symptoms**, trend in **creatinine levels**, and **kidney size** and **echogenicity** on ultrasound. - While Cystatin C can reflect current GFR, it doesn't inherently provide discriminatory power between acute and chronic processes without serial measurements or additional clinical context. *Screening for Renal Ca* - **Renal cell carcinoma (RCC)** screening is primarily done using **imaging techniques** like **ultrasonography, CT, or MRI**, especially in individuals with risk factors or symptoms like **hematuria**. - **Cystatin C** is a marker of kidney function and does not serve as a tumor marker for renal cancer.

Q: Which of the following is not an acute phase reactant?

Endothelin. ***Endothelin*** - Endothelin is a **vasoconstrictive peptide** primarily involved in regulating **blood vessel tone** and blood pressure. - While it plays a role in processes like inflammation and tissue repair, it is not synthesized or regulated in the same rapid, systemic manner as a classic acute phase reactant. *C-reactive protein* - **C-reactive protein (CRP)** is a rapidly responding acute phase reactant produced by the liver in response to **inflammation**, infection, and tissue injury. - Its levels can rise dramatically within hours of an inflammatory stimulus and are used as a marker for disease activity. *Haptoglobin* - **Haptoglobin** is an acute phase reactant that binds to free **hemoglobin** released from red blood cells during hemolysis, preventing oxidative damage. - Its levels typically increase during acute inflammation or infection, although it can also decrease with severe hemolysis. *Fibrinogen* - **Fibrinogen** is a critical acute phase protein involved in the **coagulation cascade** and wound healing. - Its concentration increases significantly during acute inflammation, contributing to the elevated **erythrocyte sedimentation rate (ESR)**.

Question 1

Which of the following is a synthetic oxygen carrier?

Accepted Answer

Perfluorocarbon

Answer

Chlorofluorocarbon

Answer

1-fluoro-2,4-dinitrophenol

Answer

2,4-dinitrophenol

Question 2

Cataract in cases of diabetes mellitus is due to accumulation of ?

Accepted Answer

Glycated crystallins

Answer

Calcified crystallins

Answer

Glycated fibrillins

Answer

Calcified fibrillins

Question 3

Bilirubin in serum can be measured by

Accepted Answer

Van den Bergh reaction

Answer

Ehrlich’s Reaction

Answer

Schlesinger’s Reaction

Answer

Fouchet's Reaction

Question 4

In which condition is 5-Hydroxyindoleacetic acid (HIAA) elevated in urine?

Accepted Answer

Carcinoid

Answer

Alkaptonuria

Answer

Albinism

Answer

Phenylketonuria

Question 5

Which of the following is a positive acute phase protein that enhances the acute phase response?

Accepted Answer

Fibrinogen

Answer

Transferrin

Answer

Albumin

Answer

Prealbumin

Question 6

Converging point of both pathways in coagulation is at:

Accepted Answer

Stuart factor X

Answer

Factor VIII

Answer

Factor IX

Answer

Factor VII

Question 7

Level of which of the following is not elevated in heart disease

Accepted Answer

5-nucleotidase

Answer

SGOT

Answer

ALP

Answer

LDH

Question 8

What is the estimated blood glucose level in mg/dL for a patient with an HbA1c of 8% based on the conversion formula?

Accepted Answer

200

Answer

120

Answer

160

Answer

240

Question 9

Cystatin C levels are used for

Accepted Answer

Estimating GFR

Answer

Detecting UTI

Answer

Screening for Renal Ca

Answer

Estimating difference between CRF and ARF

Question 10

Which of the following is not an acute phase reactant?

Accepted Answer

Endothelin

Answer

C-reactive protein

Answer

Haptoglobin

Answer

Fibrinogen

Clinical Biochemistry — MCQs

Clinical Biochemistry — MCQs

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