Clinical Biochemistry Practice Questions

Q: A 50-year-old male with family history for type 2 diabetes underwent a urine test for reducing substances. The test tube containing 0.5 ml of urine and 5 ml Benedict's reagent was put in a water bath for 2 minutes and change in colour of tube was noticed. Which is the correct statement about the concentration of sugar in the test tube?

2 % sugar. ***2 % sugar*** - A red or brick-red precipitate in Benedict's test indicates a **very high concentration of reducing sugars**, typically **2% or greater** - This represents the most intense positive reaction with **complete reduction of cupric ions (Cu²⁺) to cuprous oxide (Cu₂O)**, producing the characteristic brick-red color - In clinical context, such high urinary glucose indicates **severe hyperglycemia** requiring immediate evaluation *0.5 % sugar* - A 0.5% sugar concentration produces a **green or yellowish-green precipitate**, indicating a trace to moderate amount of reducing sugar - This represents **partial reduction** of the Benedict's reagent with less intense color change - Clinically significant but suggests better glycemic control than higher concentrations *1 % sugar* - A 1% sugar concentration produces an **orange or yellow-orange precipitate**, indicating significant glycosuria - This intermediate color reflects **moderate reduction** of cupric ions - While this indicates poor glycemic control, it is less severe than the 2% concentration *1.5 % sugar* - A 1.5% sugar concentration produces a **reddish-orange precipitate**, approaching but not reaching brick-red intensity - This represents **substantial but incomplete maximal reduction** of the reagent - The distinction from 2% lies in the color intensity - reddish-orange versus pure brick-red

Q: A sample of 5 mL urine of the patient was taken and aqueous solution of picric acid was added to it. The solution was made alkaline using NaOH and the following colour was produced. The test is called?

Jaffe's reaction. ***Jaffe's reaction*** - This test describes the **Jaffe reaction**, a colorimetric method used to detect **creatinine** by reacting it with **picric acid** in an alkaline environment, producing an orange-red color. - The intensity of the **orange-red color** is directly proportional to the amount of creatinine present in the urine sample. *Benedict's test* - **Benedict's test** is used to detect the presence of **reducing sugars**, such as glucose, in urine. - This test involves heating the sample with Benedict's reagent, and a color change from blue indicates the presence of reducing sugars. *Guthrie's test* - **Guthrie's test** is a **bacterial inhibition assay** used for newborn screening to detect metabolic disorders, most notably **phenylketonuria (PKU)**. - It involves placing a blood spot on a culture plate with bacteria and an inhibitor; growth around the blood spot indicates the presence of specific metabolites. *Friedel-Crafts reaction* - The **Friedel-Crafts reaction** is a set of organic reactions that involve the **alkylation** or **acylation** of aromatic compounds. - This reaction is primarily used in organic synthesis and is not a biochemical test for urine analysis.

Q: Which of the following tubes contain sodium fluoride as an anti-coagulant?

Gray-top tube. ***a. Gray-top tube*** - The **gray-top tube** contains **sodium fluoride** and **potassium oxalate** as anticoagulants. - Sodium fluoride acts as both an **anticoagulant** and an **antiglycolytic agent**, preserving glucose concentration by inhibiting glycolysis. - This tube is the **standard choice for glucose testing** in clinical laboratories. *b. Green-top tube* - The **green-top tubes** contain **heparin** (either sodium, lithium, or ammonium heparin) as an anticoagulant. - These tubes are used for various tests including **plasma chemistry** and some hormone assays, but not for glucose preservation with sodium fluoride. *c. Pink-top tube* - The **pink-top tube** generally contains **EDTA** (ethylenediaminetetraacetic acid) and is specifically designed for **blood bank** tests due to its special labeling and anticoagulant properties for cross-matching. - While it contains an anticoagulant, it is not sodium fluoride and is not used for glucose measurement. *d. Blue-top tube with yellow checkerboard pattern* - While some manufacturers may use different labeling systems, the **standard tube for sodium fluoride** is the gray-top tube, not the blue-top with checkerboard pattern. - Blue-top tubes typically contain **sodium citrate** and are used for coagulation studies (PT, PTT, INR).

Q: Which one of the following conditions can be screened during neonatal screening by biochemical tests?

Congenital hypothyroidism. ***Congenital hypothyroidism*** - **Neonatal screening** for congenital hypothyroidism is a standard practice, using biochemical tests to measure **thyroid-stimulating hormone (TSH)** and **thyroxine (T4)** levels in dried blood spots. - Early detection and treatment prevent severe **intellectual disability** and developmental delays caused by thyroid hormone deficiency. *Congenital dislocation of hip* - This condition is primarily screened through **physical examination** (e.g., Ortolani and Barlow maneuvers) and imaging (e.g., ultrasound), not biochemical tests. - It involves a structural abnormality of the hip joint, not a metabolic or biochemical disorder. *Congenital rubella* - Diagnosis of congenital rubella involves detecting **rubella-specific IgM antibodies** or viral RNA, which are immunological/virological tests, not typical biochemical screening. - This is an infectious disease, not an inborn error of metabolism screened biochemically. *Chromosomal abnormalities* - Conditions like Down syndrome (Trisomy 21) are detected through **karyotyping** or **genetic tests**, which examine the number and structure of chromosomes. - While some biochemical markers are used in prenatal screening for chromosomal abnormalities (e.g., quad screen), direct neonatal screening for chromosomal abnormalities is not performed via general biochemical tests.

Q: A urine sample shows a maroon-colored ring at the interface of two layers after adding reagents. Identify the test:

Rothera's test. ***Rothera's test*** - The image displays a **maroon-colored ring** at the interface of two layers, which is a characteristic positive result for Rothera's test. - Rothera's test is used to detect the presence of **ketone bodies**, specifically **acetone and acetoacetate**, in urine. *Benedict's test* - Benedict's test is used to detect **reducing sugars**, such as glucose, in urine. - A positive Benedict's test typically produces a color change from blue to green, yellow, orange, or brick-red precipitate after heating, which is not what is seen here. *Biuret test* - The Biuret test is used to detect **peptide bonds** and thus the presence of **proteins**. - A positive Biuret test results in a **violet or purple color** when proteins are present, which is different from the reaction shown. *Fehling's test* - Fehling's test is another test used to detect the presence of **reducing sugars** in a sample. - A positive result is indicated by the formation of a **brick-red precipitate** of cuprous oxide after heating, which is not consistent with the image.

Q: Preferred biochemical marker(s) in patients presenting with myocardial infarction:

Cardiac specific Troponins. ***Cardiac specific Troponins*** - **Cardiac troponins** (cTnI and cTnT) are the preferred and most sensitive and specific biomarkers for diagnosing **myocardial infarction (MI)**. - They are proteins released into the bloodstream when myocardial cells are damaged, and their levels rise within hours of MI onset and remain elevated for several days. *All of the options* - While other markers like **CK-MB** and **Myoglobin** were historically used, **cardiac troponins** have superior specificity and sensitivity for MI. - The latest guidelines from major cardiology societies recommend troponins as the primary diagnostic markers. *Myoglobin* - **Myoglobin** is an early marker, but it is not specific to cardiac muscle and can be elevated in various conditions involving skeletal muscle damage. - Its short half-life means it can return to normal quickly, making it less reliable for diagnosing MI, especially if there's a delay in presentation. *CK-MB* - **Creatine Kinase-MB (CK-MB)** is a more specific marker than total CK for cardiac muscle damage but is still less specific than cardiac troponins. - It can be elevated in conditions like **myocarditis** or **pericarditis**, and its levels typically peak and decline earlier than troponins, limiting its diagnostic window.

Q: In a child presenting with obstructive jaundice all are elevated EXCEPT:

Glutamate dehydrogenase. ***Glutamate dehydrogenase*** - **Glutamate dehydrogenase (GLDH)** is an enzyme primarily found in the mitochondria of hepatocytes and is a marker of **hepatocellular damage**, not cholestasis or biliary obstruction. - While other enzymes are elevated in obstructive jaundice, GLDH elevation indicates **liver cell injury**, which is typically not the primary problem in pure obstruction. *5' Nucleotidase* - **5' nucleotidase** is a canalicular enzyme and its elevation is a **specific indicator of cholestasis** and biliary obstruction. - Its concentration is increased in conditions where there is **impaired bile flow**, making it a useful marker for obstructive jaundice. *Alkaline phosphatase* - **Alkaline phosphatase (ALP)** is an enzyme found in the liver (biliary ducts) and bone, and a significant increase in its levels is a key feature of **obstructive jaundice**. - High ALP levels indicate **biliary obstruction** or cholestasis due to impaired bile flow. *Gamma glutamyl transpeptidase* - **Gamma-glutamyl transpeptidase (GGT)** is an enzyme found in various tissues, including the liver, and its elevation is a **sensitive marker for cholestasis** and biliary obstruction. - GGT levels are typically elevated in parallel with ALP in diseases affecting the **bile ducts**, confirming the hepatic origin of elevated ALP.

Question 1

A 10-year-old boy presents with increased bilirubin, bilirubin in urine, and no urobilinogen. What is the most likely diagnosis?

Accepted Answer

Obstructive jaundice

Answer

Gilbert syndrome

Answer

Hemolytic jaundice

Answer

Viral hepatitis

Question 2

Which condition is characterized by hypocalcemia with hyperphosphatemia?

Accepted Answer

Chronic Renal Failure (CRF)

Answer

Pseudohypoparathyroidism

Answer

Vitamin D deficiency

Answer

Vitamin D deficiency

Question 3

Cerebrospinal fluid (CSF) is best stored at which temperature?

Accepted Answer

4°C

Answer

-20°C

Answer

Room temperature

Answer

-70°C

Question 4

A 50-year-old male with family history for type 2 diabetes underwent a urine test for reducing substances. The test tube containing 0.5 ml of urine and 5 ml Benedict's reagent was put in a water bath for 2 minutes and change in colour of tube was noticed. Which is the correct statement about the concentration of sugar in the test tube?

Accepted Answer

2 % sugar

Answer

0.5 % sugar

Answer

1 % sugar

Answer

1.5 % sugar

Question 5

A sample of 5 mL urine of the patient was taken and aqueous solution of picric acid was added to it. The solution was made alkaline using NaOH and the following colour was produced. The test is called?

Accepted Answer

Jaffe's reaction

Answer

Benedict's test

Answer

Guthrie's test

Answer

Friedel-Crafts reaction

Question 6

Which of the following tubes contain sodium fluoride as an anti-coagulant?

Accepted Answer

Gray-top tube

Answer

Green-top tube

Answer

Pink-top tube

Answer

Blue-top tube with yellow checkerboard pattern

Question 7

Which one of the following conditions can be screened during neonatal screening by biochemical tests?

Accepted Answer

Congenital hypothyroidism

Answer

Congenital dislocation of hip

Answer

Congenital rubella

Answer

Chromosomal abnormalities

Question 8

A urine sample shows a maroon-colored ring at the interface of two layers after adding reagents. Identify the test:

Accepted Answer

Rothera's test

Answer

Benedict's test

Answer

Biuret test

Answer

Fehling's test

Question 9

Preferred biochemical marker(s) in patients presenting with myocardial infarction:

Accepted Answer

Cardiac specific Troponins

Answer

All of the options

Answer

Myoglobin

Answer

CK-MB

Question 10

In a child presenting with obstructive jaundice all are elevated EXCEPT:

Accepted Answer

Glutamate dehydrogenase

Answer

5' Nucleotidase

Answer

Alkaline phosphatase

Answer

Gamma glutamyl transpeptidase

Clinical Biochemistry — MCQs

Clinical Biochemistry — MCQs

On this page

Practice by Chapter

Want unlimited practice?