Questions and Answers
What is the significance of urine bilirubin in differential diagnosis of jaundice?
What is the primary source of alkaline phosphatase in normal adult serum?
Which of the following is NOT a characteristic of AST and ALT?
What is the primary role of AST and ALT in the body?
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What is the clinical significance of elevated total serum bilirubin above 40 mg/dl?
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Which of the following organs has a significant contribution to alkaline phosphatase in serum during pregnancy?
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What is the primary activator of alkaline phosphatase?
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Which of the following is NOT a characteristic of bilirubinuria?
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What is the significance of measuring AST and ALT activity in serum?
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During childhood, what is the primary source of alkaline phosphatase?
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Study Notes
Uric Acid Concentration in Serum and Urine
- Uric acid levels are affected by exercise and diet containing purine
- Normal uric acid excretion occurs through urine, and increased levels in blood are accompanied by increased excretion in urine
- Elevated uric acid levels are seen in several diseases, including:
- Renal failure
- Leukemia
- Multiple myeloma
- Lymphoma
- Glycogenesis
- Chronic hemolytic anemia
- Pernicious anemia
- Lymphosarcoma
- Specifically, uric acid levels can increase up to 6.5-12 mg/dl in gout, where uric acid is deposited as crystals in joints
Estimation of Total Calcium in Serum and Urine
- Calcium is the most abundant mineral cation in the body, making up 1-1.5 kg of total body weight in adults
- 50% of total plasma calcium exists in ionized form, which is functionally most active
- Calcium binds to negatively charged sites on proteins in a pH-dependent manner
- Alkaline conditions promote calcium binding and decrease free calcium, whereas acidic conditions decrease calcium binding and increase free calcium levels
- Clinical significance:
- Calcium levels are increased in hyperparathyroidism
- Hypocalcemia is a more serious and life-threatening condition than hypercalcemia
- In rickets, the product of serum calcium and phosphorus decreases, usually below 30 mg/dl
- An increase in alkaline phosphatase activity is a characteristic feature of rickets
Estimation of Inorganic Phosphorus in Serum and Urine
- Phosphorus has two forms: organic and inorganic
- Inorganic phosphorus is present in the blood as phosphates of alkaline and alkali earth metals (H2PO4 and HPO4-2)
- The ratio of H2PO4 and HPO4-2 is pH-dependent
- Organic phosphorus includes glycerophosphates, nucleotide phosphate, and hexose phosphate
Estimation of Total Cholesterol in Serum
- Cholesterol is a precursor of:
- Vitamin D
- Steroid hormones
- Bile acids
Estimation of Total and Direct Bilirubin in Serum
- Bilirubin metabolism involves the conversion of heme to bilirubin in reticuloendothelial cells
- Unconjugated bilirubin is transported to the liver, where it is conjugated with glucuronic acid to form conjugated bilirubin
- Conjugated bilirubin is water-soluble and excreted through the bile
- Clinical significance:
- In hemolytic jaundice, unconjugated bilirubin is increased due to increased destruction of red blood cells
- In hepatic jaundice, conjugated bilirubin decreases along with decreased excretion of bilirubin
- In posthepatic jaundice, the concentration of conjugated bilirubin is increased compared to unconjugated bilirubin
- Total serum bilirubin amount >40 mg/dl indicates hepatocellular obstruction and not extrahepatic obstruction
- Urine bilirubin and urobilinogen are important in differential diagnosis of jaundice
Determination of Alanine and Aspartate Transaminase Activity in Serum (AST & ALT)
- These enzymes catalyze the reversible transfer of the α-amino group from amino acids to α-keto acids
- They are present in almost all cells, but higher amounts occur mainly in the liver, brain, heart, and kidney
- Two clinically important transaminases are:
- Glutamine oxaloacetate transaminase (SGOT), also called aspartate aminotransferase (AST)
- Glutamine pyruvate transaminase (SGPT), also called alanine aminotransferase (ALT)
- The measurement of these enzymes is a useful diagnosis indicator of liver functions
Estimation of Alkaline Phosphatase Activity in Serum
- ALP of normal serum in adults is mainly derived from the liver and bone, with small amounts from the intestinal component
- During childhood, the majority of alkaline phosphatase is of skeletal origin
- During pregnancy, ALP is also contributed from the placenta
- ALP is activated by magnesium ions
- Clinical significance:
- Elevated ALP levels are seen in various diseases, including bone diseases and liver diseases
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Description
This quiz determines the clinical significance of uric acid levels in serum and urine, including its correlation with diseases such as renal failure and anemia. It also covers the effects of exercise and diet on uric acid levels.
