Estimation of Serum SGPT

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Introduction

  • Estimation of Serum SGPT stands for Serum Glutamic Pyruvic Transaminase.
  • It is now commonly called ALT (Alanine Aminotransferase).
  • ALT is an intracellular enzyme mainly present in:
  • liver
  • kidney
  • heart
  • skeletal muscle
  • ALT catalyzes transfer of amino group from alanine to α-ketoglutarate.
  • It plays an important role in amino acid metabolism.
  • ALT is more specific for liver injury than AST because it is concentrated mainly in hepatocytes.
  • When liver cells are damaged, ALT is released into blood and serum level rises.
  • Therefore, serum ALT levels are among the most important liver function tests.

Principle

  • Serum ALT estimation is based on the IFCC kinetic method.
  • ALT catalyzes transfer of amino group from L-alanine to α-ketoglutarate.

L-Alanine + 2-oxoglutarate ———> ALT/GPT  ————>Pyruvate + L-Glutamate  

Pyruvate + NADH  —————–>LDH ——————> L-Lactate + NAD+    

Sample pyruvate + NADH  ——–>LDH ——————>L-Lactate + NAD

  • In the presence of SGPT, alanine transfers its amino group to α-ketoglutarate, producing pyruvate and glutamate.
  • Pyruvate is then reduced to lactate by lactate dehydrogenase (LDH) with the simultaneous oxidation of NADH to NAD⁺.
  • The rate of decrease in NADH absorbance at 340 nm is proportional to SGPT activity.

Samples

  • Sample Type: Serum or plasma (collected in heparinized tubes).
  • Sample Volume: ~0.5 mL.
  • Storage: Samples should be analyzed within 24 hours. If not processed immediately, store at 2–8°C for up to 48 hours. Prolonged storage may affect enzyme activity.

Reagents

Reagent Composition Concentration
R1 Tris Buffer (pH 7.5) 137.5 mmol/L
L-Alanine 709 mmol/L
LDH (microbial) ≥ 2000 U/L
R2 CAPSO 20 mmol/L
2-Oxoglutarate 85 mmol/L
NADH 1.05 mmol/L

Procedure

Reagent 1 (buffer) 1 ml
Sample 0.100 ml

Mix and incubate for 5 min. at 37°C. Then add
Reagent 2 (substrate) 0.250 ml
  • Mix, incubate 1 min. At 37°C, measure the calibrator’s initial absorbance and sample against the reagent blank.
  • Measure the absorbance change exactly after 1, 2, and 3 min.
  • Calculate a 1-minute absorbance change (ΔA/min).

Calculation

SGPT activity is expressed in units per litre (U/L). The calculation is based on the change in absorbance per minute (ΔA/min):

SGPT (U/L) = ΔA/min × Vt × 1000/ϵ × d × Vs ​

Where:

    • Vt: Total reaction volume (mL)
    • Vs​: Sample volume (mL)
    • ϵ: Molar extinction coefficient of NADH (6.22 L/mmol/cm)
    • d: Path length of cuvette (cm)

Normal Range

  • Adults: 7–56 U/L
  • Children: Slightly higher values due to active growth.
    Note: Normal ranges may vary depending on the laboratory and assay method.

Clinical Significance

Increased SGPT (ALT)

  • Increased serum ALT usually indicates hepatocellular damage.

Liver Diseases

  • ALT rises significantly in liver cell injury.

Seen in:

  • acute viral hepatitis
  • chronic hepatitis
  • fatty liver disease
  • liver cirrhosis
  • drug-induced liver injury
  • toxic hepatitis

Clinical Importance

  • ALT often rises markedly in acute hepatitis
  • ALT is usually higher than AST in viral hepatitis

Fatty Liver Disease

  • ALT commonly increases in fatty liver associated with obesity, diabetes, and metabolic syndrome.

Drug-Induced Liver Injury

  • Many drugs cause hepatocyte damage and raise ALT.

Common Drugs

  • paracetamol overdose
  • antibiotics
  • antitubercular drugs

Alcoholic Liver Disease

  • ALT may rise, but AST usually rises more than ALT.

Muscle Injury

  • Mild ALT rise may occur in severe muscle injury, but less than AST.

Diagnostic Importance

  • ALT is one of the most important liver function tests (LFTs).
  • It helps detect early liver injury.
  • Used to monitor liver disease progression and treatment response.

ALT / AST Comparison

  • ALT > AST → viral hepatitis / hepatocellular injury
  • AST > ALT → alcoholic liver disease

MCQs

1. SGPT stands for:

A. Serum Glucose Pyruvate Test
B. Serum Glutamic Pyruvic Transaminase
C. Serum General Protein Test
D. Serum Glucose Phosphate Transferase
Answer: B. Serum Glutamic Pyruvic Transaminase

2. Another name of SGPT is:

A. AST
B. ALT
C. ALP
D. ACP
Answer: B. ALT

3. ALT stands for:

A. Alanine Aminotransferase
B. Aspartate Transferase
C. Alanine Test
D. Amino Liver Test
Answer: A. Alanine Aminotransferase

4. SGPT is mainly present in:

A. Liver
B. Kidney
C. Heart
D. All of the above
Answer: D. All of the above

5. SGPT is more specific for:

A. Kidney disease
B. Liver disease
C. Heart disease
D. Brain disease
Answer: B. Liver disease

6. Principle of SGPT estimation is based on:

A. IFCC kinetic method
B. GOD-POD method
C. Jaffe method
D. Biuret method
Answer: A. IFCC kinetic method

7. Main substrate used in ALT reaction:

A. L-alanine
B. Aspartate
C. Glucose
D. Urea
Answer: A. L-alanine

8. ALT transfers amino group to:

A. Lactate
B. α-ketoglutarate
C. Citrate
D. Oxaloacetate
Answer: B. α-ketoglutarate

9. Product formed in first reaction:

A. Oxaloacetate
B. Pyruvate
C. Lactate
D. Malate
Answer: B. Pyruvate

10. Coupled enzyme used:

A. LDH
B. MDH
C. Urease
D. Peroxidase
Answer: A. LDH

11. LDH stands for:

A. Lactate Dehydrogenase
B. Liver Dehydrogenase
C. Lipid Dehydrogenase
D. Long Dehydrogenase
Answer: A. Lactate Dehydrogenase

12. Pyruvate converts into:

A. Lactate
B. Malate
C. Citrate
D. Oxaloacetate
Answer: A. Lactate

13. NADH converts into:

A. NADP
B. NAD⁺
C. ATP
D. ADP
Answer: B. NAD⁺

14. Absorbance is measured at:

A. 405 nm
B. 500 nm
C. 340 nm
D. 650 nm
Answer: C. 340 nm

15. SGPT estimation measures:

A. Increase in absorbance
B. Decrease in absorbance
C. Color intensity
D. Turbidity
Answer: B. Decrease in absorbance

16. Preferred sample:

A. Serum
B. Urine
C. Whole blood
D. Saliva
Answer: A. Serum

17. Hemolyzed sample:

A. Preferred
B. Avoided
C. Heated
D. Frozen
Answer: B. Avoided

18. Sample volume commonly used:

A. 10 µL
B. 50 µL
C. 100 µL
D. 500 µL
Answer: C. 100 µL

19. Working reagent volume:

A. 500 µL
B. 1000 µL
C. 2000 µL
D. 250 µL
Answer: B. 1000 µL

20. Incubation temperature:

A. 25°C
B. 30°C
C. 37°C
D. 45°C
Answer: C. 37°C

21. First incubation time:

A. 1 minute
B. 10 minutes
C. 20 minutes
D. 30 seconds
Answer: A. 1 minute

22. Readings are taken at:

A. 1, 2, 3 minutes
B. 5 and 10 minutes
C. Single reading
D. End point only
Answer: A. 1, 2, 3 minutes

23. ΔA/min means:

A. Total absorbance
B. Change in absorbance per minute
C. Standard absorbance
D. Blank absorbance
Answer: B. Change in absorbance per minute

24. Common factor for ALT:

A. 1746
B. 3128
C. 1000
D. 200
Answer: A. 1746

25. SGPT rises in:

A. Hepatitis
B. Fatty liver
C. Drug-induced liver injury
D. All of the above
Answer: D. All of the above

26. ALT is higher than AST in:

A. Viral hepatitis
B. Alcoholic liver disease
C. Muscle injury
D. Hemolysis
Answer: A. Viral hepatitis

27. AST is higher than ALT in:

A. Viral hepatitis
B. Alcoholic liver disease
C. Fatty liver
D. Renal disease
Answer: B. Alcoholic liver disease

28. ALT is part of:

A. Lipid profile
B. Liver function test
C. Renal function test
D. Thyroid profile
Answer: B. Liver function test

29. Normal ALT in adult male:

A. Up to 45 U/L
B. Up to 100 U/L
C. Up to 10 U/L
D. Up to 70 U/L
Answer: A. Up to 45 U/L

30. Normal ALT in adult female:

A. Up to 34 U/L
B. Up to 50 U/L
C. Up to 70 U/L
D. Up to 20 U/L
Answer: A. Up to 34 U/L

Short MCQs (31–50)

  1. SGPT full form = Serum Glutamic Pyruvic Transaminase
  2. Modern name = ALT
  3. Main organ for ALT = Liver
  4. Main wavelength = 340 nm
  5. Coupled enzyme = LDH
  6. Coenzyme = NADH
  7. Product = Pyruvate
  8. Sample type = Serum
  9. Method = Kinetic
  10. ALT useful in LFT = Yes
  11. ALT rises in hepatitis = Yes
  12. ALT rises in fatty liver = Yes
  13. ALT rises in drug toxicity = Yes
  14. ALT more specific than AST = Yes
  15. Hemolysis affects ALT = Yes
  16. ALT factor common = 1746
  17. ALT decreases absorbance = Yes
  18. ALT substrate = Alanine
  19. ALT diagnostic use = Liver injury
  20. ALT routine biochemical test = Yes
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