Stool Trypsin Test

 


1. Objective

To detect the presence or absence of trypsin enzyme activity in the stool, which helps in the screening of cystic fibrosis (CF) in newborns and infants by identifying pancreatic enzyme insufficiency.

2. Principle

Trypsin is a pancreatic proteolytic enzyme that breaks down proteins. In cystic fibrosis, thick mucus blocks pancreatic ducts, reducing enzyme secretion (including trypsin) into the gut.

The test is based on the enzyme's ability to hydrolyze specific protein substrates (e.g., gelatin or casein) in a gelatin film or x-ray film or chromogenic substrate in a colorimetric test.

3. Materials

  • Fresh stool sample (no preservatives)

  • Filter paper or x-ray film coated with gelatin

  • Positive and negative control strips

  • Dropper or swab

  • Buffer or sterile water

  • Timer

  • PPE (gloves, lab coat)

4. Procedure (Film Method)

  • Collect a pea-sized stool sample.

  • Mix with sterile water to make a suspension.

  • Apply a drop onto a gelatin-coated film (x-ray film or test card).

  • Incubate at 37°C for 30–60 minutes.

  • Rinse with water and observe for clearing or digestion of gelatin.

5. Result Interpretation

ObservationInterpretation
Clear zone on filmTrypsin present (Normal — no CF)
No clearingTrypsin absent (Suggests pancreatic insufficiency — possible CF)


6. Uses

  • Screening tool for cystic fibrosis, especially in newborns

  • Identify exocrine pancreatic insufficiency

  • May supplement other tests like:

    • Sweat chloride test (gold standard for CF)

    • Fecal elastase (alternative enzyme-based test)

7. Conclusion

The Stool Trypsin Test is a quick, inexpensive screening method for pancreatic dysfunction due to cystic fibrosis. While it has largely been replaced by more sensitive tests (like fecal elastase or genetic testing), it still serves in basic or resource-limited settings.

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