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Stool chymotrypsin activity measured by a spectrophotometric procedure to identify pancreatic disease in infants
Insights
The BMC stool chymotrypsin test accurately diagnoses pancreatic disease in infants. This enzyme assay shows good recovery and precision, with triplicate sampling recommended for reliable results in pediatric patients.
Area of Science:
- Pediatric Gastroenterology
- Clinical Chemistry
- Enzyme Assays
Background:
- Pancreatic disease diagnosis in infants requires accurate stool analysis.
- Chymotrypsin is a key enzyme marker for pancreatic exocrine function.
- Existing diagnostic methods may have limitations in pediatric populations.
Purpose of the Study:
- To evaluate the analytical performance of the BMC stool chymotrypsin test.
- To assess the test's accuracy in diagnosing pancreatic disease in infants.
- To establish optimal sample handling procedures for reliable results.
Main Methods:
- The BMC stool chymotrypsin test was performed using spectrophotometry to measure enzyme activity.
- Analytical performance was assessed through recovery, imprecision, and linearity studies.
- The test was applied to 220 consecutive stool samples from children.
Main Results:
- The assay demonstrated good recovery (80-105%) and low imprecision (CV 2.2-5.2%).
- Linearity was observed up to 600 U/g stool.
- Triplicate stool sampling was recommended due to enzyme inhomogeneity (4.2-150% range).
Conclusions:
- The BMC stool chymotrypsin test is analytically sound for pediatric use.
- The test shows potential for diagnosing pancreatic insufficiency, including in cystic fibrosis (CF).
- Standardized triplicate sampling is crucial for accurate diagnosis.
Abstract:
The aim of this study was to assess the analytical performance of the BMC stool chymotrypsin test and its accuracy in diagnosing pancreatic disease in infants. The test utilizes a detergent which solubilizes chymotrypsin bound to stool residues, and a tetrapeptide coupled to p-nitroaniline which is specifically cleaved by chymotrypsin. We employed the IL Multistat at 30 degrees C to monitor enzyme activity as an increase in absorbance at 405 nm. The reaction was linear to 600 U/g stool. Recovery of exogenous chymotrypsin with a single detergent extraction was 98-105%, and of endogenous chymotrypsin (as determined by multiple extractions) 80-97%. Imprecision (CV) was 2.2% within-day and 2.4% between-day for the BMC control, and 2.4-5.2% for stool chymotrypsin in the range 8.3-14.4 U/g. Since the test utilises only 100 mg of stool, inhomogeneity of enzyme distribution was assessed by multiple assays on a single stool, which revealed a range of activity from 4.2-150%. We therefore recommend sampling of each stool in triplicate. With this procedure, chymotrypsin was measured in 220 consecutive stool samples submitted for fat determination from children. Applying the manufacturer's lower reference limit of 4.1 U/g, the following results were obtained (number abnormal/total number): suspected intestinal disease with normal stool fat (5/127); proven intestinal disease and increased stool fat (1/26); untreated cystic fibrosis (CF) with (19/22), and without (0/3) steatorrhea; CF with pancreatic insufficiency on replacement therapy (4/42).(ABSTRACT TRUNCATED AT 250 WORDS)