Elastase-I is a protease produced in acinar cells of the pancreas. Low concentrations in the stool are associated with exocrine pancreatic insufficiency (EPI). It is a useful screening test but has false positive and false negative results.
Testing units: micrograms per gram stool
Test Result
Interpretation
> 200 µg/g
normal (negative)
100 to 200 µg/g
indeterminate
< 100 µg/g
reduced (positive)
Vanga et al reported a sensitivity of 0.77 and specificity of 0.88. While respectable as a screening test, it is not diagnostic by itself. The reliability of the test is affected by the pre-test probability of the patient.
Pre-Test Probability
Positive Test Result
Negative Test Result
low
rule out false positive
rules out EPI
high
rules in EIP
rule out false negative
If an unexpected positive or negative result is obtained, then additional testing needs to be performed.
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