Eligibility criteria consisted of (1) clinical studies published in peer-reviewed English-language journals, with no restriction as to year of publication, (2) either serum levels of trypsinogen-1, trypinogen-2, TAP or trypsin were assessed in patients with AP, and (3) serum levels of the aforementioned markers were put in relation to the severity of AP. This evidence concerns the gene PRSS1 and alkaline phosphatase measurement.