Acute Pancreatitis (AP) is an inflammatory condition of the pancreas, presenting initially as severe upper abdominal pain. This disease can range from mild AP to moderately severe or severe AP, with development of local and systemic complications and a diverse range of outcomes. Consequently, it is imperative to diagnose and predict disease severity at the earliest juncture. Numerous guidelines exist for the management of AP, including the revised Atlanta classification system. This guideline does not have the capacity to predict the degree of disease severity from hospital admission. Thus, the availability of a predictive biomarker, working in conjunction with the established classification system, would be advantageous. Several markers such as amylase, lipase and C-reactive protein are used for the diagnosis of AP by hospitals at present. However, it is now fundamentally agreed that the early intrapancreatic activation of normal protein digestion enzymes is associated with development of AP. Trypsinogen Activation Peptide (TAP) is a potential predictive biomarker of AP that is proportionally produced and rapidly excreted into the urine following cleavage of the zymogen, trypsinogen, to trypsin. Herein, the establishment of a gold standard ELISA (with an intra- and inter-assay coefficient of variation of 1.7 – 10.1% and 4.8 – 10.4%, respectively) and the development of a lateral flow test strip for urinary TAP are described. An exploratory study (n = 15) using the ELISA prototype to determine the clinical utility of TAP for early prediction of AP severity demonstrated that TAP is superior to CRP for the stratification of patients with mild and moderate AP. The sensitivity, specificity, negative predictive value (NPV) and positive predictive value (PPV) of TAP to predict the development of moderate AP at 48h after admission was 85.7%, 100.0%, 90.0% and 100%, respectively. The sensitivity, specificity, NPV and PPV of CRP to predict the development of moderate AP at 48h after admission was 85.7%, 69.2%, 90.0% and 60.0%, respectively. The lateral flow device also demonstrated the ability to distinguish between TAP positive and TAP negative clinical urine samples. In conclusion, TAP is a promising biomarker for the early prediction of severity in AP.