Assessment of Pancreatic Exocrine Insufficiency in Patients with Dyspepsia: Clinical Utility of the PEI-Test in Identifying and Monitoring Response to Enzyme Replacement Therapy

<b>Background and Objectives:</b> Functional dyspepsia (FD) often overlaps with Pancreatic Exocrine Insufficiency (PEI), leading to diagnostic delays. We aimed to evaluate the prevalence of PEI in patients presenting dyspeptic symptoms using the survey-based PEI test and to assess the clinical response to Pancreatic Enzyme Replacement Therapy (PERT). <b>Methods:</b> This study included 91 patients with PEI and 58 control subjects. PEI was evaluated using the PEI Patient-Reported Outcome (PRO) instrument and classified as mild, moderate, or severe according to the 18-item PEI test. Objective fat malabsorption was assessed by the acid steatocrit method using a gravimetric assay. Patients diagnosed with PEI received PERT, and treatment response was evaluated at follow-up with a repeat PEI test. <b>Results:</b> When the case and control groups were compared in terms of PEI scores, a statistically significant difference was found (<i>p</i> < 0.001). Fecal steatocrit value was found to be statistically significant with the PEI score (<i>p</i> = 0.017). No statistically significant difference was found between amylase, lipase, vitamin D, vitamin B12, and folic acid and the PEI score (<i>p</i> = 0.789, <i>p</i> = 0.299, <i>p</i> = 0.865, <i>p</i> = 0.153, and <i>p</i> = 0.855, respectively). A statistically significant difference was found between the pre-treatment PEI score and the post-treatment PEI score (<i>p</i> < 0.001). The mean pre-treatment PEI score was 1.52 ± 0.50, while the post-treatment PEI score was 0.42 ± 0.48. Approximately 72% reduction in PEI score was observed with treatment. <b>Conclusions:</b> The PEI test may represent a useful, non-invasive tool for identifying suspected pancreatic dysfunction in patients initially diagnosed with functional dyspepsia. Early integration of this tool into clinical practice can improve symptom control and prevent the misclassification of PEI as a purely functional disorder.