The association between phosphate level at admission and early mortality in acute pancreatitis

Background Abnormal phosphate levels are associated with adverse outcomes in critical illness. However, there is scarce evidence on phosphate’s impact on acute pancreatitis outcomes, and the few studies examining this subject are relatively small and show conflicting data. We sought to determine the association between phosphate level at admission and the clinical course and outcomes of acute pancreatitis. Methods In this retrospective single-center observational study, we included all adult patients admitted with a primary diagnosis of acute pancreatitis between January 2008 and June 2021. Phosphate levels at admission were classified as normal (2.8–4.5 mg/dl), low (below 2.8 mg/dl), or high (above 4.5 mg/dl). Results Out of 2308 cases, 1868 patients had documented phosphate levels at admission and were thus included in our final analysis. 1096 (59%) had normal phosphate levels, 686 (37%) had hypophosphatemia, and 86 (4.6%) had hyperphosphatemia on admission. 30-day mortality rates were 3.4%, 3.8%, and 19% in normal, low, and high phosphate levels, respectively. In univariate analysis, hyperphosphatemia was significantly associated with 30-day mortality, with an OR of 6.54 (95% CI 3.39–12.2, p < 0.001; AUC = 0.58). In a multivariate analysis adjusting for age, MAP, GFR, BUN, and pH, hyperphosphatemia remained a statistically significant independent predictor of early mortality (OR-2.93, 95% CI 1.28–6.51, p = 0.009). Hypophosphatemia was not significantly associated with 30-day mortality in univariate analysis, OR of 1.13 (95% CI 0.67–1.87, p = 0.6). Conclusion Hyperphosphatemia at admission was independently associated with increased 30-day mortality in patients with acute pancreatitis. Hypophosphatemia at admission was not significantly associated with 30-day mortality.