Red cell distribution width and red cell distribution width to total serum calcium ratio as major predictors of severity and mortality in acute pancreatitis

BACKGROUND: Acute pancreatitis (AP) is associated with considerable morbidity and mortality. Current severity scores include multiple variables and some of them are only complete within 48 h of admission. Red cell distribution width (RDW) is a simple and routine parameter that seems to be related to inflammatory status. Our aims were to evaluate the diagnostic value of RDW in severity and mortality of AP comparing with other prognostic scoring systems. METHODS: Retrospective case-control study of a total of 312 patients with AP admitted between 2014 and 2016. Patients with severe AP (cases) were compared with patients with mild AP (controls) in the 1:1 proportion. Additionally, a comparison between survivor and nonsurvivor AP patients was performed. Diagnosis and severity of AP were defined according to the revised Atlanta classification 2012. Variables evaluated included demographics, comorbidities, hospital stay, laboratorial parameters, arterial blood gas analysis, prognostic scores within 24 h of admission (Ranson, BISAP and Modified Marshall) and mortality. RESULTS: Included 91 cases of severe AP, most males (58.2% vs 51.6%; p = 0.228) with mean age of 64.8 ± 16.3 years (vs 67.9 ± 13.7; p = 0.239). RDW(0h) was higher in patients with severe AP (14.6 ± 1.3 vs 12.7 ± 0.5; p < 0.001), as well as RDW(0h)-to-serum calcium ratio (1.8 ± 0.3 vs 1.3 ± 0.1; p < 0.001). After multivariate and ROC curve analysis, RDW(0h) (AUROC: 0.960; p < 0.001) and RDW(0h)-to-serum calcium ratio (AUROC: 0.973; p < 0.001) were the major predictors of severe AP for a cut-off value of 13.0 (S: 92.7%; Sp: 84.3%) and 1.4 (S: 96.3%; Sp: 84.3%), respectively. These factors were superior to prognostic scores, such as Ranson (AUROC: 0.777; p < 0.001; cut-off: 3.0), BISAP (AUROC: 0.732; p < 0.001; cut-off: 2.0) and Modified Marshall (AUROC: 0.756; p < 0.001; cut-off: 1.0). The mortality rate was 8.8% (16/182), all cases associated with severe AP (17.6%; 16/91). RDW(0h) and RDW(0h)-to-serum calcium ratio were higher in nonsurvivor AP patients (15.3 ± 1.4 vs 13.5 ± 1.3; p < 0.001 and 2.0 ± 0.3 vs 1.6 ± 0.3; p < 0.001, respectively). In multivariate and ROC curve analysis, RDW(0h) (AUROC: 0.842; p < 0.001; cut-off: 14.0), RDW(24h) (AUROC: 0.848; p < 0.001; cut-off: 13.8) and RDW(0h)-to-serum calcium ratio (AUROC: 0.820; p < 0.001; cut-off: 1.7) were independent predictors for AP mortality, superior to conventional prognostic scoring systems Ranson (AUROC: 0.640; p = 0.003; cut-off:3.0), BISAP (AUROC: 0.693; p = 0.017; cut-off: 2.0) and Modified Marshall (AUROC: 0.806; p < 0.001; cut-off:1.0). CONCLUSIONS: RDW is a simple routine parameter, available at admission. This AP cohort showed that RDW(0h) > 13.0 and RDW(0h)-to-total serum calcium ratio > 1.4 were excellent predictors for severity and RDW(0h) > 14.0 and RDW(0h)-to-total serum calcium ratio > 1.7 were very-good predictors for mortality, being superior to conventional prognostic scoring systems.