Association between fibrinogen-to-albumin ratio and prognosis in patients admitted to an intensive care unit

Background: The objective of this study was to investigate the usefulness of fibrinogen-to-albumin ratio (FAR) as a prognostic marker in patients admitted to an intensive care unit (ICU) compared with Sequential Organ Failure Assessment (SOFA) score, a widely used prognostic scoring system. Methods: Using a total of 18,562 consecutive adult patients who were admitted to ICU with available fibrinogen and albumin levels from June 2013 to May 2022. An inverse probability weighting (IPW) was used to control for selection bias and confounding factors. After estimating an optimal threshold, patients were divided accordingly, and 1-year mortality was compared. Results: One-year mortality was higher in 3rd tertile of FAR group compared with 1st and 2nd tertile of FAR groups (35.9%, 11.5%, and 13.3%, respectively). The threshold of FAR value was estimated to be 10.79 with the area under the curve of 0.68. According to the estimated threshold, patients were divided into a low FAR group (n = 12,533, 67.5%) and a high FAR group (n = 6,029, 32.5%). After IPW adjustment, the high FAR group showed significantly higher risk of 1-year compared with low FAR group (36.4% vs. 12.4%, adjust hazard ratio = 1.72; 95% confidence interval (CI): 1.59–1.86; P < 0.001). However, in the receiver-operating characteristic curve analysis associated with the prediction of 1-year mortality, there was no significant difference between the area under the curve of FAR on ICU admission (C-statistic: 0.684, 95% CI: 0.673 – 0.694) and that of SOFA score on ICU admission (C-statistic: 0.679, 95% CI: 0.669 – 0.688) (P = 0.532). Conclusions: In this study, FAR and SOFA score at ICU admission were associated with 1-year mortality in patients admitted to an ICU. Especially, FAR was easier to obtain in critically ill patients than SOFA score. Therefore, FAR is feasible and reliable in predicting long-term mortality in these patients.