ASL/ALT ratio as a triage marker for enteric fever in the emergency department

Abstract

Objective: Early differentiation of enteric (typhoid) fever from other febrile conditions has been difficult due to the non-specific clinical presentations and lack of substantiating laboratory clues. Transaminase alterations in enteric fever were thought to be non-specific and have not been investigated before in comparison with other febrile conditions with regards to their prevalence and the aspartate amino transferase/alanine amino transferase (AST/ALT) ratio. We sought to examine these parameters as triage markers for enteric fever. Methods: We retrospectively studied 106 patients with enteric fever diagnosed by positive blood culture. 112 febrile patients tested negative for malaria were taken as controls. The controls were matched to the test group with respect to demographic and baseline clinical features. Serum AST, ALT values on first visit to the emergency department was noted and AST/ALT ratio was determined. The values between the test and control groups were compared and the results were analyzed using appropriate statistical methods. Results: The mean AST and ALT levels were found to be significantly higher for enteric fever patients than the control group (109.91 U/L ± 76.07 vs. 29.93 U/L ± 16.74; p < 0.0001) and (83.60 U/L ± 68.04 vs. 32.12 U/L ± 21.79; p < 0.0001) respectively. The mean AST/ALT ratio was found to be higher among enteric fever patients compared to the control group (1.42 ± 0.60 vs.1.07 ± 0.44; p < 0.0001). AST/ALT ratio of ≥ 1 combined with AST of ≥ 40 U/L was found in 72.6% of enteric patients vs. 6.2% in the control group (p < 0.0001). Conclusions: As compared to other common febrile conditions, transaminase alterations in enteric fever seem to follow a specific pattern characterized by higher prevalence of mild elevations (mean levels < 3 fold the upper limit of normal) with a general trend of AST/ALT ratios ≥ 1. In the febrile adult, having an AST/ALT ratio of >1 combined with an AST level of >40 U/L, may provide a simple and cheap triage marker for blood cultures and closer observation especially in the emergency department.