Background The myeloperoxidase index (MPXI) is elevated in infection. We ascertained whether MPXI might be useful in differentiation of sepsis versus non-infectious systemic inflammatory response syndrome (SIRS) in emergency department (ED).

Methods After exclusion of patients with an age of <18 years, trauma, haematological disease and on anticancer chemotherapy, 444 consecutive cases with SIRS (sepsis: 224, 50.3%; and non-infectious SIRS: 220, 49.7%) diagnosed and treated at the ED of The Wonju Severance Christian Hospital from May 2012 to June 2012 were retrospectively reviewed.

Results Median MPXI was higher in sepsis versus non-infectious SIRS (0.1 (IQR: −3.1 to 2.5) vs −1.2 (−4.1 to 1.6), respectively, p=0.020). Median white cell count, neutrophil percentage, C reactive protein level and δ neutrophil index were also higher. However, MPXI resulted as not statistically useful for differential diagnostic parameter in analysis.

Conclusions MPXI is higher in sepsis than in non-infectious SIRS. However, there is currently no evidence that the MPXI adds any additional benefit to differentiate sepsis from non-infectious SIRS in the ED. Therefore, further study will be needed.