The utility of interleukin-6 compared to conventional sepsis biomarkers in pregnancy - A real-world cohort study.

OBJECTIVE

To assess the diagnostic performance of interleukin-6 (IL-6) versus in-use inflammatory markers (C-reactive protein [CRP], procalcitonin [PCT], neutrophil-lymphocyte ratio [NLR]) in maternal sepsis.

METHODS

This was a retrospective cohort study in a single Dublin maternity hospital. All maternity patients (conception to 6-weeks post-partum) in whom IL-6 was measured to investigate suspected sepsis in an 11-month period were included. Cases were categorized twice into physiological (normal, systemic inflammatory response syndrome, sepsis, septic shock) and etiological (bacterial, viral or no infection) categories. Biomarker performance was assessed by area under the receiver operating characteristic curves (AUC) and measures of diagnostic accuracy at optimal cut-offs. Serial sampling evaluated biomarker kinetics.

RESULTS

Seventy-two patients were included, 31.9 % had sepsis/septic shock, and 70.9 % had bacterial infection. Significant differences between categories were seen for both physiological and etiological axes for IL-6, for physiological categories alone for NLR, and for neither for PCT and CRP. IL-6 had an AUC of 0.78 for the primary physiological endpoint, significantly higher than CRP and PCT (p = 0.02), but not NLR (AUC 0.72, p = 0.47). The IL-6 AUC for the primary etiological endpoint was 0.94, higher than all other biomarkers (p < 0.001). IL-6 was highly sensitive (91.4 %) but poorly specific (55.1 %) for the physiological endpoint, while both were high in the diagnosis of bacterial infection (88.2 % and 90.5 %). On serial sampling, IL-6 fell rapidly between first and second sampling, while others initially rose further.

CONCLUSION

IL-6 exhibited significantly higher sensitivity compared to conventional sepsis biomarkers in detecting both bacterial infection and maternal sepsis.