Background: Dipeptidyl peptidase-3 (DPP3) is a metallopeptidase which cleaves bioactive peptides, notably angiotensin II, and is involved in inflammation regulation. DPP3 has been proposed to be a myocardial depressant factor and to be involved in circulatory failure in acute illnesses, possibly due to angiotensin II cleavage. In this study, we evaluated the association between plasmatic DPP3 level and outcome (mortality and hemodynamic failure) in severely ill burn patients. Methods: In this biomarker analysis of a prospective cohort study, we included severely ill adult burn patients in two tertiary burn intensive care units. DPP3 was measured at admission (DPP3 admin) and 3 days after. The primary endpoint was 90-day mortality. Secondary endpoints were hemodynamic failure and acute kidney injury (AKI). Results: One hundred and eleven consecutive patients were enrolled. The median age was 48 (32.5-63) years, with a median total body surface area burned of 35% (25-53.5) and Abbreviated Burn Severity Index (ABSI) of 8 (7-11). Ninety-day mortality was 32%. The median DPP3 admin was significantly higher in non-survivors versus survivors (53.3 ng/mL [IQR 28.8-103.5] versus 27.1 ng/mL [IQR 19.4-38.9]; p < 0.0001). Patients with a sustained elevated DPP3 had an increased risk of death compared to patients with high DPP3 admin but decreased levels on day 3. Patients with circulatory failure had higher DPP3 admin (39.2 ng/mL [IQR 25.9-76.1] versus 28.4 ng/mL [IQR 19.8-39.6]; p = 0.001) as well as patients with AKI (49.7 ng/mL [IQR 30.3-87.3] versus 27.6 ng/mL [IQR 19.4-41.4]; p = 0.001). DPP3 admin added prognostic value on top of ABSI (added chi 2 12.2, p = 0.0005), Sequential Organ Failure Assessment (SOFA) score at admission (added chi 2 4.9, p = 0.0268), and plasma lactate at admission (added chi 2 6.9, p = 0.0086) to predict circulatory failure within the first 48 h.
Background
Although multiple individual immune parameters have been demonstrated to predict the occurrence of secondary infection after critical illness, significant questions remain with regards to the selection, timing and clinical utility of such immune monitoring tests.
Research question
As a sub-study of the REALISM study, the REALIST score was developed as a pragmatic approach to help clinicians better identify and stratify patients at high risk for secondary infection, using a simple set of relatively available and technically robust biomarkers.
Study design and methods
This is a sub-study of a single-centre prospective cohort study of immune profiling in critically ill adults admitted after severe trauma, major surgery or sepsis/septic shock. For the REALIST score, five immune parameters were pre-emptively selected based on their clinical applicability and technical robustness. Predictive power of different parameters and combinations of parameters was assessed. The main outcome of interest was the occurrence of secondary infection within 30 days.
Results
After excluding statistically redundant and poorly predictive parameters, three parameters remained in the REALIST score: mHLA-DR, percentage of immature (CD10− CD16−) neutrophils and serum IL-10 level. In the cohort of interest (n = 189), incidence of secondary infection at day 30 increased from 8% for patients with REALIST score of 0 to 46% in patients with a score of 3 abnormal parameters, measured ad D5–7. When adjusted for a priori identified clinical risk factors for secondary infection (SOFA score and invasive mechanical ventilation at D5–7), a higher REALIST score was independently associated with increased risk of secondary infection (42 events (22.2%), adjusted HR 3.22 (1.09–9.50), p = 0.034) and mortality (10 events (5.3%), p = 0.001).
Interpretation
We derived and presented the REALIST score, a simple and pragmatic stratification strategy which provides clinicians with a clear assessment of the immune status of their patients. This new tool could help optimize care of these individuals and could contribute in designing future trials of immune stimulation strategies.
Graphical Abstract
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