Biomarkers in Patients With Flesh-eating Bacterial Infections

Necrotizing soft tissue infection (NSTI) is a complex, multi-factorial disease with diverse microbiological etiology and varying co-morbidities. The rapidly spreading infection may cause extensive soft tissue damage, limb loss, and multiple organ failure. The incidence of NSTIs has increased over the past years and the fatality rates are still high despite increased focus on these patients (20-30%). The extensive inflammatory response is thought to be a main course of death. However, it is unknown which biomarkers that are responsible for the deleterious effects and how these molecular mediators are modulated during the infection and treatment regimes. Thus, there is a need for novel insight into the immune system disturbances in order to improve outcome of NSTIs.

Location: Copenhagen University Hospital, Rigshospitalet, Denmark.

Design: Observational cohort study.

Cohort: NSTI patients in Denmark.

Controls: 50-100 Patients undergoing elective, orthopedic surgery at Rigshospitalet.

Biomarkers: The investigators will focus on three major groups of biomarkers: Acute-phase proteins, cytokines and vasoactive biomarkers.

Sample size calculations:

• Acute-phase proteins: The investigators expect a mean PTX3-concentration at admission at 120 nmol/L in patients without septic shock and a mean PTX3-concentration at 210 nmol/L in patients with septic shock. With an estimated standard deviation at 100 nmol/L, the inclusion of 52 patients will be able to detect a significant difference with a statistical power of 90% at a 5% significance level. Since the groups are unequal the investigators will need to include 82 patients (N'=52(1+4)^2/4*4).
• Cytokines: In a pilot study with seven NSTI patients, the investigators found a minimal clinically relevant difference in IL-6 concentration in NSTI patients with LRINEC < 6 and ≥ 6 to be 1050 pg/ml. With an estimated standard deviation at 2000 pg/ml, the inclusion of 114 patients will be able to detect a significant difference with a statistical power of 80% at a 5% significance level.
• Vasoactive proteins: The investigators expect a mean NOx-concentration at admission at 90 μmol/L in patients without septic shock and a mean NOx-concentration at 145 μmol/Lin patients with septic shock. With an estimated standard deviation at 70 μmol/L, the inclusion of 70 patients will be able to detect a significant difference with a statistical power of 90% at a 5% significance level. Since the groups are unequal the investigators will need to include 110 patients (N'=70(1+4)^2/4*4).

Data: Data will be handled according to the National Data Protection Agency. All original records (incl. consent forms and questionnaires) will be archived at trial site for 15 years. The National Data Protection Agency has approved the biobank (2007-58-0015, J. nr. 30-1282).

Ethics: The trial will adhere to the Helsinki Declaration and Danish law. The National Ethics Committee and the Regional Ethics Committee have approved the inclusion of the NSTI patients (CVK-1211709) and the control patients, including biomarker analyses (H-2-2014-071).

Biomarker analyses, data extraction and interpretation will be performed once the recruiting of participants has ended.

Inclusion criteria

for patients with NSTI:

• Necrotizing soft tissue infection based on surgical findings
• Age >18 years
• Admitted to/planned to be admitted to the ICU at Rigshospitalet and/or operated for NSTI at Rigshospitalet

Exclusion criteria

for patients with NSTI:

• Patients who at the operating theatre were categorized as non-NSTI patients

Inclusion criteria

for control patients:

• Patients undergoing elective orthopedic surgery (non-pathologic fractures, joint replacement surgery, back surgery) at Rigshospitalet
• Age >18 years

Exclusion criteria

for control patients:

• Patients with ongoing infections