Imperial Collage Healthcare

Filter by A-Z

Interleukin‑6 (IL‑6)

Test Background
Interleukin‑6 (IL‑6) is a pleiotropic cytokine with a wide range of functions including induction of the acute phase response and regulation of innate and adaptive immunity. IL‑6 production is rapidly induced in the course of acute inflammatory reactions associated with injury, trauma, stress, infection, brain death and neoplasia

Clinical Indications

IL‑6 concentrations in trauma patients may predict later complications from additional surgical stress or indicate missed injuries or complications. Sequential measurements of IL‑6 in patients admitted to the intensive care unit (ICU) can be useful in evaluating the severity of systemic inflammatory response syndrome (SIRS), sepsis and septic shock and as a prognostic marker. IL‑6 is also useful as an early marker for the detection of neonatal sepsis. In addition, IL‑6 plays a role in chronic inflammation e.g. rheumatoid arthritis.

In patients with COVID-19 due to SARS CoV-2 infection, increased concentrations of IL-6 have been shown to correlate with severity of disease, risk of respiratory failure and development of SIRS though specific cut-offs have not yet been established.

Reference Range

<7 pg/mL

Reference range derived from kit manufacturer; 95th centile of apparently healthy individuals (n=817).

Measurements performed on samples from 281 ICU patients with either a known or suspected infection. The patients were classified into categories based on the ACCP/SCCM (American College of Chest Physicians / Society of Critical Care Medicine) consensus criteria: SIRS, sepsis, severe sepsis and septic shock. The median IL‑6 values of the patients with SIRS (n = 94) or sepsis (n = 65), severe sepsis (n = 60) or septic shock (n = 62) were as follows:



Median IL-6 concentration (pg/mL)

Range of IL-6 concentrations (pg/mL)



<1.5 – 2,062



6.5 – 3,122

Severe sepsis


15.2 – 39,121

Septic shock


8.6 – 171,257


(Data provided by kit manufacturer)

Sample Required
Serum preferred (gold top or red top). Lithium heparin (green top) and EDTA (purple top) plasma also acceptable.

Sample Volume
0.5 mL


Samples are stable for 5 hours at room temperature (20-25oC), 24 hours at 2-8oC, three months at -20oC.

Referral samples should be separated, frozen and transported on dry ice.

Turnaround Time

2 days

(Test available Monday – Friday only)


Roche Elecsys method (cobas e411).

Falsely low results may be obtained for this test due to biotin interference. Samples should not be taken from patients receiving therapy with high biotin doses (>5 mg/day) until at least 8 hours (ideally 2 days) following the last biotin administration.

Select a test from the list to view more details.