Interleukin 6 (IL6) Test

Description

USEFUL FOR 

Evaluation of patients with suspected systemic inflammation associated with infections, autoimmunity, and cancers

CLINICAL INFORMATION 

Interleukin-6 (IL-6) is an important pro-inflammatory cytokine, which plays critical roles in both innate and adaptive immunity.(1,2) IL-6 is produced by a variety of different cell types, including macrophages, endothelial cells, and T cells. Its production can be initiated in response to microbial invasion or other cytokines, such as tumor necrosis factor alpha (TNF-alpha) and IL-1 beta. As part of the innate immune system, IL-6 acts on hepatocytes to induce expression of C-reactive protein, fibrinogen, and serum amyloid A, also known as the acute phase reactants. IL-6 also plays a key role in activating antibody-producing B cells to proliferate, leading to an enhanced antibody response.(1)

Under normal conditions, IL-6 plays an important role in cellular homeostasis. However, during inflammatory conditions, the concentration of IL-6 increases in several folds, highlighting its clinical relevance as a major alarm signal in humans in response to infections (sepsis/septicemia), inflammation, autoimmunity, and cancer.(2-4) Increased concentrations of IL-6 have been reported in localized (prosthetic joint infections [PJI], periodontitis), and systemic (eg, sepsis, coronavirus 2019 [COVID-19]) infections, autoimmune conditions (eg, rheumatoid arthritis (RA), systemic lupus erythematosus, ankylosing spondylitis, and inflammatory bowel disease), and cancers.(4-8) Thus, IL-6 serum levels have evaluated, and reported to predict severity and response to IL-6 targeted therapies in PJI,(4) sepsis,(5) COVID-19,(6) and RA.(7-8) Overall, IL-6 cytokine is nonspecific biomarker of systemic inflammation that may have relevance in clinical decision making in the appropriate context.

REFERENCE VALUES 

< or =1.8 pg/mL

INTERPRETATION 

ELEVATED CONCENTRATIONS OF INTERLEUKIN-6 (IL-6) MAY INDICATE AN ONGOING INFLAMMATORY RESPONSE.

CAUTIONS 

Interleukin-6 (IL-6) is a nonspecific marker associated with an inflammatory response and is not diagnostic for any specific disease or disease process. Elevated concentrations of IL-6 must be interpreted within the clinical context of the patient.

Normal concentrations of IL-6 do not exclude the possibility of an ongoing inflammatory process.

IL-6 HAS LIMITED STABILITY. FOLLOWING CENTRIFUGATION, PLASMA MUST BE EITHER IMMEDIATELY FROZEN OR REFRIGERATED. SPECIMENS CAN BE STORED AT REFRIGERATED TEMPERATURES FOR ONLY 24 HOURS, AFTER WHICH TIME THEY MUST BE FROZEN. STORAGE OF PLASMA FOR ANY LENGTH OF TIME AT AMBIENT TEMPERATURE IS NOT ACCEPTABLE.