Pre-analytical and biological variability in circulating interleukin 6 in healthy subjects and patients with rheumatoid arthritis

TY - JOUR

T1 - Pre-analytical and biological variability in circulating interleukin 6 in healthy subjects and patients with rheumatoid arthritis

AU - Knudsen, Lene S

AU - Christensen, Ib J

AU - Lottenburger, Tine

AU - Svendsen, Mads N

AU - Nielsen, Hans J

AU - Nielsen, Lone

AU - Hørslev-Petersen, Kim

AU - Jensen, Jens E B

AU - Kollerup, Gina

AU - Johansen, Julia S

PY - 2008

Y1 - 2008

N2 - Interleukin (IL)-6, a key player in the inflammatory response, may be a useful biomarker in rheumatoid arthritis (RA). The aim was to determine analytical variability, a reference interval in healthy subjects, and long- and short-term variation in serum and plasma IL-6 in healthy subjects and RA patients. An enzyme-linked immunosorbent assay from R&D was used for determination of serum and plasma IL-6. The IL-6 concentration did not depend on the type of anticoagulant used or the 3-h time delay between sampling and processing or repeated freeze-thaw cycles. The median plasma and serum IL-6 in 318 healthy subjects were 1.3 pg ml-1 (range 0.33-26) and 1.4 pg ml-1 (range 0.25-23), respectively. The median coefficient of variation in plasma IL-6 in 27 healthy subjects during 1 month, and repeated after 6 and 12 months were 27%, 31% and 26%, respectively. No significant long-term changes were observed in serum IL-6 over a 3-year period (14%, p=0.33). Exercise (cycling) increased serum IL-6 in healthy subjects but not in RA patients. In conclusion, circulating IL-6 is stable regarding sample handling and shows little variation over time. Changes in IL-6 concentrations >60% (2 times the biological variation) are likely to reflect changes in disease activity and not only pre-analytical or normal biological variability.

AB - Interleukin (IL)-6, a key player in the inflammatory response, may be a useful biomarker in rheumatoid arthritis (RA). The aim was to determine analytical variability, a reference interval in healthy subjects, and long- and short-term variation in serum and plasma IL-6 in healthy subjects and RA patients. An enzyme-linked immunosorbent assay from R&D was used for determination of serum and plasma IL-6. The IL-6 concentration did not depend on the type of anticoagulant used or the 3-h time delay between sampling and processing or repeated freeze-thaw cycles. The median plasma and serum IL-6 in 318 healthy subjects were 1.3 pg ml-1 (range 0.33-26) and 1.4 pg ml-1 (range 0.25-23), respectively. The median coefficient of variation in plasma IL-6 in 27 healthy subjects during 1 month, and repeated after 6 and 12 months were 27%, 31% and 26%, respectively. No significant long-term changes were observed in serum IL-6 over a 3-year period (14%, p=0.33). Exercise (cycling) increased serum IL-6 in healthy subjects but not in RA patients. In conclusion, circulating IL-6 is stable regarding sample handling and shows little variation over time. Changes in IL-6 concentrations >60% (2 times the biological variation) are likely to reflect changes in disease activity and not only pre-analytical or normal biological variability.

U2 - 10.1080/13547500701615017

DO - 10.1080/13547500701615017

M3 - Journal article

C2 - 17852075

SN - 1354-750X

VL - 13

SP - 59

EP - 78

JO - Biomarkers

JF - Biomarkers

IS - 1

ER -