. Serum IL-6 levels were measured by Quantikine High Sensitive Human IL-6 Immunoassay (R&D Systems, Inc., Minneapolis, MN), according to manufacturer's instructions. This method employs solid-phase ELISA techniques and has a detection limit of 0.016-0.110 pg/mL, with mean sensitivity of 0.039 pg/mL. The intra-assay coefficient of variations (CVs) were 6.9% to 7.4% over the range 0.43-5.53 pg/mL. Across the entire sample, IL-6 had a mean of 2.75 pg/mL (SD = 2.35). Because the distribution of IL-6 showed the typical right skew, we took the natural log to normalize the distribution. The correlation between the raw and transformed data was .91.
