237 Short-term effect of low-dose colchicine on biomarkers a central core laboratory. Hs-CRP was measured using a research hs-CRP Elisa kit (Hycult Biotech #HK369, Uden, the Netherlands). The lower detection limit of this assay was 0.4ng/L and the inter- and intra-assay coefficients of variation were <6.9% and <6.3% respectively. IL-6 levels were measured by highly sensitive human IL-6 immunoassay (R&D Systems #D6050, Minneapolis, MN, USA) for which intra-assay and inter-assay coefficients of variation ranged from 4.2% to 6.4%. This assay had a sensitivity of 0.7 pg/mL. The hematology parameters were determined with the XN9000 of Sysmex (Sysmex, Kobe, Japan). The serum LDL cholesterol was determined with the thirdgeneration homogeneous enzymatic colorimetric assay, the serum creatinine with the second-generation enzymatic assay. These analyses were carried out in a routine setting under ISO15189 compliance. Statistical analysis We estimated that using a sample size of 130 subjects would provide 80% power to detect a mean of the differences of -1 mg/dl in hs-CRP concentration, assuming a standard deviation of 4 mg/dl. Due to the expected non-normal distribution of differences, the minimal number of participants was extended with 15% to increase discriminative power in non-parametric testing.20 Central tendencies and distribution of continuous parameters were displayed using mean or median with standard deviation or 25th and 75th percentile in case of normally and non-normally distributed variables respectively. Categorical variables were presented as proportions. Paired differences of parameters were evaluated and provided using the mean or median of the differences and the corresponding 95% confidence interval (CI). Standard errors and confidence intervals for medians in non-parametric distributions were computed using biascorrected and accelerated bootstrapping. A Hodges–Lehmann estimator was used to provide a pseudo-median and confidence interval of the differences between non-parametric distributions. Formal hypothesis testing was done using a paired sample T–test for normally distributed differences and the Wilcoxon Signed Rank Test with continuity correction for non-normally distributed differences. The linear relationship of two continuous parameters was calculated using the Spearman's rank correlation coefficient.
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