Pearson correlation coefficients of the "erythropoiesis index" (geometric mean of the linear expression values of the 67 probes in the erythropoiesis signature) and several cytokine protein levels. The "erythropoiesis index" was correlated with cytokine protein levels across all available samples. A correlation coefficient > 0.5 represents a large degree of correlation; a coefficient between 0.5 and 0.3 represents moderate correlation; a coefficient between 0.3 and 0.1 shows a small degree of correlation; and correlation < 0.1 represents a lack of correlation. (Open bar) Correlation across all samples, 16 normal controls, 24 enthesitis-related, six oligo, eight poly RF-, and eight systemic JIA. (Closed bar) Correlation in systemic JIA.