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Table 3 Rank correlation coefficients and the 95% limits of agreement between measurements of six inflammatory markers in induced and spontaneous sputum samples

From: Comparison of inflammatory markers in induced and spontaneous sputum in a cohort of COPD patients

  Correlation coefficient* Bland & Altmans 95% limit of agreement
   Lower Upper
IL-6 (pg/ml) 0.729 0.12 6.35
IL-8 (pg/ml) 0.695 0.12 5.59
IP-10 (pg/ml) 0.833 0.08 13.7
TNF-α (pg/ml) 0.600 0.11 5.53
IL-18 (pg/ml) 0.583 0.09 29.99
MIG (pg/ml) 0.754 0.10 17.24
  1. *Spearman’s rank correlation test.
  2. ±2 SD of the mean difference between the two measurements.