Repeatability and variability of cytokine measurement in induced sputum supernatant
| Outcome | Visit 1 (N=15) | Visit 2 (N=15) | Visit 3 (N=12) | Correlation | SD (within) | SD (between) |
|---|---|---|---|---|---|---|
| α2-Macroglobulin (μg/mL) | 2.5 (0.3–23.9) | 3.2 (0.3–22.7) | 1.2 (0.3–72.1) | 0.93 (0.88–0.95) | 0.20 (0.07–0.37) | 0.61 (0.56–0.75) |
| CCL5 (pg/mL) | 17.8 (2.2–72.5) | 8.4 (2.2–82.9) | 7.3 (2.2–213.8) | 0.75 (0.75–0.95) | 0.43 (0.25–0.47) | 0.61 (0.60–0.69) |
| CXCL10 (pg/mL) | 764 (44–2 352) | 1002 (26–16 429) | 838 (45–16 632) | 0.69 (0.54–0.75) | 0.50 (0.49–0.70) | 0.68 (0.57–0.81) |
| CXCL11 (pg/mL) | 20.3 (0.1–319.1) | 16.5 (0.1–153.5) | 20 (0.1–62.6) | 0.49 (0.29–0.65) | 1.07 (0.81–1.66) | 0.93 (0.87–1.04) |
| CXCL9 (pg/mL) | 913 (56–7824) | 1006 (51–7591) | 657 (64–9964) | 0.83 (0.74–0.9) | 0.42 (0.38–0.54) | 0.68 (0.62–0.80) |
| ECP (ng/mL) | 87.3 (13.1–151.5) | 54.3 (17.7–181.2) | 65.9 (19.4–215.3) | 0.87 (0.75–0.89) | 0.17 (0.11–0.26) | 0.34 (0.32–0.36) |
| IL-1β (pg/mL) | 428 (68–4238) | 475 (62–3057) | 445 (71–1605) | 0.46 (0.27–0.77) | 0.57 (0.54–0.60) | 0.47 (0.41–0.55) |
| IL-6 (pg/mL) | 445 (82–1826) | 470 (62–4532) | 241 (71–4991) | 0.87 (0.68–0.92) | 0.27 (0.23–0.40) | 0.52 (0.38–0.55) |
| IL-8 (ng/mL) | 20 (5.8–83.7) | 19.3 (5.5–172.2) | 31.1 (6.6–117.2) | 0.59 (0.55–0.85) | 0.35 (0.25–0.35) | 0.40 (0.35–0.41) |
| MCP-1 (pg/mL) | 573 (144–1666) | 619 (210–4777) | 660 (225–4269) | 0.71 (0.69–0.72) | 0.29 (0.27–0.29) | 0.38 (0.28–0.40) |
| MIP-1β (pg/mL) | 278 (24–1693) | 249 (27–1984) | 254 (43–2151) | 0.74 (0.62–0.86) | 0.43 (0.37–0.50) | 0.53 (0.5–0.57) |
| NE (ng/mL) | 223 (62–668) | 274 (56–647) | 205 (44–3442) | 0.73 (0.6–0.76) | 0.24 (0.16–0.40) | 0.34 (0.32–0.50) |
Each grid of the table contains median (range) for corresponding outcome. The summaries in the columns 2–4 use untransformed values of the outcomes. The summaries in columns 5–7 use log-transformed (base 10) concentrations. The correlation value characterises a strength of association between repeated measures. The SD (within) is the estimated (within-patient) SD of the difference in outcomes observed for a patient at the different visits. The SD (between) is the estimated (between-patients) SD of the outcomes observed at particular visits. The summaries in columns 5–7 are calculated over three pairwise summaries (ie, (visit 1, visit 2), (visit 1, visit 3), (visit 2, visit 3)).
CCL, C-C motif chemokine ligand; COPD, chronic obstructive pulmonary disease; CXCL, C-X-C motif chemokine ligand; IL, interleukin; LLOQ, lower limit of quantification; NE, neutrophil elastase.