Table 2. Assay Linearity and Precision for the WHO Spiked Samples across All Participating Laboratoriesa.
| log10 SD |
detectable fold differenceb |
|||||||
|---|---|---|---|---|---|---|---|---|
| cytokine/assay | intra-assay | interlaboratory | intermatrix | intra-assay | interlaboratory | intermatrix | CV < 20% (%)c | linearity r2 |
| IL-1β | ||||||||
| BioSource | 0.04 (0.05) | 0.07 (0.19) | 0.15 (0.20) | 1.65 | 1.84 | 2.46 | 75.56 | 0.99 (0) |
| Endogen | 0.03 (0.03) | NAd | 0.07 (0.08) | 1.61 | NA | 1.84 | 96.67 | 0.98 (0.02) |
| Quantikine | 0.01 (0.04) | 0.13 (0.27) | 0.14 (0.26) | 1.5 | 2.35 | 2.39 | 86.67 | 1.00 (0.00) |
| QuantiGlo | 0.01 (0.02) | 0.08 (1.24) | 0.08 (1.17) | 1.45 | 1.9 | 1.89 | 98.33 | 1.00 (0.01) |
| Beadlyte Luminex | 0.02 (0.02) | 0.07 (0.29) | 0.37 (0.28) | 1.54 | 1.84 | 5.76 | 90 | 0.99 (0.01) |
| in-house Luminex | 0.03 (0.03) | 0.65 (0.08) | 0.62 (0.07) | 1.59 | 16.37 | 14.68 | 90 | 0.98 (0.03) |
| MSD Small Spot | 0.03 (0.03) | 0.05 (0.04) | 0.07 (0.05) | 1.56 | 1.68 | 1.88 | 96.67 | 0.99 (0.02) |
| IL-6 | ||||||||
| BioSource | 0.04 (0.05) | 0.30 (0.31) | 0.51 (0.18) | 1.64 | 4.4 | 9.49 | 76.67 | 0.99 (0.01) |
| Endogen | 0.03 (0.05) | 0.48 (0.58) | 0.66 (0.43) | 1.59 | 8.48 | 16.82 | 76.67 | 0.98 (0.04) |
| Quantikine | 0.02 (0.02) | 0.07 (0.05) | 0.21 (0.01) | 1.54 | 1.86 | 3.12 | 91.67 | 1.00 (0.00) |
| QuantiGlo | 0.03 (0.03) | 0.08 (0.1) | 0.28 (0.04) | 1.56 | 1.89 | 4.06 | 93.33 | 0.99 (0.01) |
| Beadlyte Luminex | 0.02 (0.03) | 0.41 (0.53) | 0.78 (0.33) | 1.54 | 6.5 | 26.07 | 96.67 | 0.79 (0.51) |
| in-house Luminex | 0.02 (0.03) | 0.40 (0.16) | 0.48 (0.18) | 1.54 | 6.31 | 8.62 | 90 | 1.00 (0.01) |
| MSD Small Spot | 0.03 (0.02) | 0.04 (0.01) | 0.21 (0.06) | 1.56 | 1.63 | 3.1 | 100 | 0.99 (0.01) |
a
Comparisons within (i) replicate samples (intra-assay), (ii) samples pooled from multiple laboratories (interlab), and (iii) samples pooled for the five different biological matrices (intermatrix). SD (log10 pg/mL) and linearity coefficient r2 are expressed as median (interquartile range).
b
The fold difference in cytokine concentration for which the assay would have 95% power to detect with P < 0.05.
c
The proportion (%) of measurements with an intra-assay CV <20%.
d
NA: not applicable (only one laboratory ran this assay).