Table 3: Cytokine concentration in nonprecipitated and PEG-precipitated plasma samples with low RF (P1) and high RF (P4) and synovial fluid samples with low RF (SF1) and high RF (SF4) as well as sensitivity for the assay and ratio between concentrations in nonprecipitated and precipitated samples for IL-1β, IL-4, IL-6, and IL-8 (Spiked with 417 pg/mL. Recovery consistent and as given by manufacturers).

Concentration pg/mL nonprecipitatedConcentration pg/mL precipitatedRatio precipitated : nonprecipitatedBaseline concentration nonprecipitated/precipitated pg/mL

IL-1β sensitivity: 10.5 pg/mLP13692720,7370/0
P4290,52200,7571.5/0
SF11692191,2960/0
SF42592701,0420/0

IL-4 sensitivity: 27 pg/mLP13342710,8110/0
P4309,82450,7910.2/0
SF13362920,8690/0
SF4337,63551,0523.4/0

IL-6 sensitivity: 11.5 pg/mLP13682900,7880/0
P4477,42900,6072.6/0
SF12932890,98643/58
SF43623861,06696/115

IL-8 sensitivity: 14.0 pg/mLP12802250,8040/0
P4355,82750,7739.2/0
SF13062960,96754/29
SF43873981,02888/42