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 nonprecipitated Concentration pg/mL precipitated Ratio precipitated : nonprecipitated Baseline concentration nonprecipitated/precipitated pg/mL IL-1β sensitivity: 10.5 pg/mL P1 369 272 0,737 0/0 P4 290,5 220 0,757 1.5/0 SF1 169 219 1,296 0/0 SF4 259 270 1,042 0/0 IL-4 sensitivity: 27 pg/mL P1 334 271 0,811 0/0 P4 309,8 245 0,791 0.2/0 SF1 336 292 0,869 0/0 SF4 337,6 355 1,052 3.4/0 IL-6 sensitivity: 11.5 pg/mL P1 368 290 0,788 0/0 P4 477,4 290 0,607 2.6/0 SF1 293 289 0,986 43/58 SF4 362 386 1,066 96/115 IL-8 sensitivity: 14.0 pg/mL P1 280 225 0,804 0/0 P4 355,8 275 0,773 9.2/0 SF1 306 296 0,967 54/29 SF4 387 398 1,028 88/42