Analytical precision of selected IMPACT assays and comparison with standard single assays. (a) Analytical precision. Intra-assay coefficients of variance (CV) were generated by performing 21 replicate measurements of each of nine markers in one sample within one run on the IMPACT platform. Inter-assay CVs were calculated based on results from 5 to 15 independent runs of the same sample on the IMPACT platform. The range of the CV for each marker corresponds to that of three independent pools of sample analyzed at low, medium, and high concentrations. (b) Correlation of values obtained with the Roche IMPACT platform with those obtained with the standard Roche Tina Quant (latex aggregation) assay. IgM autoantibody reactivity to rheumatoid factor (IgM-RF) in 1,312 RA serum samples was measured with the IMPACT platform and with Tina Quant assay. C-reactive protein (CRP) levels in 1,198 RA serum samples were measured with the IMPACT platform and with Tina Quant assay. Linear regression was used to determine the correlation between the multiplex chip assay (IMPACT) and the standard single assay (Tina Quant). IL-6, interleukin-6; MMP3, matrix metalloproteinase 3; SAA, serum amyloid A.