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Table 2 Assessment of sampling error in rheumatoid arthritis synovial biopsies

From: Quantitative biomarker analysis of synovial gene expression by real-time PCR

  % Coefficient of variation  
  Raw data (cell equivalents) Normalized (relative expression) Number of biopsies*
TNF-α 81.7 ± 16.5 56.2 ± 9.7 5.2 ± 1.6
IL-6 71.7 ± 17.2 62.7 ± 13.8 7.2 ± 1.8
MMP-1 59.4 ± 18.3 56.4 ± 14.8 6.4 ± 2.1
IL-1β 65.3 ± 15.1 46.9 ± 7.6 4.0 ± 0.64
  1. Data presented as mean ± standard error of the mean. Multiple biopsies were obtained from five rheumatoid arthritis synovial tissues and assayed for gene expression using the standard curve method. The coefficient of variation was calculated for each tissue and then the mean coefficient of variation was determined for each target gene. Data are presented as cell equivalents of expression and GAPDH normalized expression (relative expression) within each tissue. Note that for tumor necrosis factor alpha (TNF-α), matrix metalloproteinase 1 (MMP-1) and IL-1β normalization substantially reduced variation. *The number of biopsies required to limit the sample error to < 25%.