The pooled sensitivity, specificity, and positive likelihood ratio for anti-CCP antibody were 67%, 95%, and 12.46, and for IgM RF the values were 69%, 85%, and 4.86, respectively.11 Among several factors that could explain the discordant sensitivity and specificity between diverse studies, the frequency of a false positive test in non-RA controls deserves further consideration because the specificity is inversely related to the proportion of positive tests among controls. This evidence concerns the gene CD40LG and rheumatoid arthritis.