Ueira et al. Arthritis Research  Therapy (2015) 17:Page 4 ofand were compared using the Student's t-test for unpaired comparisons using GraphPad Prism 6 software (La Jolla, CA, USA). Median values were also calculated in order to consider non-Gaussian distributions. As the mean and median values were generally coincident, the Mann-Whitney U test was not selected for statistical analysis. P Capivasertib Abstract(s)">PubMed ID:https://www.ncbi.nlm.nih.gov/pubmed/16989806 the healthy control responses; 2  of control population showed weak positive response to each peptide tested.ACPA blocking - inhibition of reactivity in the anti-CCP2 ELISAWe next sought to investigate if fibrinogen-derived peptides (citrullinated and unmodified versions) were able to compete with CCP2 for binding of patient-derived ACPA. Hence we performed an `ACPA competition' experiment, where purified human ACPA was pre-incubated with our fibrinogen peptides before being assayed on the antiCCP2 ELISA.aCit72 Cit65b481435531 2CitCit35856515Fig. 1 a. Percentage of responses among tested patients. Immune reactivity ( ) against the respective peptide in sera from CCP2-positive patients. Positive immune reactivity ( ) (dark grey) against each individual citrullinated fibrinogen peptide in sera from CCP2-positive patients; light gray represents negative im.