BACKGROUND: Iodine contrast agents (ICAs) are routinely used by radiologists to help guide intra-articular infiltrations. The aim of this study was to assess the in vitro effects of ICA on platelet function of human autologous Platelet-Rich Plasma (PRP). METHODS: One hundred thirty-seven consecutive patients with symptomatic femoral-patellar osteoarthritis were included. All were addressed to our institution for a fluoroscopy-guided intra-articular PRP infiltration of the pathological femoral-patellar joint. For each patient, 500 μl of PRP were sampled before intra-articular injection. First, PRP samples were mixed with 50 μl of 2 widely used ICA: Visipaque270® (Iodixanol, n = 58) and Iopamiron200® (Iopamidol, n = 69). PRP concentration ([PRP]) was measured at different delays of incubation (t = 0, 5, 10, 15, 20 and 30 min) enabling to calculate PRP ratio (defined as [PRP](t)/[PRP](0mn)) at each delay, for each mixture, in order to quantitatively assess the influence of ICA on PRP ratio. Second, the PRP samples of 10 additional patients were mixed with Visipaque270®, Visipaque270®, Iopamiron200® and phosphate buffer saline (PBS: control solution) in order to qualitatively assess the influence of ICA on platelet aggregation, using ADP, Collagen, Arachidonic acid and TRAP tests. The surface expression of human P-selectin, a marker of α-granule release, in the PRP + Visipaque270® and PRP + Iopamiron200® mixtures was finally compared. Repeated-measures ANOVA, classical 2-way ANOVA and Wilcoxon matched-pairs test were used to study the influence of ICA on PRP quality. RESULTS: There was no significant change in PRP ratio during the first 30mn of incubation (p = 0.991) whatever the ICA (p = 0.926). Whatever the aggregation test, there was no significant difference in the percentage of platelet aggregation between PRP + PBS, PRP + Visipaque270® and PRP + Iopamiron200® (p = 0.998), nor between PRP + PBS and PRP + Visipaque320® (p = 0.470). Finally, there was no significant difference in P-selectin expression between the PRP + Visipaque270® and PRP + Iopamiron200® mixtures (p = 0.500). CONCLUSION: At early delays of incubation, Visipaque® and Iopamiron®, which are two widely used ICA for intra-articular infiltrations, did not influence the in vitro platelet function nor the quality of PRP.< Réduire