PTX3 and rheumatoid arthritis: Patients with seropositive RA in our study had significantly lower titres of anti-PTX3 antibodies compared with FM (0.120 ± 0.063 vs. 0.169 ± 0.032, P = 0.0048) and PsA (0.120 ± 0.063 vs. 0.171 ± 0.020, P = 0.0014) patients, while there were no significant differences between seropositive and seronegative RA, or seronegative RA and FM or PsA patients.