PRTN3 and rheumatoid arthritis: An important recent pooled analysis of 2234 RA patients casts significant doubt on the concept that smoking specifically associates with ACPA alone as RA ever smokers (n = 1318) were found to have no significant association with single ACPA positivity, (OR 0.83, 95% CI 0.56–1.24), compared to ACPA and RF double seropositivity (OR 1.4, 95% CI 1.06–1.84) [6].