PRTN3 and periodontitis: When dividing EIRA subjects into different age groups, prevalence of periodontitis—as determined based on the diagnostic code for periodontitis—was shown to increase significantly (p < 0.01) by age, in line with previous reports [51], in both RA and controls (Fig 2A) irrespective of ACPA-status or gender (Fig 2B, 2C and 2D).