Moreover, even though the presence of rheumatoid factor (RF) and anti-citrullinated protein antibodies (ACPA) has been found to identify subjects at increased risk of progressing to RA [24], we elected not to limit entry to subjects that had developed these biomarkers, but rather to examine a broader group of subjects who had developed unexplained inflammatory arthritis within the past 3 months in order to determine whether the presence of these antibodies or even the classification of RA altered the likelihood of progressing to RA despite intense therapy. Here, PRTN3 is linked to rheumatoid arthritis.