To study the prognostic value of the antiperinuclear factor (APF), determined by an indirect immunofluorescence test (IIF) and a recently developed anti-citrullinated cyclic peptide (CCP) ELISA, in combination with rheumatoid factor (RF) status, in early RA (< 1 year).
A total of 249 participants in a randomized trial of treatment strategies were divided into 4 groups according to their APF (or CCP) and RF status at baseline. Differences in disability, joint involvement and radiological damage over a 3-year period were analysed.
APF-IIF results differed from CCP-ELISA in 42 cases (17%); 38 of the 42 had a positive IIF and negative ELISA value. Disability after 3 years did not differ significantly between the RF and APF groups. APF- patients had significantly lower Thompson joint scores compared to APF+ patients (6 vs 24 for CCP-ELISA; 2 vs 24 for IIF). RF+APF+ patients exhibited more radiological damage compared to RF-APF- patients. RF+APF- and RF-APF+ patients had intermediate scores. Within the RF+ and RF- groups, APF+ was associated with more radiological damage and thus yielded prognostic information in addition to RF. In this respect, the results of ELISA and IIF were comparable. Thirty percent of the RF+APF+ patients had a radiological score higher than 45, compared to 13% of the RF+APF-, none of the RF-APF+, and 2% of RF-APF- patients (p < 0.001). In addition, more large joints were affected in APF+ than in APF- patients, while no difference was observed between RF+ and RF- patients.
APF has prognostic value in addition to RF for joint involvement and radiological damage in early RA. The CCP-ELISA technique for APF assessment may facilitate its use in clinical practice. However, the prognostic value of the two tests lies in their ability to predict mild disease. Reliable identification at baseline of individual patients with progressive disease is still not possible.