Background The presence of rheumatoid factor (RF) and anti-citrullinated protein antibodies (ACPA) are classic risk factors used for the diagnosis and classification of rheumatoid arthritis (RA) patients. Seropositive patients are at higher risk of developing RA, although in early arthritis RF/ACPA may be within the range of normality.
Objectives To assess if the presence of basal Power Doppler (PD) signal in patients with negative baseline status for RF and ACPA may predict the risk of final diagnosis of RA according ACR criteria 1987, at 12 months of follow up.
Methods We included 48 patients remited to an early arthritis consulting with at least one of the following inclusion criteria: a) Swelling in 2 or more joints b) pain in MCPs, MTPs and/or the wrists c) morning stiffness of more than 30 minutes with <12 months of duration of the symptoms and negative for RF and ACPA, not previously treated with esteroides or DMARDs, without previous diagnose of RA or other inflammatory chronic articular disease. The presence of ultrasonographic Power Doppler (PD) signal on 28 joints (shoulders, elbows, wrists, MCPs, knees) and 44 joints (28 joints and in addition hips, tarsus, ankles and MTPs), was studied with an ultrasound equipment GE L5 by an expert rheumatologist. Presence of basal CRP and ESR and basal erosions (score ≥2 in at least one joint by modified Sharp method) for each patient were registered (only 44 patients with complete radiology sets available) by and independent trained radiologist. The patients who met criteria for RA according 1987 ACR during first 12 months of follow-up and did not have any exclusion criteria were classified as definite rheumatoid arhtritis. Statistical study: Chi-square, Fisher exact test, p univariant, Odds Ratio and Post-Test Probability calculation.
Results The presence of basal power doppler signal in ≥1 joints of 44 (PD44) at baseline shows statistically significant association with the RA diagnosis at 12 months by ACR 1987 classification criteria, with p=0.002, OR=19,46 (2,25–168,27) but the presence of at least one joint with power doppler signal of 28 joints (PD28) did not (p=0.111). Presence of basal radiographic erosions (RXERb) were associated to RA with p<0.0005 and OR 12,04 (2,87–50,45) as well as high CRP p=0.019, OR 4,20 (1,23–14,36). Elevated ESR was not associated to RA diagnosis. The presence of PD44 and RXERb together is greater in patients with final diagnose of RA, p<0.0005 OR 45,71 (5,08–410,92). The combined presence of PD28 and RXERb is also associated to RA diagnose p<0.0005, OR 31,11 (3,53–274,11). Post-test probability of RA (considering a given pretest probability of 10% for seronegative patients obtained in our study) was 61% (19,1–91,8) for PD44+RXERb, 58% (16,9–90,8) for PD28+RXERb and 30% (15–51.8%) for RXERb.
Conclusions The presence of at least one joint with power doppler signal on 44 joints (PD44) at baseline may help to predict progression to RA at 12 months according to ACR 1987 criteria in seronegative patients. Combined presence of PD44 or PD28 associated to basal radiographic erosions was able to select seronegative patients with higher risk of progression to RA at 12 months according to ACR 1987 criteria.
Disclosure of Interest None declared