SAN FRANCISCO — An observational study of 395 patients with suspected early arthritis identified two factors that predicted a diagnosis of rheumatoid arthritis within a year's time.
Patients with swelling in a small joint of the hands and/or feet were six times more likely to be diagnosed with RA within a year than were patients whose swollen joints did not include those sites. A diagnosis was 39 times more likely in patients whose laboratory tests at baseline showed the presence of anti-cyclic citrullinated peptide antibodies, versus anti-CCP-negative patients, Dr. Maria D. Mjaavatten said at the annual meeting of the American College of Rheumatology.
The same factors also predicted (to a lesser degree) persistent arthritis and of subsequent use of disease-modifying antirheumatic drugs within a year, added Dr. Mjaavatten of the rheumatology department at Diakonhjemmet Hospital, Oslo.
Patients with small-joint arthritis were twice as likely to develop persistent arthritis and four times as likely to start a DMARD within a year compared with patients without small-joint involvement. Patients with anti-CCP positivity were five times more likely to develop persistent arthritis and nine times more likely to start a DMARD compared with anti-CCP-negative patients.
The results will help inform an ongoing effort by a joint European-American task force to define new diagnostic criteria for early rheumatoid arthritis, Dr. Mjaavatten said. Classification criteria from the ACR were developed in 1997 for established disease and are not as useful in early arthritis. The ACR and the European League Against Rheumatism convened the current task force.
The study enrolled adult patients with at least a 16-week history of one or more clinically swollen joints diagnosed as arthritis by rheumatologists at one of five Norwegian centers, and followed patients for at least a year. Although physicians were aware of the ACR diagnostic criteria for rheumatoid arthritis, diagnoses were not limited to patients who met those criteria, Dr. Mjaavatten noted.
The cohort represented approximately 70% of all patients enrolled. The other 30% were lost to follow-up before completing at least two follow-up assessments and were presumed to have nonpersistent arthritis. The study defined persistent arthritis as the presence of joint swelling on at least two out of three follow-up assessments during the first year.
The cohort was younger (mean age, 46) and included fewer women (57%) than a “typical” RA cohort, she noted. The mean arthritis duration at baseline was very short (30 days), with a duration of 10 days or less in a quarter of the patients.
During the year of follow-up, 18% of patients were diagnosed with rheumatoid arthritis and 26% had persistent arthritis. Among 301 patients whose charts had information on DMARDs, 36% started a DMARD during the year. Methotrexate was the dominant drug, used by 59% of patients on a DMARD. Another 9% used sulfasalazine, 28% took a combination of DMARDs or more than one DMARD during the year (including 13 patients who received biologics), and 4% used other DMARDs.
Some patients had more than one of the three main outcomes: an RA diagnosis, persistent arthritis, or DMARD use.
DMARDs were not started in about 5% of patients diagnosed with RA and about 15% of patients with persistent arthritis, Dr. Mjaavatten said. Around 16% of DMARD users had neither a diagnosis of RA nor persistent arthritis. At presentation, 38% of patients had single-joint arthritis, 33% had two to four swollen joints, and 29% had polyarthritis.
Dr. Mjaavatten reported no conflicts of interest relevant to this study.