Two predictors of early arthritis identified

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 rheumatoid arthritis within a year than were patients whose swollen joints did not include those sites. A diagnosis of rheumatoid arthritis within a year was 39 times more likely in patients whose laboratory tests at baseline showed the presence of anti-cyclic citrullinated peptide (anti-CCP) antibodies compared with anti-CCP-negative patients, reported at the annual meeting of the American College of Rheumatology.

The same factors also were predictive (though to a lesser degree) of persistent arthritis and of subsequent use of disease-modifying antirheumatic drugs within a year, added the department of rheumatology at Diakonhjemmet Hospital, Oslo,

Patients with small-joint arthritis were twice 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. Classification criteria from the American College of Rheumatology (ACR) were developed in 1997 for established disease and are not as useful in early arthritis. The ACR and the European League Against Rheumatism (EULAR) convened the current task force.

“Rheumatoid arthritis is often undifferentiated. The disease course can be difficult to predict in the early stages,” but the newly identified predictors should help.

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 theumatoid arthritis, diagnoses were not limited to patients who met those criteria.

The cohort represented approximately 70 percent of all patients enrolled. The other 30 percent 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 years) and included fewer women (57 percent) than might be expected in a “typical” rheumatoid arthritis cohort, she noted. The mean arthritis duration at baseline was short (30 days), with a duration of 10 days or less in a quarter of the patients.

During the year of follow-up, 18 percent of patients were diagnosed with rheumatoid arthritis and 26 percent had persistent arthritis. Among 301 patients whose charts had information on DMARDs, 36 percent started a DMARD during the year. Methotrexate was the dominant drug, used by 59 percent of patients on a DMARD. Another 9 percent used sulfasalazine, 28 percent took a combination of DMARDs or more than one DMARD during the year (including 13 patients who received biologics), and 4 percent used other DMARDs.

Some patients had more than one of the three main outcomes: a rheumatoid arthritis diagnosis, persistent arthritis, or DMARD use. DMARDs were not started in approximately 5 percent of patients diagnosed with rheumatoid arthritis and about 15 percent of patients with persistent arthritis. Around 16 percent of DMARD users had neither a diagnosis of rheumatoid arthritis nor persistent arthritis.