Last Updated: 2008-01-11 16:11:46 -0400 (Reuters Health)

NEW YORK (Reuters Health) – A study of patients with isolated monoarthritis indicates that they are not at risk for progression to rheumatoid arthritis, according to findings published in the December issue of the Journal of Rheumatology.

"Monoarthritis (MA) is inflammation in a single joint," Dr. Alain Saraux, of Hopital de la Cavale Blanche, Brest, France, and colleagues write. "Few prospective studies of outcomes in patients with early MA followed up since symptom onset are available."

The researchers studied a cohort of 270 patients with early arthritis, who were classified into three groups: those with a single episode of MA (MA, n = 27), those with MA and a past history of self-reported arthritis (MA + past, n = 23), and those with oligo- or polyarthritis (OA/PA, n = 220).

At 6-month intervals, the patients underwent evaluations that included a standardized examination, radiographs of the hands and feet, and standard laboratory tests for rheumatoid factors (RF), antiperinuclear factor (APF), antikeratin antibody (AKA), anticyclic citrullinated peptide antibody (anti-CCP), antinuclear antibodies (ANA), and HLA-AB-DR typing. The diagnosis was assessed by a hospital-based rheumatologist after a median follow-up of 30 months.

The investigators note that knee involvement was more common in the MA group than in the MA + past group (p < 0.03). Hand and metatarsophalangeal involvement was less common in the MA group.

"For both RF and anti-CCP, positive results were less common in the MA group than in the other two groups," Dr. Saraux and colleagues report. "No statistically significant differences were identified across the three groups for RF ELISA, AKA, HLA-DR4 haplotype, and positive HLA-B27 antigen."

None of the patients in the MA group were diagnosed with RA.

The MA group was less often prescribed disease modifying antirheumatic drugs (1/27) than the MA + past group (11/23) and the OA/PA group (108/220) (p < 0.0001).

"The MA group was clearly different from the other groups," the researchers conclude, "with a favorable outcome and no risk of progression to RA."

J Rheumatol 2007;34:2351-2357.

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