Diagnostic evaluation of classification criteria for rheumatoid arthritis and reactive arthritis in an early synovitis outpatient clinic

OBJECTIVE: To evaluate the diagnostic performance of classification criteria for rheumatoid arthritis (RA) and reactive arthritis (ReA) in an early synovitis outpatient clinic. METHODS: In a prospective two year survey consecutive patients with early synovitis of less than one year duration were documented using a standardised registry and were classified after an expert diagnosis. Of a total of 320 patients 39 (19%) were diagnosed as having RA, 24 (11%) patients had ReA, 117 (54%) patients did not have an unequivocal diagnosis, and were considered as undifferentiated arthritis. RESULTS: The retrospective application of the revised 1987 ACR criteria for the classification of RA in this data set revealed a sensitivity of 90% and a specificity of 90%. The positive predictive value was 0.67, the negative predictive value 0.98. Similarly, the criteria for ReA of the French Society of Rheumatology (FSR) showed a sensitivity of 80% and a specificity of 90% with a positive predictive value of 0.55 and a negative predictive value of 0.97. Both criteria sets had a satisfying likelihood ratio of 9 and 10, respectively. CONCLUSION: Both the 1987 ACR criteria for RA and the criteria of the FSR for ReA have a reasonable diagnostic validity in patients with early synovitis, including a large portion of undifferentiated arthritis.