The diagnostic value of streptococcal serology in early arthritis: a prospective cohort study

Objective. To evaluate the diagnostic value of streptococcal serology in adult early arthritis patients in discriminating between post‐streptococcal reactive arthritis (PSRA) and arthritis with other causes. Methods. The antistreptolysin‐O (ASO) and anti‐DNase B tests were performed at baseline in 366 consecutive, newly referred early arthritis patients. After 1 yr of follow‐up the patients were classified according to international classification criteria and were evaluated for the presence of persistent arthritis. The outcome measures were the predictive value of streptococcal serology for the diagnosis of PSRA and the ability of this serology to discriminate at the first visit between the self‐limiting and persistent forms of arthritis. Results. With a positive serological result, the probability of having PSRA increased from 2 to 9%, whereas the probabilities of having rheumatoid arthritis or undifferentiated arthritis continued to be high (23 and 29% ). The serological tests did not discriminate between the self‐limiting and persistent forms of arthritis. The major Jones criteria apart from arthritis were not observed. Conclusion. Streptococcal serology has no diagnostic value in adult early arthritis patients in whom major Jones criteria other than arthritis are not present.