The application of serum antibody to group A streptococcal polysaccharide in the diagnosis of atypical rheumatic fever / 中华风湿病学杂志

ABSTRACT

Objective To investigate the diagnostic value of antibody to group A streptococcal polysaccharide (ASP) in diagnosing atypical rheumatic fever (RF). Methods Fifty-seven cases including 33 atypical RF and 24 recurrent attack of RF with chronic rheumatic heart disease were included, and 57 patients suffered from other diseases were used as control. Nitrous acid extraction and molecular sieve chromatography was adopted to extract and purify the polysaccharide. The isolated portion of polysaccharide which possessed strongest antigenity was used to detect the level of serum ASP by enzyme-linked immunosorbent assay (ELISA). Erythrocyte sedimentation rate (ESR), antistreptolysin-O (ASO) and anti-deoxyribonuclease B (anti-DNase B) were tested with the same samples. Results The sensitivity and specificity of ASP in the diagnosis of atypical RF was 73.7% and 76.6%; while 47.4% and 46.4% for ESR respectively. As for the evaluation of streptococcal infection, the sensitivity and specificity of ASP, ASO and anti-Dnase B were 73.7%, 15.6%, 65.4% and 76.6%, 94.6%, 44.6%, respectively. ROC curve analysis and discriminant analysis were adopted to compare these laboratory measurements. The results demonstrated that ASP was superior to other methods. Conclusion ASP has a higher sensitivity together with a higher specificity than the other three methods for diagnosing the activity of RF and the infection of streptoccus. It should be a promising diagnostic test for atypical RF.