The alpha-defensin can rule out septic arthritis in pediatric cases: a first case series study

Achieving a rapid diagnosis in suspected septic arthritis is challenging as a pathogen is only isolated in 50% of cases, and the necessary investigation takes time and delays treatment. The alpha-defensin lateral flow test (Synovasure) has been shown to effectively and rapidly diagnose prosthetic joint infection, with the benefit of early initiation of treatment. This study tests the hypothesis that the alpha-defensin can diagnose pediatric septic arthritis and differ nonseptic arthritis (NSA) in native joints. A retrospective cohort study analysis was carried out for patients presenting with joint pain and fever with a differential that included septic arthritis. The Synovasure alpha-defensin lateral flow test kit was used to detect alpha-defensin in synovial fluid aspirated from the symptomatic joint. Septic arthritis was defined as present when a causative bacteria was identified in either blood or synovial fluid culture, whereas NSA was recognized when a causative bacteria was not identified, drainage or antibiotic treatment was not implemented, and symptoms improved without joint destruction. Demographic data and culture results were compared between septic arthritis and NSA. Eighteen eligible cases were identified. Of these, six were defined as septic arthritis and 12 as NSA. There were no significant differences in age, body temperature, serum white blood cell count, and C-reactive protein. All cases with confirmed septic arthritis showed a positive alpha-defensin lateral flow test, whereas all of the NSA group showed a negative result. The Synovasure alpha-defensin lateral flow test may be a reliable investigation for rapidly distinguishing septic arthritis from NSA in children.