223 Joint Aspirations for Suspected Native Septic Arthritis: A Retrospective Audit of the Diagnostic Accuracy of Aspirations and Clinical Factors Associated with a Diagnosis of Septic Arthritis

Abstract

Abstract Aim This study aimed to determine the diagnostic accuracy of native joint aspirations for adult septic arthritis (SA), and to determine clinical factors associated with a positive diagnosis of SA. Method Retrospective review of adult patients (≥16yrs) undergoing a major joint aspiration at a single centre over a year period (2019) were identified. Patient demographics, clinical and biochemical data, joint aspiration details, post-aspiration diagnosis, management and patient outcomes were recorded. Culture negative SA was defined as Newman's Criteria C or D. Results There were 161 native joint aspirations identified. The rate of positive diagnosis of SA was 13.0%, (n=21), with 16 (9.9%) culture positive SA and five (3.1%) culture negative SA. The presence of organisms on gram stain, high synovial white cell count (WCC), history of fever, intravenous drug use (IVDU) and previous SA diagnosis were associated with a diagnosis of SA (all p<0.05). A history of crystal arthropathy made the diagnosis of SA less likely (p=0.025). C-reactive protein (CRP) was not statistically different in the SA and non-SA groups (Area Under Curve of ROC=0.63, p=0.55). Conclusion Joint aspiration is still the preferred diagnostic test when it comes to accurately diagnosing native joint SA. However, while synovial culture and gram stain are pending, a high index of suspicion for SA can be based on a combination of patient's presenting symptoms (history of fever), previous SA or IVDU, and a high synovial WCC. These factors can aid the decision as to whether an emergency surgical washout of the joint is indicated.