Abstract Background/Aims Prompt diagnosis of septic arthritis in acute native hot joint presentations is essential to guide management. Patients are frequently admitted and treated with antibiotics whilst awaiting synovial fluid (SF) culture results, which may take 48hours. A rapid test to exclude septic arthritis would reduce unnecessary antibiotics and hospital admissions. Aim: To evaluate the utility of SF and serum tests in differentiating septic from non-septic causes of acute hot joints. Methods We performed a systematic literature review of diagnostic testing for diagnosis/exclusion of septic arthritis in acute hot joints. Medline, Scopus and Cochrane Library were searched by two researchers. Search strategy included MeSH terms for: causes of a hot or swollen joint or effusion; diagnostic marker or test; SF or serum. Inclusion criteria were: ≥1 serum or SF test(s) to differentiate septic from non-septic causes of acute hot native joints, compared with clinical assessment and SF microscopy and culture. English-language articles only were included, without date restriction. In addition to patient demographics, diagnoses and comparator diagnoses, the following was recorded for each test and threshold (where applicable): sensitivity, specificity, positive/negative predictive values and likelihood ratios, of septic arthritis. For directly comparable tests (i.e. identical fluid, test and threshold), bivariate random-effects meta-analysis was used to pool sensitivity, specificity and areas under curve (AUC). Results 8,443 articles were identified, with 54 eligible for inclusion. Information on 28 distinct markers in SF and serum, differentiating septic from non-septic joints, was extracted. Most markers had been tested at multiple potential diagnostic thresholds, yielding a total of 27 serum markers and 156 SF markers. Due to heterogeneity of study design, outcomes and diagnostic thresholds, meta-analysis was possible for only eight tests differentiating septic from non-septic joints (Table 1). P103 Table 1:Sensitivity, specificity and AUCs for SF tests included in the meta-analysis.Synovial fluid testNumber of articles in meta- analysisSensitivity (95% CI)Specificity (95% CI)AUCGlucose (40mg/dL)20.59 (0.48, 0.69)0.86 (0.75, 0.92)0.593Lactate (≥5mmol/L)20.56 (0.32, 0.78)0.77 (0.67, 0.84)0.768Lactate (≥10mmol/L)20.36 (0.22, 0.53)0.99 (0.96, 1.00)0.852Leukocyte esterase ( ++ or +++)40.94 (0.70, 0.99)0.74 (0.67, 0.81)0.784Polymorphonuclear cells (>90%)20.69 (0.41, 0.88)0.65 (0.53, 0.75)0.665Pro-calcitonin (0.5μg/L)20.67 (0.26, 0.92)0.93 (0.84, 0.97)0.931Tumour necrosis factor α (36pg/mL)20.86 (0.49, 0.97)0.88 (0.54, 0.98)0.931White blood cells (50,000/mm3)50.56 (0.42, 0.69)0.90 (0.87, 0.92)0.895A test was eligible for meta-analysis if > 1 study used the same marker, threshold and fluid. Studies testing markers at other thresholds and/or in serum were not eligible for meta-analysis if not replicated in a second study. Conclusion Our review demonstrates many single tests with some evidence for diagnostic utility but individually with suboptimal accuracy, for exclusion of native joint infection. A far greater number of SF than serum tests were identified. A combination of several tests +/- stratification score is potentially required to optimise diagnostic accuracy. Further work is therefore indicated on the use of rapid and cost-effective biomarkers for the acute hot joint. Disclosure M. Dey: None. M. Al-Attar: None. L. Peruffo: None. S.S. Zhao: None. S. Duffield: None. N.J. Goodson: None.