Systematic review reveals that synovial fluid analysis outperforms clinical exam in adults with acute joint pain, highlighting the necessity of urgent arthrocentesis.
Key Points
To evaluate the diagnostic accuracy and precision of clinical history, physical examination, and laboratory tests for diagnosing nongonococcal bacterial arthritis in adults.
Structured searches of PubMed and EMBASE (1966 to January 2007) for studies evaluating diagnostic accuracy of symptoms, physical exam findings, and lab tests for septic arthritis.
Three authors independently extracted data from 14 included studies comprising 6,242 patients, of whom 653 met the gold standard diagnostic criteria.
Joint pain (sensitivity, 85%; 95% CI, 78%-90%), joint swelling (sensitivity, 78%; 95% CI, 71%-85%), and fever (sensitivity, 57%; 95% CI, 52%-62%) were the only clinical findings present in more than half of patients.
Synovial fluid white blood cell (WBC) count provided the strongest diagnostic value, with likelihood ratios (LR) increasing across thresholds: <25,000/μL (LR, 0.32; 95% CI, 0.23-0.43), ≥25,000/μL (LR, 2.9; 95% CI, 2.5-3.4), >50,000/μL (LR, 7.7; 95% CI, 5.7-11.0), and >100,000/μL (LR, 28.0; 95% CI, 12.0-66.0).
Synovial fluid polymorphonuclear cell fractions of ≥90% elevated the likelihood of septic arthritis (LR, 3.4; 95% CI, 2.8-4.2), whereas counts <90% substantially lowered it (LR, 0.34; 95% CI, 0.25-0.47).