Evidence-based diagnostics: adult septic arthritis

Area of Science:

• Orthopedics
• Infectious Diseases
• Emergency Medicine
• Diagnostic Accuracy

Background:

• Acutely swollen or painful joints are common emergency department (ED) complaints.
• Septic arthritis in adults presents a diagnostic challenge, requiring prompt differentiation of bacterial etiology to minimize morbidity and mortality.

Purpose of the Study:

• Systematic review of diagnostic characteristics for nongonococcal septic arthritis using history, physical examination, and bedside laboratory tests.
• Quantify test and treatment thresholds based on sensitivity, specificity, and best-evidence risks and benefits.

Main Methods:

• Systematic review of adult trials using PUBMED and EMBASE, including bibliography and hand searches.
• Meta-analysis of diagnostic test characteristics, calculating interval likelihood ratios (LRs).
• Development of an interactive spreadsheet to quantify test and treatment thresholds.

Main Results:

• Prevalence of nongonococcal septic arthritis in ED patients with a single acutely painful joint is approximately 27%.
• History, physical examination, and serum inflammatory markers (WBC, ESR, CRP) have limited diagnostic utility.
• Synovial white blood cell (sWBC) counts >50 × 10(9)/L significantly increase septic arthritis probability (infinite LR); synovial lactate and rapid PCR also show diagnostic potential.
• Test threshold for arthrocentesis is 5%, with a treatment threshold of 39% for sWBC >50 × 10(9)/L.

Conclusions:

• Recent joint surgery or overlying cellulitis are key historical/physical findings altering septic arthritis probability.
• Extreme sWBC values increase, but do not decrease, septic arthritis probability.
• Further ED-based trials are needed for clinical gestalt and novel synovial markers like lactate.