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Evidence-based Diagnostics: Adult Septic Arthritis Full Text
Academic Emergency Medicine, 08/22/2011
Evidence Based Medicine
Carpenter CR et al. – Recent joint surgery or cellulitis overlying a prosthetic hip or knee were the only findings on history or physical examination that significantly alter the probability of nongonococcal septic arthritis. Extreme values of sWBC (>50 × 109/L) can increase, but not decrease, the probability of septic arthritis. Future ED–based diagnostic trials are needed to evaluate the role of clinical gestalt and the efficacy of nontraditional synovial markers such as lactate.
Methods- Two electronic search engines (PUBMED and EMBASE) were used in conjunction with a selected bibliography and scientific hand search.
- Inclusion criteria included adult trials of patients presenting with monoarticular complaints if they reported sufficient detail to reconstruct partial or complete 2 × 2 contingency tables for experimental diagnostic test characteristics using an acceptable criterion standard.
- Evidence was rated by two investigators using the Quality Assessment Tool for Diagnostic Accuracy Studies (QUADAS)
- When more than one similarly designed trial existed for a diagnostic test, meta–analysis was conducted using a random effects model.
- Interval likelihood ratios (LRs) were computed when possible.
- To illustrate one method to quantify theoretical points in the probability of disease whereby clinicians might cease testing altogether and either withhold treatment (test threshold) or initiate definitive therapy in lieu of further diagnostics (treatment threshold), an interactive spreadsheet was designed and sample calculations were provided based on research estimates of diagnostic accuracy, diagnostic risk, and therapeutic risk/benefits.
- The prevalence of nongonococcal septic arthritis in ED patients with a single acutely painful joint is approximately 27% (95% confidence interval [CI]=17% to 38%).
- With the exception of joint surgery (positive likelihood ratio [+LR]=6.9) or skin infection overlying a prosthetic joint (+LR=15.0), history, physical examination, and serum tests do not significantly alter posttest probability.
- Serum inflammatory markers such as white blood cell (WBC) counts, erythrocyte sedimentation rate (ESR), and C–reactive protein (CRP) are not useful acutely.
- The interval LR for synovial white blood cell (sWBC) counts of 0 × 109–25 × 109/L was 0.33; for 25 × 109–50 × 109/L, 1.06; for 50 × 109–100 × 109/L, 3.59; and exceeding 100 × 109/L, infinity.
- Synovial lactate may be useful to rule in or rule out the diagnosis of septic arthritis with a +LR ranging from 2.4 to infinity, and negative likelihood ratio (–LR) ranging from 0 to 0.46.
- Rapid polymerase chain reaction (PCR) of synovial fluid may identify the causative organism within 3 hours.
- Based on 56% sensitivity and 90% specificity for sWBC counts of >50 × 109/L in conjunction with best–evidence estimates for diagnosis–related risk and treatment–related risk/benefit, the arthrocentesis test threshold is 5%, with a treatment threshold of 39%.