This systematic review and meta-analysis evaluated the diagnostic accuracy of two synovial fluid biomarkers — alpha-defensin immunoassay and leukocyte esterase strip test — for diagnosing periprosthetic joint infection (PJI). The reference standard was the MSIS diagnostic criteria. Eleven studies (2,321 patients for alpha-defensin; 545 for leukocyte esterase) were pooled to generate summary sensitivity, specificity, and AUC estimates.
Diagnosing PJI before revision surgery determines the entire treatment strategy — a missed infection converted to a one-stage revision becomes a catastrophic failure. Synovial fluid biomarkers give you a rapid, point-of-care answer that serum ESR and CRP cannot match in specificity.
Alpha-defensin's near-zero negative likelihood ratio means a negative result is highly reassuring when you are uncertain whether a painful arthroplasty is infected or mechanically failing. Leukocyte esterase offers comparable specificity (0.97) at a negligible cost, making it an attractive first-line screen — but its sensitivity of 0.81 with a confidence interval reaching as low as 0.49 means you should not rely on a negative strip test alone to exclude infection.
The practical framework: use leukocyte esterase as a rapid, inexpensive screen when you aspirate a joint; if the strip reads ++ the infection diagnosis is essentially confirmed. If the strip is negative but your clinical suspicion remains high, alpha-defensin provides a more definitive answer.
The important caveat from this paper: substantial heterogeneity (I² above 94% for both tests) and the small number of included studies mean these pooled estimates should be interpreted with caution. All studies originated from the USA, and alpha-defensin data came heavily from one research group, which limits generalizability.
This systematic review and meta-analysis evaluated the diagnostic accuracy of two synovial fluid biomarkers — alpha-defensin immunoassay and leukocyte esterase strip test — for diagnosing periprosthetic joint infection (PJI). The reference standard was the MSIS diagnostic criteria. Eleven studies (2,321 patients for alpha-defensin; 545 for leukocyte esterase) were pooled to generate summary sensitivity, specificity, and AUC estimates.
Diagnosing PJI before revision surgery determines the entire treatment strategy — a missed infection converted to a one-stage revision becomes a catastrophic failure. Synovial fluid biomarkers give you a rapid, point-of-care answer that serum ESR and CRP cannot match in specificity.
Alpha-defensin's near-zero negative likelihood ratio means a negative result is highly reassuring when you are uncertain whether a painful arthroplasty is infected or mechanically failing. Leukocyte esterase offers comparable specificity (0.97) at a negligible cost, making it an attractive first-line screen — but its sensitivity of 0.81 with a confidence interval reaching as low as 0.49 means you should not rely on a negative strip test alone to exclude infection.
The practical framework: use leukocyte esterase as a rapid, inexpensive screen when you aspirate a joint; if the strip reads ++ the infection diagnosis is essentially confirmed. If the strip is negative but your clinical suspicion remains high, alpha-defensin provides a more definitive answer.
The important caveat from this paper: substantial heterogeneity (I² above 94% for both tests) and the small number of included studies mean these pooled estimates should be interpreted with caution. All studies originated from the USA, and alpha-defensin data came heavily from one research group, which limits generalizability.