This 2014 editorial by Parvizi presents the International Consensus Group's definition of periprosthetic joint infection (PJI). Developed at a 2013 Philadelphia meeting of 400 experts from 52 countries, it modifies the 2011 MSIS criteria by updating the minor criterion threshold and adding leukocyte esterase. Diagnostic cutoffs for synovial WBC, CRP, and PMN% are stratified by whether the infection is acute (<90 days) or chronic (>90 days).
Evaluating a painful arthroplasty without a standardized definition of infection means different clinicians and different studies are answering different questions. This consensus gave everyone the same rulebook.
When you tap a joint to rule out PJI, your synovial WBC cutoff depends entirely on timing. Use 10,000 cells/μL if symptoms started less than 90 days ago. Use 3,000 cells/μL if the presentation is chronic. Applying the wrong threshold to the wrong phase is one of the most common diagnostic errors in arthroplasty practice.
Do not order ESR in acute PJI. The consensus explicitly states it is unhelpful in that setting. Use CRP instead.
When the labs are all negative but you are still worried, particularly in a shoulder arthroplasty with indolent drainage or a knee that never quite recovered, remember the Propionibacterium acnes caveat. The criteria say "may be present without meeting these criteria." That sentence is load-bearing.
This 2014 editorial by Parvizi presents the International Consensus Group's definition of periprosthetic joint infection (PJI). Developed at a 2013 Philadelphia meeting of 400 experts from 52 countries, it modifies the 2011 MSIS criteria by updating the minor criterion threshold and adding leukocyte esterase. Diagnostic cutoffs for synovial WBC, CRP, and PMN% are stratified by whether the infection is acute (<90 days) or chronic (>90 days).
Evaluating a painful arthroplasty without a standardized definition of infection means different clinicians and different studies are answering different questions. This consensus gave everyone the same rulebook.
When you tap a joint to rule out PJI, your synovial WBC cutoff depends entirely on timing. Use 10,000 cells/μL if symptoms started less than 90 days ago. Use 3,000 cells/μL if the presentation is chronic. Applying the wrong threshold to the wrong phase is one of the most common diagnostic errors in arthroplasty practice.
Do not order ESR in acute PJI. The consensus explicitly states it is unhelpful in that setting. Use CRP instead.
When the labs are all negative but you are still worried, particularly in a shoulder arthroplasty with indolent drainage or a knee that never quite recovered, remember the Propionibacterium acnes caveat. The criteria say "may be present without meeting these criteria." That sentence is load-bearing.