A 72-year-old woman undergoes revision total hip replacement for aseptic loosening 12 years after the index surgery. Intraoperative cultures are sent and show no growth. Which serum marker, when persistently elevated preoperatively, most reliably distinguishes periprosthetic joint infection (PJI) from aseptic loosening before revision surgery?
- A Combined elevation of CRP (>10 mg/L) and ESR (>30 mm/hr) with synovial fluid WBC >3000 cells/µL ✓
- B Serum C-reactive protein (CRP) > 10 mg/L alone
- C Serum erythrocyte sedimentation rate (ESR) > 30 mm/hr alone
- D Serum interleukin-6 (IL-6) > 10 pg/mL alone
Correct answer: A. Combined elevation of CRP (>10 mg/L) and ESR (>30 mm/hr) with synovial fluid WBC >3000 cells/µL
Explanation
The 2018 MSIS/EBJIS definition of PJI requires a combination of criteria rather than a single serum marker. The combination of elevated CRP and ESR as major criteria, combined with synovial fluid WBC >3000 cells/µL (or >80% PMN), greatly increases diagnostic specificity for PJI over aseptic loosening. IL-6 >10 pg/mL has good sensitivity but is used as a minor criterion, not independently diagnostic. CRP or ESR alone have insufficient specificity for this critical preoperative distinction.
Reference: Maheshwari Essential Orthopaedics, 6th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.