Canada: Neutrophil to lymphocyte ratio (NLR) can be a valuable triage test for the diagnosis of periprosthetic joint infection (PJI) after total joint arthroplasty (TJA) because it is cost-effective and readily available, a recent retrospective cohort study has shown.
"The study revealed significantly higher NLR levels in patients with PJI, particularly at the time of revision surgery compared to index surgery (6.89 vs. 2.85)," the researchers reported. "The mean NLR was markedly higher in patients undergoing revision for PJI (6.89) than in aseptic revisions (3.17)."
The findings were published online in the Journal of the American Academy of Orthopaedic Surgeons on March 15, 2024.
Periprosthetic joint infection following total joint arthroplasty is a severe complication posing notable clinical implications for patients and substantial economic burdens. The neutrophil-to-lymphocyte ratio is an emerging biomarker of inflammation, which may better predict PJI.
Against the above background, Thomas J. Wood, McMaster University, Hamilton, ON, Canada, and colleagues aimed to evaluate NLR changes in patients with confirmed PJI. They also compared NLR between an aseptic revision and a revision for PJI and established whether an NLR of 2.45 is an appropriate cutoff for predicting infection.
For this purpose, the researchers performed a retrospective review of patients who underwent revision TJA for PJI at a single center between 2005 and 2018 and compared it with an aseptic cohort who underwent aseptic revision TJA. NLR calculation was done from complete blood counts performed at index surgery and at the time of revision surgery. Receiver operating characteristic curves were analyzed, along with specificity, sensitivity, and positive and negative likelihood ratios. Eighty-nine patients were included in each cohort.
The study led to the following findings:
The mean NLR in patients who underwent revision for PJI was 2.85 (± 1.27) at the time of index surgery and 6.89 (± 6.64) at the time of revision surgery.
The mean NLR in patients undergoing revision for PJI (6.89) was significantly higher than aseptic revisions (3.17).
In conclusion, in patients who underwent revision surgery for periprosthetic joint infection, the neutrophil to lymphocyte ratio was markedly elevated at the time of revision compared with the time of index surgery.
"Because it is a readily available and cost-effective test, these findings suggest that NLR may be a useful triage test in PJI diagnosis," the researchers wrote.
Reference:
Nairn, Leah MD; Sivaratnam, Surabhi BHSc; Bali, Kamal MBBS, MSc, FRCSC; Wood, Thomas J. MD, MSc, FRCSC. Neutrophil to Lymphocyte Ratio as an Indicator of Periprosthetic Joint Infection: A Retrospective Cohort Study. Journal of the American Academy of Orthopaedic Surgeons 32(6):p 271-278, March 15, 2024. | DOI: 10.5435/JAAOS-D-23-00600