Total Lymphocyte Count Fails as a Predictor of Acute Periprosthetic Joint Infection for Total Hip or Knee Arthroplasty.

Abstract

Malnutrition is associated with an increased risk of periprosthetic joint infection (PJI) following total joint arthroplasty (TJA). Total lymphocyte count (TLC) has been employed as a measure of nutritional status, with a value of less than 1,500 cells/μL often used as a marker of malnutrition. This study sought to evaluate TLC as a continuous variable to determine a threshold below which the risk of PJI increases. The secondary aim was to quantify the predictive utility of TLC for the risk of PJI. Utilizing a national health care database that captures approximately 25% of inpatient procedures performed in the United States, we identified all adult patients undergoing total knee arthroplasty (TKA) and total hip arthroplasty (THA) between 2016 and 2023 who had a TLC value obtained one and 28 days, preoperatively. Restricted cubic splines were generated using logistic regression to assess the relationship between TLC and 90-day risk of PJI among the TJA, TKA, and THA cohorts. A receiver operating characteristic curve was created to further analyze TLC's predictive utility. A Youden index analysis was subsequently performed as a sensitivity analysis. In total, 54,019 patients (TKA: 64.1%; THA: 35.9%) were identified with preoperative TLC values, of whom 0.58% developed a PJI. The restricted cubic splines identified a threshold at 1,450 cells/μL, with confidence intervals spanning above and below an adjusted odds ratio of 1. The area under the curve of the receiver operating characteristic model was 0.495, indicating predictive power no better than chance. At a TLC of 1,450 cells/μL, sensitivity and specificity were 70.9 and 26.5%, respectively. Youden analysis for PJI yielded a threshold of 3,580 cells/μL, with an associated J statistic of 0.027. Procedure-specific subanalyses demonstrated a similar trend. Total lymphocyte count has no predictive utility for PJI following primary THA and TKA. We recommend against using TLC to risk-stratify patients prior to THA or TKA.