Plasma calprotectin as infection biomarker in hip fracture patients: a prospective cohort study

Abstract

Background and purpose We aimed to compare the diagnostic performance of plasma calprotectin in detecting infections following hip fracture surgery with 3 other biomarkers: procalcitonin (PCT), C-reactive protein (CRP), and white blood cell (WBC) count. Methods This prospective cohort study included surgically treated hip fracture patients aged ≥ 65 years, admitted to our department from April 2023 to August 2024. Plasma calprotectin, PCT, CRP, and WBC count were measured on postoperative day 3. The outcome was any infection within 30 days (primary) and 7 days (secondary). Biomarker performance was evaluated using receiver operating characteristic analyses in a comparative framework. Results 166/550 individuals were analyzed (median age 85 years, 68% women). 19% (n = 31) and 12% (n = 20) had infection within 30 and respectively 7 days. For 30-day infections, calprotectin showed highest area under the curve (AUC) of 0.66 (95% confidence interval [CI] 0.54–0.77), followed by WBC count 0.60 (CCI 0.48–0.72), CRP 0.53 (CI 0.42–0.63), and PCT 0.51 (CI 0.40–0.63). Difference in AUC was largest between calprotectin and PCT (0.14, CI 0.00–0.29), followed by CRP (0.12, CI –0.01 to 0.26), while similar to WBC count (0.06, CI –0.05 to 0.16). For 7-day infections, AUCs were as following: calprotectin 0.70 (CI 0.58–0.82), WBC count 0.69 (CI 0.56–0.81), CRP 0.56 (CI 0.42–0.69), and PCT 0.48 (CI 0.33–0.63). Difference in AUC was largest between calprotectin and PCT (0.22, CI 0.05–0.39), followed by CRP (0.15, CI –0.02 to 0.31), while WBC count was similar (0.01, CI –0.09 to 0.12). Conclusion Calprotectin demonstrated a trend towards superior discriminatory ability for infections compared with PCT and CRP, particularly for infections within 7 days. Calprotectin provided moderate diagnostic accuracy, likewise WBC count.