Diagnostic Value of Leukocyte Count, C-Reactive Protein, and Procalcitonin in Pediatric Liver Transplant Patients During the First Week Postoperative: A Longitudinal Study from a Tertiary Center and a New Diagnostic Method for Predicting Systemic Inf

<b>Background/Objectives:</b> Infection is a major complication during the early postoperative period following pediatric liver transplantation (LT). Prompt diagnosis and treatment are essential to prevent death. We aimed to assess the diagnostic value of procalcitonin (PCT), white blood cell count (WBC), and C-reactive protein (CRP) levels for detecting bacterial infection and SIRS within the first week after LT. <b>Methods:</b> Demographic data, vital signs, laboratory results (PCT, CRP, WBC), and culture findings on the 1st, 4th, and 7th days between January 2010 and 2024 were collected retrospectively. <b>Results:</b> The study included 88 patients. Seventy-two percent had cirrhotic liver disease. SIRS was present in 17% (n = 15), and bacterial growth was detected in 20% (n = 18). Bacterial growth was found in 80% of patients with SIRS (n = 12/15) and in 8% of SIRS-negative patients (n = 6/73). PCT levels were significantly elevated on days 1, 4, and 7, and CRP levels on days 4 and 7 in patients with SIRS. PCT elevation was significant on days 1, 4, and 7, while WBC increase was noted on day 7 in patients with bacterial growth. Body temperature ≥ 37.1 °C and PCT ≥ 5.1 ng/dL on the first day together showed a sensitivity of 72.2% and specificity of 84.3% for bacterial growth. Similarly, body temperature ≥ 37.1 °C and PCT ≥ 9.2 ng/dL on the first day yielded 73% sensitivity and 95% specificity for diagnosing SIRS. Cirrhotic patients exhibited limited or no WBC response to bacterial growth. <b>Conclusions:</b> PCT, CRP, and WBC alone are insufficient for diagnosing infection. Combined assessment of body temperature changes and PCT elevation may serve as more accurate indicators. Nonetheless, close monitoring of culture results and clinical signs, with serial physical exams, can aid timely infection management or prevent unnecessary antibiotic adjustments.