Longitudinal Changes in Serum Procalcitonin After Bariatric Surgery and Their Associations with Anthropometric, Metabolic, and Inflammatory Parameters

Objective: Obesity is a systemic disease characterized by low-grade chronic inflammation and increased metabolic risk. Although bariatric surgery is known to improve metabolic and inflammatory status, the longitudinal behavior of emerging inflammatory biomarkers such as procalcitonin (PCT) remains insufficiently characterized. This study aimed to evaluate postoperative changes in serum procalcitonin (PCT) levels in patients undergoing bariatric surgery and to investigate their associations with anthropometric measurements, liver enzymes, and novel inflammatory indices. Methods: In this retrospective longitudinal cohort study, 38 patients who underwent sleeve gastrectomy and had complete preoperative and postoperative follow-up data at months 1, 3, and 6 were included. Anthropometric and biochemical parameters were analyzed, and systemic inflammation was assessed using PCT, Systemic Immune-Inflammation Index (SII) and the Systemic Inflammation Response Index (SIRI). Repeated-measures analyses were performed according to data distribution, and correlations were evaluated using Spearman analysis. Results: PCT levels showed a significant reduction at postoperative month 1 compared with the preoperative period. However, despite continued reductions in body weight, BMI, and fat mass at postoperative months 3 and 6, PCT levels plateaued without further significant change. In the preoperative period, PCT demonstrated strong positive correlations with liver enzymes (p < 0.01). At postoperative month 1, PCT was significantly associated with glucose and HbA1c levels. Although SII and SIRI decreased after surgery, no significant correlation with PCT was observed. Conclusions: PCT decreased in the early postoperative period after sleeve gastrectomy and may reflect early metabolic and inflammatory changes associated with rapid weight loss. However, its sensitivity for monitoring long-term inflammatory changes appears limited. The observed preoperative associations with liver enzymes may suggest a potential relationship between PCT levels, liver enzyme alterations, and metabolic alterations in obesity.