Optimal cut-off value of procalcitonin and procalcitonin/albumin ratio for predicting bacteremia among patients living with cancer: a test-negative case-control study.

Objective: The occurrence of bacteremia is critically important for the survival of cancer patients. Therefore, our study aims to evaluate the efficacy of procalcitonin (PCT) and the procalcitonin to albumin ratio (PAR) in predicting bacteremia among this population.

Methods: In this retrospective test-negative case-control study, we included 903 hospitalized cancer patients, divided into two groups: the bacteremia-positive group (BSI group,  = 384) and the bacteremia-negative group (non-BSI group,  = 519). We assessed the diagnostic significance of PCT and PAR through receiver operating characteristic (ROC) analysis and determined the optimal cut-off values using Youden's index.

Results: Both the duration of hospital stay and the 30-day mortality rate were significantly higher in the BSI group. The areas under the curve (AUC) for PAR and PCT were 0.749 (95% CI: 0.715-0.782) and 0.742 (95% CI: 0.708-0.776), respectively, indicating higher levels in the BSI group. The optimal cut-off values for predicting bacteremia were 0.72 for PAR and 1.32 for PCT. PAR showed the highest specificity (92.7%) and positive predictive value (PPV = 83.4%), while PCT demonstrated the highest sensitivity (51.3%) and negative predictive value (NPV = 71.6%).

Discussion: This study is the first in the literature to suggest that PAR and PCT are valuable biomarkers for diagnosing bacteremia in cancer patients. The identified cut-off values offer practical thresholds for bacteremia diagnosis.