The predictive prognostic values of serum interleukin-2, interleukin-6, interleukin-8, tumor necrosis factor-α, and procalcitonin in surgical intensive care unit patients

BACKGROUND: The pathophysiological roles of serum cytokine levels in critically ill surgical patients has yet to be determined. This study aimed to determine the predictive prognostic values of serum interleukin IL-2, IL-6, IL-8, tumor necrosis factor-α (TNF-α), and procalcitonin (PCT) in surgical intensive care unit (ICU) patients. METHODS: Cytokine concentrations were measured with an IMMULITE 1000 Immunoassay System (Siemens Healthcare Diagnostics GmbH, Berlin, Germany). The study population was divided into quartiles according to the patients’ cytokine levels: Q1, Q2, Q3, and Q4. The optimal cutoff values of IL-2, IL-6, IL-8, TNF-α, and PCT level for predicting mortality were established by drawing receiver operating characteristic curves. RESULTS: The levels of IL-2 in Q3 [odds ratio (OR) =4.434, 95% confidence intervals (95% CI): 1.527–12.874] and Q4 (OR =7.715, 95% CI: 2.744–21.693) were significantly higher than those in the Q1. The same results were noted in IL-6 and IL-8, and only Q4 (OR =2.383, 95% CI: 1.419–4.001) showed significance in the level of TNF-α. For IL-2, a cutoff value of 930.5 U/mL yielded a sensitivity of 69.39% and a specificity of 80.16% for the prediction of clinical outcome [area under the curve (AUC): 0.822; 95% CI: 0.789–0.855]. For IL-6, a cutoff value of 50.95 pg/mL showed discrimination ability, yielding a sensitivity of 71.43% and a specificity of 61.75% for (AUC: 0.704; 95% CI: 0.660–0.748). For IL-8, a cutoff value of 44.1 pg/mL yielded a sensitivity of 57.82% and a specificity of 79.58% for predicting clinical outcome (AUC: 0.753; 95% CI: 0.713–0.793). For TNF-α, a cutoff value of 11.95 pg/mL yielded a sensitivity and specificity of 68.66% and 72.90%, respectively, in predicting clinical outcome (AUC: 0.758; 95% CI: 0.717–0.800). The positive likelihood ratios for IL-2, IL-6, IL-8, and TNF-α were 3.50, 1.87, 2.83 and 2.53, and the negative likelihood ratios were 0.38, 0.46, 0.53, and 0.43, respectively. CONCLUSIONS: In critically ill patients, high levels of IL-2, IL-6, IL-8, and TNF-α in the first 24 h postoperatively were associated with clinical outcome. However, the effect of PCT level on prognosis still requires further study.