Procalcitonin level for prediction of postoperative infection in cardiac surgery

Abstract

Background

Diagnosing infection after cardiac surgery remains difficult due to the systemic inflammatory response induced by cardiopulmonary bypass. We compared procalcitonin levels with white blood cell counts as predictors of infection after cardiac surgery.

Methods

We prospectively enrolled 100 consecutive adult cardiac patients. Postoperative white blood cell counts, serum procalcitonin levels, and blood cultures were examined.

Result

The sensitivity and specificity of white blood cell count and procalcitonin > 2 ng mL⁻¹ were 60% and 100%, 58.8% and 42.5%, respectively. Procalcitonin > 7 ng mL⁻¹ had 95% sensitivity and 80% specificity. Receiver-operating characteristic analysis showed a greater area under the curve for procalcitonin level (p < 0.0001) compared to white blood cell count (p = 0.31). Patients with positive blood cultures had significantly higher procalcitonin levels (51.97 ± 39.62 vs. 6.67 ± 10.73 ng mL⁻¹), Acute Physiology and Chronic Health Evaluation-II scores (16.95 ± 3.24 vs. 13.60 ± 2.98), and intensive care unit stay (6.35 ± 3.42 vs. 4.6 ± 2.2 days). Non-survivors had significantly higher Acute Physiology and Chronic Health Evaluation-II scores (19.09 ± 1.30 vs. 13.67 ± 2.97) and procalcitonin levels (43.83 ± 52.15 vs. 12.26 ± 19.89 ng mL⁻¹) but on logistic regression analysis, only Acute Physiology and Chronic Health Evaluation-II score was an independent risk factor for mortality.

Conclusion

The diagnostic accuracy of procalcitonin for bacterial infection is fairly high. Acute Physiology and Chronic Health Evaluation-II score is a better predictor of mortality and morbidity than absolute procalcitonin level. Procalcitonin > 7 ng mL⁻¹ can prognosticate and identify the high-risk group.