Prospective validation of a predictive scoring system for deep sternal wound infection after routine bilateral internal thoracic artery grafting

Abstract

Objectives: The Gatti score is a weighted scoring system based on risk factors for deep sternal wound infection (DSWI) that has been specifically created to predict DSWI risk after routine bilateral internal thoracic artery (BITA) grafting. It has not undergone an external validation. The aim of the present study was to perform this validation.

Methods: BITA grafts were used as skeletonized conduits in 304 (90.7%) of 335 consecutive patients with multivessel coronary artery disease who underwent isolated coronary bypass surgery at the authors' institution between January 2014 and July 2015. Baseline characteristics, operative data and immediate outcomes of every patient were prospectively collected in a computerized data registry. A score was assigned to each patient preoperatively. The goodness-of-fit and the discrimination power of both models, preoperative and combined, of the Gatti score were assessed with the Hosmer-Lemeshow test and the calculation of the area under the receiver-operating characteristic curve, respectively.

Results: Eighteen (5.9%) patients suffered from DSWI. Major differences were found between the original series whence the Gatti score has been derived and the present prospective series. The Gatti score goodness-of-fit was satisfactory for both the preoperative (P = 0.61) and the combined model (P = 0.81). The area under the receiver-operating characteristic curve was 0.82 (95% confidence interval: 0.72-0.91) for the preoperative model and 0.8 (95% confidence interval: 0.71-0.9) for the combined model.

Conclusions: On the basis of the results of the present prospective study, the Gatti score has proved to be effective in predicting DSWI following BITA grafting despite some differences between the original and the present series of patients. More studies have to be performed in order to strengthen the evidence of this first external validation.

Keywords: Arterial grafts; Coronary artery bypass grafts; Quality improvement; Sternal wound infection.

Figure 1:

The Gatti score. The preoperative and the combined model in the prospective series (301 patients; AUC = 0.82, 95% CI: 0.72–0.91 vs AUC = 0.8, 95% CI: 0.71–0.9; P = 0.62). AUC: area under the receiver-operating characteristic curve; CI: confidence interval.

Figure 2:

The Gatti score. The preoperative and the combined model in the original series (2872 patients; AUC = 0.72, 95% CI: 0.7–0.73 vs AUC = 0.73, 95% CI: 0.72–0.75; P = 0.25). AUC: area under the receiver-operating characteristic curve; CI: confidence interval.

Figure 3:

The actual rate of DSWI in the prospective series (301 patients) and the expected DSWI risk according to the Gatti score (low, moderate and high risk). DSWI: deep sternal wound infection.