Background: Left ventricular dysfunction (LVd) is the main predictor of mortality in Chagas disease (ChD).
Aims: To compare the diagnostic performance of the conventional approach (ECG and chest X-ray) in the recognition of LVd in ChD, with a new strategy, in which BNP is measured in patients with an abnormal ECG.
Methods: Consecutive ChD patients recruited at an Outpatient Reference Center in Belo Horizonte, Brazil, without other systemic diseases, in 1998-99 (sample 1, n = 165) and in 2001-02 (sample 2, n = 62) underwent ECG, chest X-ray, BNP measurement and echocardiography.
Results: The prevalence of LVd (ejection fraction <or=0.40) was 9.1% in the sample 1. The conventional strategy recognized all patients with LVd (sensitivity: 100%, 95% CI: 79.6-100% and negative predictive value -PV 100%, 92.1-100%), but with low specificity (30%, 95% CI: 23.2-37.8) and +PV (12.5%, 95% IC: I7.7-19.6). The BNP/ECG strategy showed significantly better specificity (96.0%, 95% CI: 91.5-98.2, p < 0.001) and +PV (66.7%, 95% CI: 43.7-83.7, p < 0.001), and non-significantly lower sensitivity (80.0%, 95% CI: 54.8-93.0, p = 0.25) and -PV (98.0%,95% CI: 94.2-99.3, p = 0.08). Overall accuracy was improved with the new strategy. (94.5%,95% CI: 90.0-97.1 x 36.4%, 95% CI: 29.4-43.9, p < 0.001). Similar results were obtained for the sample 2.
Conclusions: The BNP-based strategy was more accurate than the conventional approach in the detection of LVd in ChD patients and should be considered as a valid option.