PURPOSE: Serum brain natriuretic peptide (BNP) levels are currently in widespread use in emergency departments (ED) to aid in differentiating between dyspnea secondary to congestive heart failure (CHF) versus other causes. Measurements of the vascular pedicle width (VPW) >70 mm and cardio-thoracic ratio (CTR) >.55 on antero-posterior (AP) chest X-ray (CXR) also have been shown to correlate with patients volume status. The purpose of the study is not describe the correlation between objective findings on AP-CXR with BNP levels and to assess their accuracy in predicting BNP levels.
METHODS: Retrospective chart review of patients presented to the ED between August-September 2005 with dyspnea in whom a serum BNP and CXR was available. Of 112 patients, 65 patients were excluded (25 had postero-anterior CXR only, 3 had myocardial infarction, 23 had serum creatinine > 2 gm/dl and 14 patients had CXR and BNP on different dates).
RESULTS: 18/47 (38%) were 18 males. Mean age was 56.7 ± 12.6 years, mean ejection fraction (%) was 42.9 ± 24.6, mean BNP was 861 ± 1087 pg/mL, mean VPW was 67.4 ± 11.8 mm and mean CTR was 0.61 ± 0.007. Overall, there was a correlation between BNP and CTR (r2 = 0.6) but none between BNP and VPW (r2= 0.1). Using a cutoff point of CTR > 0.6 the sensitivity and specificity for predicting a BNP of > 230 was 82% and 95%, respectively. The positive likelihood ratio was 16 whereas the negative likelihood ratio was 0.19. The BNP levels for different categories of CTR (0.47-0.57, 0.58-0.68 and 0.69-80) were statistically different (Figure 1).
CONCLUSION: CTR > 0.6 strongly correlates with serum BNP levels and may therefore obviate the need for obtaining a separate BNP level.
CLINICAL IMPLICATIONS: Using CTR cutoff > 0.6 may help to minimize ordering unneccssory BNP levels in all patients who present to ED with dyspnea. This may help to decrease the cost of heart failure management.
DISCLOSURE: Ather Anis, None.