Introduction Circulating levels of beta-type natriuretic peptide (BNP) are increased in conditions characterized by volume overload and are an established tool for the diagnosis of acute congestive heart failure (CHF). However, there are clinical circumstances associated with moderately elevated BNP in the absence of acute CHF. There are a limited number of studies identifying different independent predictors of nonspecific elevation of BNP. The characterization of clinical conditions leading to moderately elevated BNP results would allow better interpretation and application of the BNP assay and perhaps influence clinical decision making in ER.
Aim To characterize the patients with elevated BNP and to determine physician behavior patterns pertaining to evaluation of patients presenting with shortness of breath in the emergent setting.
Material and Methods This is a retrospective observational study of patients presenting to the ER for various reasons who had BNP assays with intermediate elevation (100-500 pg/mL). Laboratory database from UMC, Fresno, was tapped to obtain list of BNP assay done between March 2003 and 2004. Records of patients with BNP values in the intermediate range were analyzed, including demographic characteristics, medical history, baseline lab work, EKG, ECHO, and discharge diagnosis.
Results A total of 399 records with BNP values of interest were identified and 258 were available for the review process. Out of 258 records, echocardiography data were available on 159 of which 62 had left ventricular dysfunction (LVD). 75 records carried a discharge diagnosis of CHF. The ECHO diagnosis of LVD and discharge diagnosis of CHF did not show 100% correlation. Of the 258 records that did not carry a discharge diagnosis of CHF, the following discharge diagnoses were noted: anemia (5.81%), atrial fibrillation (7.36%), renal failure (7.75%), pneumonia (8.52%), and COPD exacerbation (4.65%). There was no significant difference between the mean BNP levels amongst all these diagnoses including LVD by ECHO. Notably, 46.5% of 258 records had the chief complaint of shortness of breath.
Conclusion Moderate elevation of BNP can be found in the following clinical circumstances independent of LVD-anemia, atrial fibrillation, renal failure, pneumonia, COPD exacerbation, and hypertension. Nearly half the patients presenting to the emergency department who had a BNP level drawn did not have shortness of breath as their chief complaint. Since the BNP as a marker for CHF was established only in the setting of patients presenting with acute dyspnea, one should use caution in interpreting BNP levels when they are drawn in other settings that alter the pre- and post-test probabilities of a positive test.
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