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BNP B-Type Natriuretic Peptide Testing for Diagnosing Congestive Heart Failure (CHF)
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Louise Diehl-Oplinger, RN,MSN,CCRN,APRN,BC
B-type natriuretic peptide (BNP) is a normally occurring hormone that is secreted by the cardiac atria and ventricles. It rises significantly in pathologic conditions of increased cardiac wall stress (volume expansion and pressure overload) such as congestive heart failure (CHF). Measuring BNP has become valuable in diagnostic screening to aid in the identification of patients whose dyspnea is a result of CHF. Therefore, the BNP should be ordered when it is unclear as to the cause of the dyspnea. It can also be used to help differentiate between CHF and chronic fibrotic lung changes, or an exacerbation of COPD, which can present very similar clinically. The negative value of BNP are values under 100 picagrams/mL. The finding of a low level of BNP less than 50 pg/mL is good evidence of the absence of heart failure as the cause for dyspnea. Heart failure and left ventricular dysfunction is becoming a major epidemic in the U.S. and the trend is increasing as we live longer. 5 million have been currently diagnosed and there will be approximately 500,000 new cases diagnosed each year! This diagnosis is the most common reason for hospital admission in the elderly. At present the death rate for CHF is 10% after one year and one half having this diagnosis will be dead in 5 years. Along with the persons’ quality of life are the high medical costs associated with treating this disease. The use of BNP testing is now used to not only diagnose and help health care providers treat this disease, but also to predict the long term mortality of it. The use of BNP testing is now being incorporated into treatment guidelines and correlates with the NYHA (New York Heart Association) classification and prognosis of heart disease. Multiple studies have shown that BNP testing has a 94% sensitivity, a 94% specificity and a 96% negative predictive value. It has also been found to be more accurate than history taking, physical examination findings, symptoms, Chest X-ray and EKG. In some research studies it was shown that CHF was misdiagnosed with the typical Chest X-ray and EKG a great deal of the time but a BNP level ruled in CHF. These findings have shown how invaluable BNP is and that the earlier it is performed and used, the earlier CHF can be diagnosed and managed for more favorable outcomes. A level of < 100 rules out CHF. The assay is easy to perform, takes only 15 minutes ( turn around goal is < 60 minutes) and costs only around $26.00. Current recommendations are to combine this testing with the physical examination findings, and other diagnostic studies for optimal diagnostic results. The test was designed to be run at the bedside as a rapid assay, however many facilities do not even have the capability of performing a laboratory BNP. Check with your facility whether they have the capability of performing a BNP prior to ordering it. Many facilities have to send the specimen out to an outside lab for analysis, requiring several days for turnover. This defeats the purpose for rapid diagnosis of a CHF patient. Remember ! - The BNP is to aid the health care provider in diagnosing the patient and is to be correlated with clinical observations.
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