Diagnostic and Potential in Assisting Therapeutic Decisions of N-Terminal Pro B-Type Natriuretic Peptide Levels in Patients with Suspected Congestive Heart Failure at Parirenyatwa Group of Hospitals in Harare, Zimbabwe

Background: Heart failure is a clinical syndrome caused by structural and functional defects in the myocardium resulting in impairment of ventricular filling and/ or the ejection of blood. Natriuretic peptides have emerged as important tools for diagnosis, risk stratification and therapeutic decision making for patients with heart failure. Relative changes in the amino-terminal pro B-type natriuretic peptide (NT-proBNP) levels may assist in the assessment of the risk of congestive heart failure (CHF). However, whether the levels can enable the prediction of outcomes with acute exacerbation at the time of admission remains unknown. This study seeks to determine the diagnostic and therapeutic potential of NT-proBNP in the diagnosis of CHF at Parirenyatwa Group of Hospitals. The study will also determine the correlation between NT-proBNP measurement and the gold standard method for the diagnosis of CHF. Methods: Patients suspected to have CHF who were admitted at Parirenyatwa Group of Hospitals’ medical wards and urgent care unit who had requests for echocardiogram were enrolled into the present cross-sectional study. All patients had dyspnoea of differing severity. The mean age of the participants was 71±7 years old. Demographic data was collected using a pretested interviewer-based questionnaire. Four millilitres of blood sample were collected from each participant into sodium citrate tubes and sent to GoPath Clinical Laboratories. Plasma levels of NT-proBNP were immediately measured, and other risk factors, symptoms and clinical data were also investigated. The sensitivity, specificity, diagnostic accuracy, positive predictive value and negative predictive value of the NT-proBNP assay amongst patients suspected to have CHF was determined. The performance of the assay was also evaluated against the gold standard method. Results: Of the 110 patients, 74 (67.3%) had CHF. The remaining 36 (32.7%) presented with dyspnoea of non-cardiac origin. Plasma NT-proBNP levels were higher in patients with CHF (492.5, IQR= 300.0 – 709.0 vs 49.5, IQR = 34.5 – 69.5; P<0.001), and increased as functional status deteriorated (P=0.0001). The area under the receiver operating characteristic curve was 0.9448 for the optimum cut-off value of 100 pg/ml. The sensitivity for this cut-off value for diagnosing CHF was 97.3%, the specificity was 91.7%, the positive predictive value (PPV) was 96.0%, and the negative predictive value (NPV) was 94.3%. Conclusion: Findings from the current study demonstrates the importance of plasma NT-proBNP in the diagnosis and exclusion of CHF in dyspnoeic patients. Plasma NT-proBNP has proved to be an important biomarker which can be used to assess diagnosis and severity of CHF as well as to potentially guide therapy in CHF patients. It is a simple, inexpensive, useful and highly effective diagnostic test for CHF. Although echocardiography remains the gold standard method regarding the provision of detailed information on cardiac performance and structure, imaging data alone is not sufficient enough to identify patients with adverse CHF outcomes. An integrated approach which can combine laboratory assays with imaging and clinical presentation will greatly improve the diagnosis of CHF.