93 Utility of NT-BNP as a screening tool for cardiac dysfunction in patients with long-standing diabetes mellitus

Abstract

Background: Cardiac dysflmction (CD) is common in patients with long-standing diabetes mellitus and can lead to heart failure or sudden death. N-Terminal pro-Brain Natriuretic Peptide (NT-proBNP) may provide a screening method for the early detection and treatment of patients with CD but is confounded by renal dysfunction. Aim: To assess the utility of NT-proBNP for detecting CD in patients over 50 years of age with long-standing (> 10 years) diabetes. Method: A standard clinical history, current medications, height and weight were recorded for all patients. They underwent a blood test for NT-proBNP, routine haematology and biochemistry, lung function tests, 12-lead ECG and echocardiography. Results were compared with 100 normal subjects. Results: We invited 144 consecutive patients attending a long-term follow-up clinic for diabetes. 109 consented to participate. 37 patients had known IHD, 9 had LVEF 30, 46 had moderate or severe LVH, 5 had moderate or severe valve disease and 5 had a glomemlar filtration rate (GFR) of 330pg/ml, the 95th centile of the control group. An NT-proBNP cut-off value of 135 pg/ml provided a test specificity (SP) of 62% at a sensitivity (SN) of 100% (AUC 0.888) for the detection of LVEF<40%. Correction of NTproBNP for GFR and age improved test performance (SP = 68%, SN = 100%, AUC = 0.895) with a cut off value of 152 pg/ml. However, a better test performance was obtained using piecewise decision rules (see Table 1) for NT-proBNP and GFR (SP - 78%, SN = 100%). For a population of 1000, this would give a 42.7% reduction in false positive results from 349 (based on NT-proBNP only) to 149, with no increase in the number of false negatives. Table 1. Optimal Decision Rules for Detection of LVEF < 40% Decision rule Test result