The committee considered that the patients considered to be of high risk are more likely to have HF-REF than HF-PEF. However, the extent of possible selection bias is unknown. Due to uncertainty around the diagnostic accuracy of the NT-proBNP test, two scenario analyses were undertaken to assess the diagnostic accuracy data from two other studies included in the clinical review (Verdu et al. 2012 and Zaphiriou et al. 2005). When applying the ordinal logistic regression model to the Verdu data to enable the results to be run probabilistically, the mean sensitivity values were not consistent with the reported study values. Therefore the Verdu study was run both probabilistically (using the ordinal logistic regression model data) and deterministically (using the reported study data). The inconsistency in the mean values from the regression model and those reported in the study was thought to be due to the fact that the sensitivity of 280pg/ml and 125pg/ml threshold were both 100%. Ordinal logisitic regression was thought to be the most suitable method to fit a distribution to the diagnostic accuracy data to ensure that the sensitivity and specificity values maintained their order according to the threshold level for each run. Using this method one assumes that the model is predicting values that the data would show if you had a greater sample size. The probabilistic analysis for Verdu supported the results of the base case analysis, showing that 400pg/ml was the most cost effective diagnostic Chronic Heart Failure Diagnosing heart failure NICE 2018. All rights reserved. Subject to Notice of rights. ISBN: 978-1-4731-3093-7 strategy (ICER: 9,842 per QALY gained). The probability of this being the most cost effective strategy at the 20,000 per QALY gained threshold is 62%. 