At a threshold of 400pg/mL, the committee also noted that specificity was likely to be much higher (82% (52%-95%)) compared with specificity at the which would reduce any clinical harms of over-referral. The committee discussed possible reasons for the inconsistency between the study results at length, and considered that the differences in sensitivity and specificity were likely to be due to heterogeneity in the study populations. Chronic Heart Failure Diagnosing heart failure NICE 2018. All rights reserved. Subject to Notice of rights. ISBN: 978-1-4731-3093-7 The committee discussed the differences in setting between the studies as there was one Spanish study, one UK study that recruited patients between 2001 and 2003, and one recent UK study. The committee considered that across these settings the population presenting to primary care with signs and symptoms of heart failure could be different. The committee also noted that the proportions of HF-REF and HF-PEF across these studies were very different, supporting the hypothesis that the study populations were not similar. The committee agreed that based on the clinical data alone, it was not possible to establish the threshold that provided the best overall trade-off between benefits and harms. The committee considered that an economic model was necessary to trade-off the benefits of a lower threshold against the potential increases in cost. For that reason, the most clinically and cost- effective threshold was identified as a priority for economic modelling. Suspected heart failure and CKD The committee discussed the evidence in a population of suspected heart failure and CKD. The committee noted that the only evidence available was for BNP at a threshold of 410 pg/mL. No evidence was available for NT- proBNP at any threshold. 