Therefore the Verdu study was run both probabilistically (using the ordinal logistic regression model data) and deterministically (using the reported study data). The average estimates for the sensitivity and specificity values for Zaphiriou were consistent with the original data and were therefore only run probabilistically.The results of these analyses are presented in detail in Appendix O and summarised below. In the scenario analysis based on Verdu et al. 2012 deterministic analysis, 280pg/ml was found to be the most cost effective NT-proBNP threshold. 280pg/ml dominates 400pg/ml with higher mean QALYs and a lower mean cost, and extendedly dominates 125pg/ml. The incremental cost effectiveness ratio of 280pg/ml compared to echo all is 5,952 per QALY gained. In the scenario analysis based on Verdu et al. 2012 400pg/ml probabilistic anlaysis was found to be the most cost effective NT-proBNP threshold. A threshold of 400pg/ml produces both the highest incremental QALYs and the highest incremental cost versus echo all, and has the highest net monetary benefit at 20,000 per QALY and is therefore the most cost effective diagnostic threshold for referral to echocardiography. The cost-effectiveness ratio of 400pg/ml versus 280pg/ml is 9,842. The probability of 400pg/ml being the most cost effective option at 20,000 per QALY is 62%. In the scenario analysis based on Zaphiriou et al. 2005 280pg/ml was found to be the most cost effective. 280pg/ml dominates (more effective and less costly) 400pg/ml. The cost-effectiveness ratio of 280pg/ml versus 125pg/ml is 15,088. The probability of 280pg/ml being the most cost effective option at 20,000 per QALY is 19%. Chronic Heart Failure Diagnosing heart failure 5.1.5.3.3 Limitations and interpretation This analysis suggests that 400pg/ml is the most cost effective threshold for referring patients presenting to primary care with signs and symptoms of heart failure. 