Sensitivity analyses were also undertaken in areas of uncertainty to see how robust the model results are. The base-case results are presented below. For a full write up of the model results and sensitivity analyses see Appendix O. In the base-case analysis 400pg/ml was found to be the most cost effective NT-proBNP threshold. Results are summarised below in Table 15 with regards to costs, QALYs and cost-effectiveness (net monetary benefit, and probability of cost effective at 20,000 per QALY threshold), and Table 16 with regards to ranking of the strategies. 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 probability of 400pg/ml being the most cost effective option at 20,000 per QALY is 77%. Table 15: Base case analysis results (probabilistic analysis) Diagnostic strategy Mean per patient NMB at threshold Probability most CE option at 20,000 per QALY Costs QALYs Chronic Heart Failure Diagnosing heart failure Diagnostic strategy Mean per patient NMB at threshold Probability most CE option at 20,000 per QALY Costs QALYs Abbreviations: CE = cost effective; QALYS: quality adjusted life years;.NMB: net monetary benefit. Table 16: Base case analysis ranking results Diagnostic strategy Probability Probability Probability Probability The mean costs and QALYs from the probabilistic analysis have also been presented graphically on the cost-effectiveness plane in Figure 5. The cost-effectiveness ratio of 400pg/ml versus echo all is 5,496. Figure 5: Base-case cost-effectiveness plane showing incremental costs and QALYs of each diagnostic strategy Chronic Heart Failure Diagnosing heart failure The disaggregated costs and QALYs from the probabilistic base case analysis are summarised inTable 17, Table 18 and Table 19 below. 