Therefore, this population was considered by the committee to be the most representative of current the population presenting to primary care in current UK practice. The committee raised concern about the low proportion of HF-REF patients identified in this study,. The committee considered that this may be due to study selection bias, as patients with severe symptoms, who are thought to be of high risk, are often not recruited into these types of clinical studies due to concern that there would be a delay in their treatment. 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. The committee acknowledged that the proportion of HF-REF patients in the heart failure population seems to be gradually declining, but still considered the proportion of HF-REF patients in the study to be low. The committee were concerned that this may bias the model results, as were there more clinical benefit to diagnosing heart failure the greater the benefit of earlier detection and therefore a lower NT-proBNP threshold. This effect was demonstrated in one of the sensitivity analyses (SA3): as the proportion of HF-REF in the model was increased, the cost effectiveness of 400pg/ml decreased although the ICER was still well below the 20,000 threshold. The committee also acknowledged that were there clinically effective treatment for HF-PEF patients, then a lower NT-proBNP threshold is likely to be most cost effective. Due to uncertainty around the diagnostic accuracy of the NT-proBNP test, two scenario analyses were undertaken to assess the diagnostic accuracy data and from two other study populations included in the clinical review. 