This suggested that the study populations or other features of the study design or quality were contributing to differences between test accuracy at different thresholds, rather than these differences necessarily reflecting true threshold-related differences in test accuracy. Sensitivity analyses using just the data assessed as low risk of bias were conducted, to see if this resolved the inconsistency in the results, but the inconsistency between studies remained. Given the committee s ability to establish the most appropriate test thresholds was limited by the thresholds reported by the included studies, the committee decided to contact study authors seeking additional data at the particular thresholds. The committee decided to limit this request to data on NT-proBNP rather than BNP for the multiple reasons: 1. The clinical review demonstrates that NT-proBNP has a greater sensitivity over a range of thresholds compared to BNP. Chronic Heart Failure Diagnosing heart failure NICE 2018. All rights reserved. Subject to Notice of rights. ISBN: 978-1-4731-3093-7 The committee acknowledged the high sensitivity from one study conducted in 1997, but considered that the heart failure population has changed significantly since this study was conducted with a greater proportion of people with HF-PEF, which on a population level tend to have lower NT-proBNP levels than people with HF-REF . Therefore it is highly uncertain as to whether these results represent the diagnostic accuracy for BNP testing in current practice. Whereas, the majority of the high quality NT-proBNP studies are more recent studies and are more likely to be applicable to current practice. Comparing thresholds between BNP and NT-proBNP is inherently difficult as there is no conversion algorithm between them. However, the Zaphiriou study (high quality study assessing both BNP and NT-proBNP) assessed the recommended industry cut-offs for each test. 