No evidence was available for NT- proBNP at any threshold. The committee considered advice from a renal physician co-opted to the committee and the very low quality evidence, and agreed that there was no convincing rationale to have a different test threshold for people with CKD and suspected heart failure. The committee noted that both advancing age and heart failure are associated with a gradual and progressive decline in renal function. In addition, the progression of heart failure and some treatments for heart failure lead to progressive deterioration of renal function. A decline in renal function is associated with increased fluid retention and a rise in the level of the serum natriuretic peptides, including NT-proBNP, even in the absence of heart failure. There is some evidence that the use of higher NT-proBNP thresholds would improve diagnostic accuracy for heart failure in people with significant deterioration of creatinine clearance. Suspected heart failure and AF No evidence was included in a population with suspected heart failure and AF. The committee agreed that in the absence of any evidence, there was no convincing rationale to have a different test threshold for people with AF and suspected heart failure. However the committee noted that atrial fibrillation can raise the level of serum natriuretic peptides, including NT-proBNP, even in the absence of heart failure. This is complicated further in heart failure with preserved ejection fraction, in which 2 echocardiographic diagnostic criteria become unreliable (the left atrial volume and the tissue Doppler imaging assessment of diastolic function). These factors contribute to the complexity of the diagnosis and have a potential impact on the usual thresholds for NT-proBNP in people who have atrial fibrillation. This has been recognised in several ongoing randomised controlled trials of heart failure, Chronic Heart Failure Diagnosing heart failure NICE 2018. 