Uncertain benefits of BNP blood tests to monitor heart failure treatment
In specialist clinics, using B-type natriuretic peptide (BNP) blood levels to guide treatment in people with chronic heart failure shows promise but did not improve survival for all groups. In this review, the benefit was only seen in patients aged less than 75, who survived an extra 1.5 years on average, and possibly those with poor heart function (reduced ejection fraction). However, there was a reduction in hospital admissions for heart failure for everyone.
BNP is a hormone released from the heart muscle, and higher levels may indicate more severe disease. It is currently used for diagnosis, but its use in monitoring treatment has become the subject of recent research interest.
This research pooled data for 3,074 patients in 13 trials who were randomised to the blood test-guided or symptom-guided therapy and separately studied general practice data for a further 17,095.
The research was limited by the quality of the previous trials, the availability of data and the scarcity of monitored patients in general practice. Furthermore, there was no apparent mechanism found that could explain the small benefit. So, these findings should be regarded as tentative and are not conclusive enough to support a change in practice. Other research is underway that may better define the place for this test.
Heart failure is a condition where the heart cannot pump blood efficiently enough to meet the needs of the body. It has many causes, commonly, previous heart attack or high blood pressure. The 2010 National Heart Failure Audit estimated that one in 100 people in the UK has heart failure. It has a poor prognosis; around a third of people admitted to hospital with heart failure die within one year. Management currently costs the NHS around £625 million a year. The number of cases is expected to rise with the ageing population.
BNP is released from the heart muscle when it is stretched and under tension. Titrating medication to a pre-defined BNP target is a potential way to optimise treatment. However, it is unclear whether this is better than relying on symptoms alone, particularly in older adults and those with other illnesses.
This programme of work set out to assess the clinical and cost-effectiveness of BNP-guided therapy for people with a new diagnosis of heart failure between January 2007 and March 2013.
What did this study do?
The first part was a systematic review including 13 (non-UK) randomised controlled trials comparing BNP-guided therapy with symptom-based therapy in 3,074 people with heart failure. Five trials had individual patient data available, and most treated to a BNP target. Lack of blinding and variable study methods were common limitations. Younger patients also tended to have poorer heart function, and have fewer other conditions than older patients so may not be representative.
Secondly, a cohort study assessed data for 17,095 patients collected by the general practice Datalink registry and National Heart Failure Audit. Researchers compared people receiving BNP monitoring (regular BNP tests over six month’s observation period or longer), BNP testing (one test or more but not meeting the criteria of regular monitoring) or no testing.
What did it find?
The systematic review found:
- BNP-guided therapy had no overall effect on risk of death from any cause (hazard ratio [HR] 0.87, 95% confidence interval [CI] 0.73 to 1.04). Sub-group analysis found it reduced mortality for participants aged less than 75 years (HR 0.70, 95% CI 0.53 to 0.92) but not for older patients.
- BNP-guided therapy reduced the risk of hospital admission for heart failure (HR 0.78, 95% CI 0.65 to 0.95) but did not affect overall hospital admission (HR 0.97, 95% CI 0.85 to 1.10).
- In the cohort study, the overall death rate was 142 patients per 1,000 per year. Death rates were higher in the BNP-monitoring group (187 per 1,000 per year) than in the BNP-testing (131 per 1000) and never-tested groups (144 per 1,000). This probably reflects that this small group were sicker than other patients.
What does current guidance say on this issue?
The 2010 NICE guideline on the management of chronic heart failure recommends that BNP (or its derivative N-terminal pro-Btype natriuretic peptide, NTproBNP) is measured in people with suspected heart failure who have no history of heart attack. Urgent referral and echocardiogram assessment are recommended for those with a BNP level above 400pg/ml. Levels below 100pg/ml are said to make the diagnosis of heart failure unlikely.
Monitoring recommendations include a requirement for regular clinical assessment of functional capacity, fluid status, heart rhythm, cognitive and nutritional status for all patients with chronic heart failure (but not BNP).
What are the implications?
The study does not appear to support a change to clinical practice.
BNP monitoring could be effective for younger patients with reduced ventricular ejection fraction. However, the population with heart failure that is difficult to manage is frequently older and often have other illness besides heart failure.
Trials were conducted in specialist clinics, used a variety of BNP monitoring methods, and did not identify a BNP target to treat. This research is promising, but further evaluation of which people with heart failure might benefit is probably required before this becomes standard practice.
For more details click on the link : doi: 10.3310/hta21400.
This article first appeared in NIHR Signals.