Diagnostic algorithm of the guidelines

NICE guidelines aim to standardise services implementing evidence-based recommendations. Following the diagnostic algorithm for chronic heart failure (HF) improves the patient’s chance to receive the correct diagnosis in a timely fashion.1 This is a pivotal step preceding the commencement of appropriate therapy. The diagnosis may lead to further investigations to subphenotype the HF. Besides, those with no HF will be reassured, and their further investigations into the causes of their symptoms may be instituted.

The guideline of 2010 introduced measurement of natriuretic peptide (NP) levels as the main gate into the HF diagnostic services and as a triage tool. The patients are thus divided into those who undergo echocardiography and receive specialist clinic assessment within 2 weeks (NTproBNP >2000 pg/mL) or within 6 weeks (NTproBNP 400–2000 pg/mL).1

Based on a health technology appraisal of the diagnosis of HF,2 the guideline introduced another port of entry into the diagnostic algorithm: history of myocardial infarction (MI). The guideline stipulated that in the presence of that history, there would not be a need to check NP. The aim was to reduce the financial burden of having to measure NP in all those with suspected HF. At that time, NP measurement was available to less than a third of the health communities in the UK.

Lessons learned from Zheng et al in this issue of the Journal

Zheng et al provided their real-world experience of the 2010 NICE guideline’s HF diagnostic algorithm.1 In their observational study, they reported the characteristics of the patients referred to the diagnostic HF services in two cities in the South West of England (Portsmouth and Southampton).3

Their patients reflected the community, being older (mean (SD) age 79 (9) years) than we saw in most of the HF trials, with more women (53%) than men.3

Compared with those with no HF, the group with HF had significantly higher incidence of diabetes mellitus, atrial fibrillation (AF) and history of prior MI.3 Unsurprisingly, those with HF had significantly higher NTproBNP than those with no HF.3

The patients entering the service through the 2-week pathway had a significantly higher incidence of AF and history of prior MI than those referred via the 6-week pathway.3 In contrast, significantly more patients using the 6-week pathway were hypertensive (72% vs 61%).3 There was no statistically significant difference in the incidence of diabetes mellitus between the patients using the two pathways.3

The authors made an interesting observation: contrary to the recommendation by the guideline, the general practitioners (GPs) referring to both centres had checked the NTproBNP in many of the patients who had a prior MI.3 There may be little practical relevance to investigating this tendency by the GPs further, as the 2018 NICE guideline made raised NTproBNP the single port of entry into the HF diagnostic service.4

The HF diagnoses made by the authors differed according to the entry pathway into the service: HF with reduced ejection fraction (HFrEF) was diagnosed in 43% of the group using the 2-week pathway and in 14% of those assigned to the 6-week pathway.3 HF with preserved ejection fraction (HFpEF) was identified in 30% and 22% of those accessing the 2-week and the 6-week pathways, respectively.3 Overall, HFrEF and HFpEF were found in 29% and 26% of the cohort, respectively.3 The latter point may reflect the rising incidence of HFpEF.5

Another achievement of Zheng and her colleagues is the provision of ‘real-world’ proof that the NTproBNP thresholds defining the two pathways are triaging patients into groups with varying incidence of HF. This lends practical support to these NICE recommendations.1 3

Are there questions raised by Zheng et al’s study?

Of the patients referred to their services, 53% had an NTproBNP >2000 pg/mL.3 However, as one expects the patients’ NTproBNP levels to follow normal distribution; the majority of these patients are expected to have had NTproBNP in the range of 400–2000 pg/mL.

The authors found HF in only 55% of the patients with NTproBNP >400 pg/mL.3 This is in contrast to the expected diagnostic yield of NP at that threshold, which is 76%.1 2

Another issue is the number of referrals received by the two centres. The two centres serve a combined population of 1 175 000 people. Portsmouth and Southampton contributed to the study for 35 months and 24 months, respectively. They reported receiving 1271 referrals. In contrast, in 30 months up to September 2014, we received in Sheffield 1785 referrals at a mean rate of 60 patients per month. Our centre serves a population of 551 800 people.6 Based on our experience, one would have expected Portsmouth and Southampton to have received 3705 referrals. Does this imply that the GPs had referred to the authors’ centres 34% of the expected cohort?

When comparing the 1-year all-cause mortality and the all-cause hospitalisation between those with HF and without HF, Zheng et al found no significant differences.3 The reduction of the risks of hospitalisation and mortality of HF can only be achieved by therapeutics of HFrEF. When the patients affected by HFrEF constitute only 29% of the total cohort, can we expect the treatment of less than a third of the cohort to have resulted in the reported equalisation of the risks of hospitalisation and mortality between those with and those without HF?3 Further work is needed in this field.

What could be done following the paper by Zheng et al?

The collaborators from Portsmouth and Southampton are to be congratulated on their achievements, which provided us with an opportunity to understand the implementation of the diagnostic algorithm of the NICE HF guideline in the real world. There are several lessons learnt from their work; however, it raises a few questions. The main question being is their experience representative of the whole country? Notably, the NICE guideline is applicable only to England and Wales.

Variations between centres are to be expected. While some may feel the aforementioned critique of the data presented by Zheng et al is provocative, it is important to recognise that each centre will be referred a cohort of patients that reflects the local population and is affected by local variables. These include the types of services provided in primary and secondary care and the different attitudes to referrals by GPs.

In order for one to have a truly representative picture of the country, two approaches could be followed. One is a national mandatory registry of every patient referred with suspected HF, implementing the NICE guideline. The second approach would be a funded multicentre study with centres representing all regions of the UK. The latter approach may be appealing for the rigorous nature of data acquisition, which will be centrally monitored and ratified. This approach could suffer from selection bias and sampling errors.

The former approach has its advantages and disadvantages. There is no doubt that fulfilling the demands of a national registry is tiresome and may not appeal to the busy clinician who is inundated with workload. There are measures that would enable the proper setting up of a registry. Entry of data into the registry should be an integral part of the clinician’s work. Thus, the data entry could replace the completion of the written medical notes and should obviate the need for dictation of the clinic letter. The database of the registry could be enabled to automatically import current medication lists as well as the results of electrocardiography, echocardiography and blood tests from existing electronic resources. The database could then automatically generate communication tools for the clinician with GPs, patients, HF nurses and rehabilitation teams. In addition, healthcare managers will be urged to consider the work on the registry an integral part of the consultation with the specialist in HF. All these measures may persuade the clinicians to adopt this approach. There are several local registries including the one we have in Sheffield.7

If the National Health Service was to adopt the proposed national HF clinics registry, support from the British Society for Heart Failure, the British Cardiovascular Society and the three Royal Colleges of Physicians would be vital for its success. The professional clout of these bodies could certainly be helpful if they were to support this proposed national HF clinic registry; this could be enforced if financial incentives could be added through linking part of the payment for the service to the degree of completion of the registry. Resources similar to the aforementioned proposal have been proven in other countries as a point of strength enabling epidemiological observational studies and also as a robust resource for renowned research studies.8