Diagnostic triage and the role of natriuretic peptide testing and echocardiography for suspected heart failure: an appropriateness ratings evaluation by UK GPs

INTRODUCTION

Diagnosing heart failure is difficult; it requires some objective evidence of cardiac dysfunction in the presence of symptoms and signs. Unfortunately, key indicators, such as dyspnoea, cough, or bilateral ankle swelling (BAS), are common and non-specific, with no single symptom or cluster of symptoms having sufficient predictive value for making a diagnosis.1–3 Moreover, interpreting such symptoms can be difficult in, for example, older patients or those who are obese.1,4

Reliance on symptoms and signs alone, which has been a standard way of labelling patients as having heart failure, can lead to both under- and over-diagnosis.5 As an example, many patients with peripheral oedema are, in the absence of testing, diagnosed as having heart failure when the oedema has another, unrelated aetiology.5 Another difficulty for GPs is distinguishing respiratory causes from cardiac causes of dyspnoea, in which symptoms of heart failure may be attributed to chronic obstructive pulmonary disease and, therefore, treated incorrectly.

In many parts of Europe, GPs are gaining enhanced direct access to investigations that improve the accuracy of diagnosing heart failure,6 namely natriuretic peptide (NP) testing and echocardiography; Box 1 outlines how these tests work. However, guidelines are not clear as to how these technologies should be applied in triaging patients with symptoms; as a result, their use is inconsistent across, and within, countries, including the UK. The ‘appropriateness’ of the use of NP testing and echocardiography is also largely opinion based, with hospital specialists being viewed as the ultimate arbiters of the appropriateness of testing decisions made by GPs.7

Some specialists have expressed concern about the overdiagnosis of heart failure by GPs who rely simply on routine clinical assessment8,9 when it might be more appropriate to arrange NP testing or echocardiography. However, others believe that such enhanced access might simply lead to more indiscriminate use of NP testing, with a consequent rise in false positives.11 As one of the symptoms of heart failure is fatigue, it is also quite possible to imagine that the current (and growing) battery of tests being ordered by many GPs for patients who are ‘tired all the time’ might be extended to include such items as C-reactive protein and NP.12

However, the precise definition and derivation of the term ‘appropriateness’ in studies examining GP testing is rather elusive.13 Appropriateness is not just about overuse or misuse, but should also consider underuse. For example, in a recent study of access to coronary angiography, it was demonstrated that many patients deemed appropriate for angiography failed to receive it and, as a result, experienced worse outcomes.14

In the absence of definitive guidance, the purpose of this study was, therefore, to derive appropriateness ratings for the use of heart-failure diagnostic triage in routine primary care. The aim was to identify the clusters of symptoms, patient characteristics, and electrocardiogram (ECG) results that GPs perceive as appropriate and inappropriate for referral for either NP testing or echocardiography as a diagnostic approach for heart failure. In addition, the study sought to identify those combinations of symptoms, patient characteristics, and ECG results for which uncertainty exists regarding the diagnostic pathway.

METHODS

The RAND Corporation has developed a definition of appropriateness in relation to GP-initiated testing:

‘For an average group of patients presenting to an average GP, clinically appropriate testing means that the expected health benefit(s) exceed the expected negative consequences by a sufficiently wide margin that the test is worth doing’.15

In conjunction with the University of California, RAND has developed a validated method to generate appropriateness ratings; this involves combining a summary of scientific evidence with the collective judgement of experts.16 For diagnostic testing, this presents an opportunity to produce a series of ratings of clinical scenarios regarding the appropriateness of performing a particular test in relation to patient-specific symptoms, patient characteristics, medical history, and previous investigations.17

This study adhered to the RAND Appropriateness Method17,18 by, initially, reviewing and collating the existing evidence base on heart-failure diagnosis, which included two recently published systematic reviews and their consultant papers.1,2 From this review, together with discussions with cardiologists and GPs, a list of clinical scenarios was generated that covered the major symptom-initiated presentations within general practice for patients with possible heart failure (but not already known to have heart failure), in whom NP testing or echocardiography might be considered (Table 1).

Four common presenting symptoms (cough, BAS, dyspnoea, and fatigue/tiredness), three levels of perceived risk of cardiovascular disease (CVD) (low, intermediate, or high), and dichotomous categorisations of CVD/chest examination and ECG result were identified. The symptom-initiated presentations were then used to develop a list of 540 clinical scenarios (Table 1).

Each scenario represented a separate testing indication consisting of variable combinations of the presenting symptoms, CVD risk, chest examination, and ECG result. Although sex was not explicitly included as a separate variable, it was incorporated in the assessment of CVD risk. The decision to use three levels of CVD risk was based on considerations about the nature of primary care diagnostics and study feasibility. More detail on the characteristics of these variables and the associated instructions given to panellists is provided in Table 1.

Each scenario was then independently linked to one of following three potential decisions that a GP might make:

• no further investigations (Nil) — to carry out neither echocardiography nor an NP test;

• echocardiography — to directly refer for echocardiography without carrying out an NP test; or

• B-type NP (BNP)/NT-proBNP triage (NP) — to first carry out an NP test in order to rule out those individuals at low likelihood of having heart failure. The remaining patients would subsequently go on to be referred for echocardiography.

A rating scale was used to rate these potential decisions in relation to the clinical presentation on a 9-point integer scale, as follows:

• scores 1–3: inappropriate next step (that is, no benefit, possible harms);

• scores 4–6: uncertainty about next step (that is, when harms and benefits are judged as approximately equal, or when the best available evidence does not support a judgement either way);

• scores 7–9: appropriate next step (that is, benefits were judged to outweigh harms).

As an example, a rating of 1 would mean that the decision would be an extremely inappropriate next step, whereas a rating of 9 would mean that it was extremely appropriate.

RESULTS

Results are presented for the ratings from the second round only and are summarised in Tables 2 and 3. The appropriate next steps are presented as matrices in Appendix 1.

Table 2 shows a summary of the panel ratings for the 540 separate scenarios and indicates a high level of agreement within the panel, with only 42 scenarios (7.7%) rated with disagreement. Of the 540 scenarios, 217 (40.2%) were rated as appropriate next steps without disagreement and 194 (35.9%) scenarios were rated as inappropriate next steps without disagreement. In all other scenarios (n = 129) the appropriate next step was considered equivocal.

Table 3 presents the ratings for all combinations of symptoms and tests, and shows, for each combination, which of the three next steps studied were rated as either appropriate or inappropriate; the overall panel median rating is given in parentheses. When the panel rated the cluster of symptoms and tests as an equivocal marker for referral for either NP testing or echocardiography, no next step is recorded.

Table 3 shows examples of scenarios in which the panel felt referral for either NP testing or echocardiography would be an inappropriate next step and that no investigation was an appropriate next step; for example, where there was a normal CVD examination, low CVD risk, and normal/no ECG status with either cough, fatigue, or BAS presenting as single symptoms. However, in this case where dyspnoea presented in combination with at least two other symptoms, NP testing was never rated as inappropriate.

There was only one example of NP testing being rated an appropriate next step and echocardiography as an inappropriate next step (normal CVD examination, low CVD risk, normal/no ECG status and presenting symptoms of cough, BAS, and dyspnoea). There were also examples of scenarios in which referral to NP testing was rated an appropriate next step but referral to echocardiography was considered equivocal (that is, normal CVD examination, low CVD risk, abnormal ECG status and presenting symptoms of dyspnoea and fatigue or cough or BAS [data not shown]). In general, the presence of dyspnoea was more likely to be associated with NP testing being an appropriate next step compared to no testing.

Table 3 also shows that there are no scenarios in which echocardiography was rated an appropriate next step but NP testing was not also considered appropriate. For many scenarios, echocardiography and NP testing were rated as equally appropriate next steps; however, in some scenarios, one test was considered more appropriate than the other (Table 3). In general, the presence of an abnormal CVD examination result, high CVD risk, and abnormal ECG status made referral to echocardiography a more appropriate next step than NP testing. In most scenarios representing normal or abnormal CVD examination results in combination with any risk of CVD and normal/no ECG status, NP testing was rated as more appropriate than echocardiography.

These ratings have been used to generate appropriateness matrices for single symptoms and combinations of symptoms (Appendix 1). Furthermore, in developing the appropriateness matrices, it also made clinical sense to combine the low and intermediate CVD risk categories. These matrices show where NP and echocardiography were rated the most appropriate next step, and where NP and echocardiography were rated as equally appropriate next steps.

DISCUSSION