In 2007, the American College of Cardiology Foundation (ACCF), in partnership with the American Society of Echocardiography, published appropriateness criteria for transthoracic echocardiography (TTE)1 and, a year later, appropriateness criteria for stress echocardiography.2 Both sets of criteria have been updated and combined into a single, recently published document.3 It remains a work in progress, but the areas of uncertainty become smaller with the acquisition of new evidence filling the gaps in knowledge. A wide array of cardiovascular conditions are covered by the document, which identifies five broad clinical scenarios for the possible use of clinical echocardiography:
- for initial diagnosis;
- to guide therapy or management, regardless of symptom status;
- to evaluate a change in clinical status or cardiac examination;
- for early follow-up, without change in clinical status; and
- for late follow-up, without change in clinical status.
The available evidence of the use of these appropriateness criteria in everyday clinical practice is reviewed in the present article. Moreover, it is relevant to understand the reasons why these criteria might be applied, or on the contrary disregarded or ignored.
The Appropriateness Criteria
The appropriateness criteria are scored as follows:
- appropriate imaging test for the specific indication (the test is generally acceptable and is a reasonable approach for the indication): median score 7–9;
- uncertain imaging test for the specific indication (the test may be generally acceptable and may be a reasonable approach for the indication; more research and/or patient information is needed to classify the test definitively): median score 4–6; and
- inappropriate imaging test for the indication (the test is not generally acceptable and is not a reasonable approach for the indication): median score 1–3.
It is quite clear that this division into three broad areas is somewhat arbitrary; however, this schematic approach is counterbalanced by the ease of use of the scoring system.
Appropriateness Criteria in Transthoracic Echocardiography
Only a few studies have applied the ACCF appropriateness use criteria (AUC) to everyday clinical practice.4 In a single-centre university hospital study, Ward et al. sought to prospectively evaluate the clinical application of the appropriateness criteria for TTE, and they concluded that the criteria encompass the majority of clinical indications for TTE and appear to reasonably stratify TTE ordering.4 In detail, among the 1,553 imaging tests for which a primary indication had been determined, 89 % were covered by the AUC. Of these, 89 % were appropriate and 11 % were inappropriate. The most common inappropriate indications are reported in Table 1. Imaging tests determined to be inappropriate according to the AUC were more commonly ordered in younger patients, outpatients and patients with a previous echo examination. When analysing the performance of the criteria, the authors showed that the frequency of new echo abnormalities was higher in the appropriate tests than in the inappropriate ones (52 % versus 29 %, p<0.001). Another important factor identified by the authors was the ordering physician’s profile. Inappropriate tests were less likely to be ordered by cardiac specialists compared with appropriate tests (42 % of inappropriate tests versus 51 % of appropriate tests, p=0.04). Overall, non-cardiac specialists ordered a higher frequency of inappropriate tests than cardiac specialists (13 % versus 9 %, p=0.04).
In the outpatient setting,5 Kirkpatrick et al. found the application of the appropriateness criteria quite disappointing for their clinical practice: they showed that, of 368 TTEs, 206 (56 %) were appropriate, 31 (8 %) were inappropriate and 131 (35 %) were unclassifiable. Moreover, appropriateness was not associated with new (odds ratio [OR] 1.23, 95 % confidence interval [CI] 0.48–3.18) or unexpected (OR 1.15, 95 % CI 0.38–3.52) findings. Provider type and level of training were not correlated with new or unexpected findings either. The authors question an extensive and uncritical use of the criteria, due to the high percentages of unclassifiable imaging tests and of relevant clinical information among the inappropriate tests. When the AUC were applied in totally different clinical settings – i.e., academic versus community practice – the frequency of appropriate and inappropriate outpatient TTEs was similar.6 Interestingly, Ward et al. also noted that the majority of inappropriate imaging tests in both practice settings were ordered to follow up a prior echo abnormality. For example, the most common inappropriate indication in both practice settings was routine yearly re-evaluation of patients with heart failure in whom no change in clinical status had occurred. It becomes relevant, however, to establish the clinical impact of the application of the criteria and the change of practice over time since their publication.
In a recent study, Rahimi et al.7 sought to identify the level of appropriateness, for outpatient TTE, of the 2007 AUC for TTE before and after their publication. Patients referred for outpatient TTE in the same period of the year (October) eight years apart were analysed. The authors demonstrated that there had been an 85 % increase in outpatient TTE volume and that the publication of the AUC had had no impact on inappropriate referrals, which were stable at between 13 and 15 % of the examined samples. These authors, again, stressed the fact that the areas of uncertainty were too numerous, making the AUC an unsuitable tool that needed refining.
The 2007 AUC were updated in 2011, and a few studies have been conducted since to ascertain the ability of these updated AUC to categorise indications not addressed by the older AUC. Parikh et al. found that, compared with the older AUC, applying the updated AUC demonstrated a lower rate of unclassified imaging tests (5.5 % versus 12.5 %, p<0.001), higher rates of appropriate (92.2 % versus 86.7 %, p<0.001) and inappropriate (1.8 % versus 0.8 %, p=0.046) imaging tests, and no significant change in the rate of uncertain imaging tests (0.5 % versus 0.0 %, p=0.157).8Figure 1 illustrates these results. According to this study, the number of unclassified imaging tests is reduced; still, a significant percentage remain unsettled due to the lack of evidence. Consistently with the results from Parikh et al., another study showed that the appropriateness classification of 148 (24 %) transthoracic echocardiograms was changed when using the updated AUC (p<0.001).9
Appropriateness Criteria in Transoesophageal Echocardiography
A few retrospective studies have addressed the feasibility of the 2007 AUC for TTE in transoesophageal echocardiography (TOE). Mansour et al.10 showed that 90.9 % of TOEs were ordered for indications outlined in the relevant section of the 2007 AUC for TTE. Of these, the vast majority were found to be appropriate (97.3 %), with only 0.8 % of inappropriate imaging tests and 1.9 % of uncertain tests. The most common indication for performing an adjunctive TOE (following an inconclusive TTE) was indication no. 31 (i.e., initial evaluation of suspected infective endocarditis [native and/or prosthetic] with positive blood cultures or a new murmur). Of all adjunctive TOEs, 71.3 % n=77 were performed following non-diagnostic TTEs, and 28.7 % (n=31) following TTEs with normal results because of a continued high clinical suspicion of a cardiovascular explanation for the stated indications. These results show that the 2007 AUC for TTE encompassed the majority of indications for TOE imaging ordered in routine clinical practice at a single-centre university hospital, and that the vast majority of the TOEs ordered for indications addressed in the AUC document were found to be appropriate (97 %). There remain a small number of TOEs (9 % of all TOE imaging tests) that are not addressed by the 2011 AUC for TTE, and have been covered in the 2011 updated document.
Other authors11,12 obtained results consistent with the study by Mansour et al.,10 showing a high level of appropriateness of the criteria in TOE. However, the available studies do not address how the application ofthe criteria modified the routine assessment of patients indicated for TOE. The high frequency of appropriate TOEs may be related to the limited number of indications for this technique and for the strict scrutiny to avoid totally inappropriate imaging tests (see Table 2).
Appropriateness Criteria in Stress Echocardiography
A few studies have addressed the feasibility of the AUC in stress echocardiography, showing a high frequency of inappropriate and uncertain imaging tests. Mansour et al.13 showed that, in a retrospective analysis of 289 imaging tests, 71 % were appropriate, 9 % uncertain and 20 % inappropriate (see Figure 2). The main inappropriate indications are reported in Table 3. Inappropriate tests were more likely to be ordered in younger patients and women. For stress echocardiography also, one of the main factors affecting appropriateness is the physician’s profile – cardiologists ordered inappropriate tests less frequently (see Figure 3). The frequency of abnormal test results was higher among the appropriate than among the inappropriate imaging tests (see Figure 4). In the study by McCully et al.,14 19 % (one out of five) imaging tests were unclassifiable, but the 2007 AUC had been used, and it seems likely that the percentage would be lower with the 2011 criteria. In the two studies (Mansour et al.13 and McCully et al.14), five clinical situations or indications accounted for nearly 70–80 % of all inappropriate tests, in most cases involving asymptomatic patients (see Table 3). Consistent results were obtained by other authors15,16 applying stress echo guidelines instead of AUC criteria, yet to be developed at time of studies. The frequency of inappropriate/uncertain imaging tests reached almost 40 %.
Appropriateness is the new imperative17 in contemporary medicine and is the fruit of a paradigm shift in healthcare, which links the boost in cardiac imaging to higher costs, increased risks and no real clinical impact. Appropriateness criteria have entered clinical practice and several retrospective analyses provide a static picture of how, in clinical practice, the level of inappropriateness remains high, influencing test results and increasing healthcare costs. These criteria still have areas of uncertainty that need to be filled with evidence obtained from clinical trials and meta-analyses. The conventional technology assessment should be applied to imaging techniques18 using the hierarchical model (first considering technical performance and safety, then diagnostic performance, diagnostic efficacy, treatment efficacy and patient outcomes, and finally societal effectiveness). However, the AUC have not been proved to significantly modify clinical practice, and prospective analyses should be conducted to demonstrate that the application of the criteria changes management and outcomes and significantly reduces healthcare costs. Unfortunately, no data are available on the prognostic impact of the application of AUC in coronary artery disease. A relevant and consistently demonstrated factor explaining the frequency of inappropriate imaging tests is the prescriber profile (non-cardiologists are more likely to order inappropriate tests). This may be due to a lack of familiarity with the cardiovascular guidelines available alongside the AUC documents. Interestingly, a few indications – including pre-operative evaluation (ordered mostly by anaesthesiologists) and stress testing in asymptomatic patients with a low pre-test probability – account for most of the inappropriate imaging tests. Again, this is one example of how a subspeciality bias may affect the appropriateness of stress testing, and specific training should be indicated to limit inappropriate imaging tests. Ad hoc training programmes may reduce the frequency of inappropriate tests ordered by non-cardiologists (see Figure 5).19
The implementation of appropriateness criteria should not be left in the hands of a few research laboratories, but strategies to reduce the increasing number of inappropriate imaging tests, with their downstream costs and risks, should become a major goal in clinical cardiology. Nowadays, the availability of high-tech imaging and its increasing and unrestricted use20 is shadowing simpler and less expensive technologies, such as ultrasound. In most cases, the new technologies are deployed in clinical practice before their incremental and additive value has been demonstrated through the conventional process of health technology assessment.21
The strategy for reducing inappropriate imaging tests could be implemented through the development of pre-testing decision-support tools to ensure that stress testing is appropriately ordered and the number of inappropriate tests is minimised, with a benefit for all the stakeholders involved. When referrals were filtered by cardiologists, the frequency of inappropriateness was significantly lower (see Figure 6).
A recent study at Harvard, conducted using a computerised radiology order entry system for outpatient computed tomography, magnetic resonance imaging and nuclear medicine examinations, resulted in a substantially decreased rate of low-yield imaging tests.22
In a new environment of healthcare cost containment and minimisation of risks related to imaging (such as ionising radiations),23 echocardiography with all its applications seems to be the appropriate tool to be implemented in everyday clinical practice due to its high diagnostic and prognostic yield, low cost, lack of ionising radiations and wide availability. The potential misuse and abuse of echocardiography, generating costs and risks, should be mitigated by the application of appropriateness criteria, still a perfectible tool for the lack of evidence in some clinical conditions.