Stage 1: Identifying the research question

This scoping review aimed to determine the value of direct GP access to diagnostic imaging investigations. The following research question was formulated:

1. ‘What does existing literature say about the value of enhanced access to diagnostic imaging in General Practice?’

Stage 2: Identifying relevant studies

A preliminary search of key databases was performed on the 10/06/2022. Online databases searched included PubMed/MEDLINE, Cochrane Library, Embase and Google Scholar. Multiple search terms were used to generate a reading list. For this, key words were identified, and medical subject heading (MeSH) terms were generated. The search terms were grouped, with results requiring mention of one search term in each group to be included (see below).

((‘diagnostic imaging’ [Title/Abstract]) OR (‘x-ray’ [Title/Abstract]) OR (‘CT’ [Title/Abstract]) OR (‘CAT’ [Title/Abstract]) OR (‘MRI’ [Title/Abstract]) OR (‘DEXA’ [Title/Abstract]) OR (‘ultrasound’ [Title/Abstract]) OR (‘echocardiogram’ [Title/Abstract]) OR (‘radiology’ [Title/Abstract]) AND (‘general practice’ [Title/Abstract])

Several additional relevant articles were identified by hand-searching references.

Stage 3: Selecting studies

Titles and abstracts of identified studies were read by two reviewers (AP & JB) from the 13^th–15^th and 20^th–21st June 2022 respectively, and those deemed relevant to the study were selected for full-text review. Full text reviewing was conducted by one reviewer (AP) from the 22^nd–27^th June 2022. The PRISMA Extension for Scoping Reviews (PRISMA ScR) flow diagram outlines the study selection process (Fig 1). Consistent with the scoping review methodology, inclusion criteria were broad to include a range of articles. Both peer-reviewed and grey literature were included. Literature was included irrespective of study design or methodology, resulting in various study types being included in the search. Once the initial search was performed, duplicates were removed, and studies were then included and excluded based on criteria described in Table 2.

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Fig 1. PRISMA ScR flowchart.

https://doi.org/10.1371/journal.pone.0281461.g001

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Table 2. Study inclusion and exclusion criteria.

https://doi.org/10.1371/journal.pone.0281461.t002

Stage 4: Charting the data

Once all relevant articles were identified, data were extrapolated and charted by one researcher to facilitate characterisation and thematic analysis of included studies. The following data was charted, as shown in Table 3:

• Author, year of publication
• Journal/ publication
• Study title
• Study population
• Imaging modality
• Study location
• Study design
• Intervention
• Outcomes Measured
• Major findings

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Table 3. Description of studies included.

https://doi.org/10.1371/journal.pone.0281461.t003

Stage 5: Collating, summarising, and reporting results

Data were collated, presented, and reported in the results section (see Table 3). Following this, major themes of the literature were identified using Braun and Clark’s ‘Thematic Analysis’ approach [19]. The Thematic Analysis method facilitates a systematic and thus replicable approach to the coding, synthesis, and interpretation of qualitative data. Whilst Thematic Analysis is mostly used to analyse interview data, the method also provides a useful framework for analysing non-interview qualitative data such as that reported in scholarly articles. The method entails completion of six stages, these being (1) familiarisation with data, (2) initial code generation, the (3) searching for, (4) reviewing of, and (5) defining of themes, and (6) report writing. No assessment of methodological quality was performed. Efforts to establish the value of enhanced access to diagnostic imaging were guided by the Donabedian model for establishing quality of care, with the structure, process and outcomes of such enhanced access initiatives being examined [20].

Stage 6: Consultation

In line with Levac et al.’s recommendations [18], experts in the field of General Practice were consulted to offer support with regards to the study’s aims and conduct. Consulted personnel assisted with decision making around choices whether certain studies were to be included and excluded for review and interpretation of study findings. For this review, select GPs from the Irish College of General Practitioners and the University College Dublin / Ireland East Hospital Group GP Research Network were consulted on an ongoing basis throughout June to September 2022.

Search results

Initial searches of the PubMed, Embase and Cochrane Library databases yielded 850 records published since 2012, with an additional 17 identified from hand searches. Following duplicate removal and reviewing of titles and abstracts, 113 were deemed relevant to the review and subject to full-text review. The search, identification and selection process are summarised in the PRISMA ScR diagram (Fig 1). Following this, 23 relevant papers were selected for final inclusion (Table 3).

Study design

The 23 studies included in this review used various study types. There were six cohort studies [21–26], four randomised controlled trials [27–30], four observational studies [13, 31–33], three cross-sectional studies [34–36], three questionnaire studies [6, 37, 38], one retrospective analysis [39], one feasibility study [40], and one systematic review [3].

Seven studies were based in Denmark [21, 24–25, 28–30, 40], seven in the UK [3, 13, 23, 27, 36, 38, 39], six in the Netherlands [22, 26, 31–33, 35], two in Ireland [6, 37], and one in Italy [34].

The sample sizes of the studies ranged from 163 to 1,739,422 participants. Participants’ ages ranged across studies. All included studies examined populations over 16 years old.

Study population

Of the studies included, 17 examined populations with a specific diagnostic imaging modality. Five studies examined direct access to CT [25, 28–30, 36], four studies to MRI [22, 27, 31, 41], four studies to US [21, 24, 37, 40], three to echocardiogram (ECHO) [23, 26, 39], and one to X-ray [34]. The remaining six studies examined diagnostic imaging access in General Practice as a whole [3, 6, 32, 33, 35, 28]. Five studies focused on direct access to imaging in the context of managing non-specific and / or multiple different conditions [6, 32, 33, 35,37]. Four studies examined imaging for the management of lung cancer [28–30, 34], three focused on cancer in general terms [3, 25, 38], and two studied ovarian cancer [24–40]. Three studies concerned heart disease [23, 26, 39], and two focused on knee injury [27, 31]. Single studies examined direct access in relation to deep vein thrombosis [21], chronic headache [13], brain tumour [36], and spinal pathologies [22] respectively.

Interventions studied

A key element across all studies was the implementation of access to external diagnostic imaging services through direct GP referral. The structure of the referral process varied between studies depending on the healthcare system involved and the nature of established access pathways. Most studies involved direct referral to imaging within an external radiology department, independent of hospital-based specialist involvement or additional testing [13, 21–34, 36, 39, 40]. In conjunction with enhanced access for GPs, two studies involved educational seminars for GPs on disease diagnosis and management [27, 29].

Outcome measures

A range of outcomes were examined across included studies. One study assessed the feasibility of implementing a direct access pathway [40]. Another analysed utilisation of an established direct access pathway [29]. The cost effectiveness of direct access to diagnostic imaging was explored in four studies [13, 21, 23, 34]. Both GP and patient satisfaction with direct access referral pathways were examined in four studies [3, 13, 30, 32]. Time between GP referral to scan was assessed in three studies [21, 27, 32]. Of these, one study also examined time spent by patients at a scan through direct access referral [32]. Another study analysed times spent with hospital-based specialists due to a direct access CT pathway (30). Referral to EDs was examined in two studies [33, 37]. Four studies examined the appropriateness of such referrals [22, 25, 30, 37].

Key findings

This scoping review’s findings indicate that enhanced direct access to diagnostic imaging services within General Practice is a welcome, feasible, and with respect to health systems in their totality, a cost-effective measure that can often improve both system level and individual patient clinical outcomes (e.g., GP and patient satisfaction, scan waiting times, metrics illustrating referral processes). Both patients and clinicians have expressed satisfaction with direct access to imaging initiatives, particularly with regards to these interventions’ positive impacts on waiting times for scans and referrals, diagnostic capacity, and clinical resource management. The level of GP and patient engagement with direct access interventions in the studies examined was often high, indicating that diagnostic imaging interventions are well regarded by both patients and clinicians. The reviewed studies demonstrate that when supported with direct access, GP imaging referrals are generally appropriate, yielding high rates of positive diagnostic outcomes. Although, it should be acknowledged that appropriateness can be wide-ranging and multi-faceted in its meaning, and there is ongoing work to establish how best to appraise diagnostic imaging initiatives [42].

The findings also show that direct access to imaging can ensure more efficient use of technical and staff imaging resources, reduced hospital admissions, more timely diagnosis / earlier treatment for patients, and reduced overall costs within the health system. However, it is notable that much of the research examined focuses primarily on how direct access interventions impact on the health system at large and on hospital services. It is less clear how access to diagnostic imaging interventions impact on resources and costs specific to General Practice operations. It was also evident that most studies focused on the impacts of modality specific imaging with specific patient populations, that studies usually examined experimental direct access interventions rather than established frameworks, and that research comparing the accomplishments of direct access initiatives in public and private health systems, and across time, is lacking. Most studies included in this review documented direct access initiatives that were based in primarily state subsidised systems, and that were at a relatively early stage of implementation.

Comparisons with existing literature

The World Health Organisation’s overview of integrated care models describes community-based diagnostic imaging services as key to shifting the provision of care from acute to community settings [43]. Key Irish and international policy reports regarding direct imaging access initiatives for GPs share similar sentiments [7, 10, 12, 44]. This review’s findings suggest that implementation of such initiatives is likely to have positive effects due to speedier diagnosis in the community and a more balanced sharing of responsibilities within the health system. This may in turn ease pressure on secondary care resources, and with respect to the Irish context in particular, it may contribute to reducing public outpatient waiting times. Further, in a 2015 survey, Irish GPs held that diagnostic imaging would improve patient care across a range of clinical scenarios [6]. This review’s findings suggest that GPs accurately predicted the impact of such an initiative, especially with regards to the positive impacts on outpatient referrals and hospital admissions. Of course, not all researchers have communicated such positive views on enhanced GP access to imaging. For instance, Karel et al. (2015) contend that GP imaging referrals for knee and low back pain have “…little to no benefit” [15], while Sajid et al. (2020) claim that ‘unfettered” GP access to imaging is conducive to mass wastage of service resource and therefore potentially harmful to patient health [16].

Implications for future research and policy

This study’s findings indicate that direct GP access to imaging can yield many benefits, particularly with regards to increased satisfaction levels amongst patients and doctors, reduced waiting times and referrals, feasibility of implementation, and cost-effectiveness within health systems at large. However, as mentioned, there is comparatively little research focusing on the impact that direct access initiatives have on General Practice workload and resources specifically, and future research regarding this issue is needed. Other important avenues for future research include examining the effects of direct access to imaging in general rather than with regards to condition specific patient populations. Furthermore, valuable insights may be gained by evaluating existing diagnostic imaging pathways rather than shorter-term experimental pathways constructed solely for the purpose of research investigations. These findings indicate that health systems should continue to support diagnostic imaging pathways within Primary Care, for the benefit of patients, clinicians, and the overall health system. However, to make such initiatives sustainable, policymakers must also consider the opportunity cost of increased imaging responsibilities within General Practice, namely increased burden on already strained GP resources. Ageing populations and GP recruitment challenges have led to a steadily increasing GP workload in recent years, and displacement of other work by such initiatives may occur. As to whether this leads to unintended consequences, separate to effects of the imaging initiatives themselves, must be carefully assessed.

Methodological considerations and limitations

The adoption of a scoping review methodology benefitted this study as the method permitted mapping of the literature concerning direct access to diagnostic imaging within Primary Care and General Practice settings, thus allowing us to provide a clear overview of a research topic that has not been widely investigated. Arksey and O’Malley’s scoping review framework ensured that our research development, study selection, and data interpretation processes were conducted using an accepted and rigorous approach. There were some limitations to our review which should be considered. For instance, unlike a systematic review, a scoping review does not include an assessment of study quality as the focus is on covering the range of work that informs the topic rather than limiting the work to studies that meet pre-specified standards of scientific rigour. Further, only articles written in English and published in the last ten years on four electronic databases were considered for this review which may have resulted in the exclusion of relevant studies. For instance, all included studies were based in European countries and so understanding of direct GP access initiatives in non-European contexts remains a significant knowledge gap worth investigating in future research. Notwithstanding these limitations, the 23 studies included allowed us to gain a comprehensive overview of the current literature, identify research gaps, and inform future research on this topic.