• Vol. 52 No. 12, 651–659
  • 28 December 2023

Understanding the use of evidence-based medical therapy in patients with peripheral artery disease: A qualitative study using TCID Framework



Introduction: The global burden of peripheral artery disease (PAD) has been increasing. Guidelines for PAD recommend evidence-based medical therapy (EBMT) to reduce the risks of cardiovascular events and death but the implementation of this is highly variable. This study aimed to understand the current practices regarding EBMT prescription in PAD patients and the key barriers and facilitators for implementing PAD guidelines.

Method: A qualitative study was conducted in the largest tertiary hospital in Singapore from December 2021 to March 2023. The participants included healthcare professionals and in-patient pharmacists involved in the care of PAD patients, as well as patients with PAD who had undergone a lower limb angioplasty revascularisation procedure. Data were collected through in-depth, individual semi-structured interviews conducted face-to-face or remotely by a trained research assistant. Interviews were audio-recorded, transcribed and systematically coded using data management software NVivo 12.0. The Tailored Implementation for Chronic Diseases (TICD) framework was used to guide the interviews and analysis.

Results: Twelve healthcare professionals (4 junior consultants, 7 senior consultants, and 1 senior in-patient pharmacist) and 4 patients were recruited. Nine themes in 7 domains emerged. Only a small proportion of doctors were aware of the relevant guidelines, and the generalisability of guidelines to patients with complicated conditions was the doctors’ main concern. Other barriers included cost, frequent referrals, lack of interprofessional collaboration, not being the patients’ long-term care providers, short consultation time and patients’ limited medication knowledge.

Conclusion: Findings from this study may inform strategies for improving healthcare professionals’ adherence to guidelines and patients’ medication adherence.


What is New

  • Using the Tailored Implementation for Chronic Diseases (TICD) framework, this qualitative study examines healthcare workers’ and patients’ perceptions of the implementation of evidence-based medical therapy (EBMT) in the treatment of peripheral artery disease (PAD).

Clinical Implications

  • This qualitative study highlights existing barriers to the use of EBMT in PAD patients, including lack of guideline awareness, frequent referrals, the limited generalisability of the guidelines to all patients, and cost.
  • Future interventions, such as collaborative care and focused training, are needed to enhance EBMT utilisation in PAD management.

The global burden of peripheral artery disease (PAD) has been increasing, with 237 million adults living with PAD worldwide in 2015,1 rising from 202 million in 2010.2 A population-based study in Singapore found the overall prevalence in Chinese, Malays and Indians to be 3.5%, 5.2% and 5.6%, respectively.3 Given the increasing prevalence of diabetes in Singapore,4 it is unsurprising that there is an increasing number of PAD cases in the country. Apart from the risk of major amputation, PAD is strongly associated with increased cardiovascular morbidity and all-cause mortality.5 Despite its rising prevalence and adverse impact on quality of life, this condition remains underdiagnosed and undertreated.6,7 As part of the evidence-based PAD risk management, pharmacotherapy recommended by various internal guidelines includes antiplatelet therapy and statin agents in all PAD patients as well as antihypertensive and anti-diabetic medications as secondary preventative therapies.8-10

Despite clear guideline recommendations, EBMT implementation for PAD management is inadequate. A local drug utilisation study of EBMT in chronic limb-threatening ischaemia (CLTI) patients revealed that the use of statins and antiplatelets at admission for angioplasty was only 66% and 47%, respectively.11 Similarly, data from Danish nationwide administrative registries also showed that relative to coronary artery disease alone, patients with PAD and without history of coronary artery disease  were less likely to use any antiplatelet or statins at 18 months after diagnosis.12 However, EBMT use at discharge was strongly associated with 6-month post-procedural use for recommended medications.13 A retrospective analysis of EBMT use in patients undergoing lower limb angioplasty in our institution also found suboptimal EBMT use, especially statins, at discharge, indicating a potential opportunity for improvement.11

There have been studies examining the factors of non-adherence to cardiovascular disease guidelines,14,15 but there are few focusing on PAD guidelines. Moreover, most studies focused on patient factors alone,16,17 rather than taking a more systemic approach to investigate other factors that could potentially affect EBMT adherence. Using a comprehensive checklist, the Tailored Implementation for Chronic Diseases (TICD) checklist,18 allows us to study various determinants of the implementation of clinical practice guidelines systematically. The TICD checklist includes 57 potential determinants in 7 domains, namely, individual health professional factors, professional interactions, guideline factors, patient factors, incentives and resources, capacity for organisational change, and social, political and legal factors.

With the guidance of the TICD framework, we conducted a qualitative study in patients with PAD and healthcare workers (HCWs) interacting with PAD patients to understand the current practices regarding their EBMT prescription and investigate the key barriers and facilitators for implementing PAD guidelines.


Study design and setting

A qualitative study was conducted in Singapore General Hospital, the largest tertiary hospital in Singapore, from December 2021 to March 2023. In-depth, semi-structured interviews were conducted individually in person or remotely. This study was approved by the SingHealth Centralised Institutional Review Board (CIRB) [Ref No.: 2021/2746]. The Consolidated Criteria for Reporting Qualitative Studies guideline was used to guide the reporting of qualitative research.19


Study participants were recruited using purposive (i.e. non-random) sampling. We invited doctors from departments of endocrinology, vascular surgery, vascular intervention, internal medicine, renal medicine, vascular and interventional radiology, as well as inpatient pharmacists who interacted with PAD patients to participate in the study via email. PAD patients who had undergone a lower limb angioplasty and returned for their first follow-up appointment were also invited to participate. Eligible patients were identified by doctors and approached by research coordinators. Those who were not able to converse in either English or Mandarin were excluded.

Study procedures

We developed 2 structured interview guides based on the TICD framework, for healthcare professionals and patients, respectively. Before the interview commenced, written informed consent was taken by the research coordinators. Interviews were conducted face-to-face or via Zoom. All interviews were conducted by one of the authors, a trained research assistant who had no pre-existing relationships with the participants. All the face-to-face interviews were carried out in a private and conducive environment in the hospital using the interview guide. For interviews conducted remotely, written informed consent was taken prior to the day of the interview in person where possible. Each interview lasted 30–45 minutes and was audio recorded. Each participant was reimbursed for their time. Recruitment was continued until data saturation, which was determined by discussion among team members.

Data analysis

Data management was performed by NVivo 12 (QRS International, Burlington, Massachusetts). All English or Mandarin interviews were transcribed from audio file format to text using Otter.ai (Otter.ai, Inc, CA) or Sonix.ai (Sonix Inc, CA), respectively. The transcriptions were then manually checked and edited. Transcripts for interviews conducted in Mandarin were translated into English. Two investigators familiarised themselves with the transcripts to get a better understanding of the interviews and generate codes individually. The codes were then compared for their similarities and differences. Similar codes were clustered to create categories and themes. All disagreements were resolved through discussions among the authors. Data analysis was performed simultaneously with data collection, which continued until data saturation was reached, where no new codes were identified.


A total of 12 healthcare professionals (4 junior consultants, 7 senior consultants, and 1 senior in-patient pharmacist) and 4 patients completed the interviews. The majority of the HCWs interviewed were doctors (11/12), including nephrologists, vascular surgeons and consultants. Participants’ demographics are shown in Table 1. From the analysis, 9 themes in 7 TICD domains emerged (Table 2).

Table 1. Participant demographics.

Table 2. Tailored Implementation for Chronic Diseases (TICD) Framework analysis with inductively developed belief statements.

Domain 1: Individual health professional factors

Theme 1: Limited awareness of the relevant guidelines

The HCWs were familiar with the risks that PAD patients faced, in particular limb ischemia and limb amputation. They also cited that PAD patients had higher rates of cardiovascular outcomes and death and were more susceptible to infections. The participants were also familiar with PAD-related symptoms and the treatment. All the doctors interviewed reported that treatment consisted of statin and antiplatelets, as well as diabetic or blood pressure medications to treat the underlying cause.

Some participants, especially vascular surgeons, were aware of the relevant guidelines. One surgeon noted, “There is the European Society of vascular surgery, the Society for Vascular Surgery, there is the American Heart Association, and I’m sure there are more” (SGH-HCW-013, vascular surgeon). However, other participants acknowledged that they were not aware of any guidelines, nor had they kept themselves updated on the latest guidelines due to certain reasons. First, due to the frequent referrals they made, they did not find a need to read the guidelines. As a nephrologist said, “I do, however, know the basic principles of treating and when to refer the patients” (SGH-HCW-005, nephrologist). The second reason was that a major part of PAD management was to control cardiovascular risk factors. According to a nephrologist, “I didn’t really go to search the guidelines. But as long as I know [sic], we usually give to control [sic] the cardiovascular risk factors, such as giving the antiplatelets and statins to control cholesterol, optimise blood pressure and diabetes control”, according to a nephrologist (SGH-HCW-001).

Not being aware of the latest guideline was cited as one of the barriers to implementing EBMT.  A radiologist said, “[Consultants are] still only familiar with the evidence that when you were training [sic], and if your department isn’t doing regular updates or like continuing medical education events or people don’t share their knowledge, then that could be a potential challenge that I can see” (SGH-HCW-003, radiologist).

Domain 2: Professional interactions

Theme 2: Shared responsibilities in the PAD management across different departments

As patients with PAD generally have various comorbid conditions, disease management is often multidisciplinary, involving different specialists such as cardiologists, endocrinologists, obesity managers and allied health professionals (such as podiatrists).

On the departmental level, all participants denied the existence of a department protocol in the PAD department. Instead, doctors were allowed to make the judgment based on their own clinical acumen and online resources. Their practice patterns would also be influenced by their colleagues.

Theme 3: Doctors’ concerns about implementing EBMT due to polypharmacy and comorbidities

For safety reasons, inpatient doctors had concerns about starting patients on new chronic medication because they were not the patients’ long-term care providers. One participant, an internal medicine doctor, stated that “sometimes PAD is not the primary condition that the patient gets admitted. I do prefer not to rock the boat in other ways and just keep them in the care of their respective specialists” (SGH-HCW-006, internal medicine doctor). In addition, due to limited consultation time and a heavy workload, doctors were unable to educate the patients about the medication and ensure adherence. “[Specialists] will be able to explain to them why [they] need to continue it and make sure that they adhere to it. That’s the main reason why there’s poor compliance with the guidelines,” said a radiologist (SGH-HCW-008).

Domain 3: Guideline factors

Theme 4: Doctors’ mixed opinions on following the guidelines

The majority of the participants agreed on the recommended therapy and believed that the guidelines were, as a nephrologist noted, “useful in summarising the evidence and giving you a starting point” (SGH-HCW-007, nephrologist), and they would usually follow the guidelines “unless there’s some other reason for this patient not to be on them” (SGH-HCW-002, internal medicine doctor).

However, doctors also had concerns about following the guidelines. The major reason was that the guidelines may not apply to all their patients or the local context. According to a nephrologist, “Individuals themselves change over time. So, you have to adapt to their current status, which fluctuates hugely, especially [for] the elderly.” Another reason was that sometimes doctors had to weigh risks against benefits before making decisions. For example, for a patient with PAD who recently had a heart attack, while the doctor was clear that beta-blockers should be administered with extreme caution, he still had to initiate beta-blocker, because “you need it for its antianginal [properties], to reduce myocardial oxygen demand” (SGH-HCW-006, internal medicine doctor). The doctor explained that “Sometimes I might choose and decide that the heart is more important than the leg and start the beta blocker anyway” (SGH-HCW-006).

Domain 4: Patient factors

Theme 5: Lack of patients’ understanding of PAD and associated medications

Having had PAD for 2 to 10 years, all patients claimed that they were able to take their medications daily without any difficulties or reminders because it had become their routine. Said one patient (SGH-PT-002), “I consume them every day and I won’t forget to take them.” However, they denied that the purpose of taking medications was well explained as such knowledge was beyond their understanding. A patient noted, “The thing is very complicated. I will just take whatever medications that [doctors] prescribe to me” (SGH-PT-004).

Regarding patients’ adherence levels, HCWs’ estimations varied, ranging from ≤40% to >95%, which was judged based on each patient’s blood test results. Estimation of antiplatelet adherence was more difficult. On why patients had difficulty adhering to their medications, doctors listed multiple factors—including cost, polypharmacy, side effects, inconvenience of insulin injection, no effects, difficulties in behavior change, poor understanding and poor social support.

Domain 5: Incentives and resources

Theme 6: Cost and lack of time as main barriers to implementing EBMT

Cost was considered one of the barriers to adhering to the guidelines. Regardless of guidelines-recommended medications, doctors would prioritise the prescription of affordable medications, given the fact that “the most effective medicine is the one that the patient can actually afford, [that] he actually takes,” noted a nephrologist (SGH-HCW-007). Besides cost, a lack of time to check potential interactions was another barrier. “It takes ages to login into the Electronic Health Record system and we don’t have time for that. So, we just kind of prescribed [sic] whatever we think is the safest, most basic, and then we move on (SGH-HCW-007).”

Theme 7: Collaborative care to improve interprofessional communication and patient education

A group of facilitators frequently mentioned by the doctors were allied HCWs, such as pharmacists and advanced practice nurses in PAD management. They not only boost doctors’ confidence in prescribing certain medications but also provide counselling and education to patients. In addition, pharmacists’ role in educating patients on why and how to take medications could contribute to a higher adherence rate in patients. Similarly, nurses can also play an important role in improving patients’ medication adherence by “counselling and highlighting the complications of the disease and the importance of medication adherence,” noted an internal medicine doctor (SCH-HCW-004)”.

Domain 6: Capacity for organisational change

Theme 8: Internal sharing to improve the prescription rate of EBMT on the departmental level

Some participants pointed out that the existence of various guidelines made it difficult for different HCWs to reach an agreement. “There are so many guidelines and depends on which one you follow. So, it’d be difficult to get everybody to agree on one,” noted a vascular surgeon (HCW-SGH-013). To increase the prescription rate, doctors suggested having internal teaching or publishing guidelines that “really differ a lot from what we are practising now” on the organisation’s intranet (HCW-SGH-001, nephrologist). They also suggested holding webinars to share vascular surgeons’ opinions on PAD management, and through knowledge sharing, to engage multidisciplinary teams in PAD management. Another suggestion they raised was to have quick access to the references, such as “little posters or reference cards or a QR code that we can have it on our phones or save somewhere that we can refer to,” as suggested by a radiologist (HCW-SGH-003).

Domain 7: Social, political and legal factors

Theme 9: Raise patients’ awareness of healthy behaviours in the community

One of the doctors pointed out that, despite several ongoing government campaigns, patients’ health awareness did not improve. To overcome this, more information, including healthy diets, should be broadcast in the community, and at source points such as coffee shops “to make people aware of things that they don’t know,” noted a radiologist (SGH-HCW-008). 


In this study, we applied the TICD framework to examine the current practices of EBMT use and factors for adherence and non-adherence to EBMT use in patients with PAD. We found that although most doctors were not familiar with updated PAD treatment guidelines, their practice was aligned with the recommended pharmacotherapy. We identified multiple barriers to implementing EBMT, and facilitators and strategies to improve EBMT adherence were also discussed.

At the healthcare provider level, a surprising finding was that most doctors were either not aware of any PAD guidelines or never searched for relevant guidelines. This result was similar to other studies that found inadequate awareness of clinical practice guidelines among practitioners in other disease areas.15,20 Several reasons led to the lack of awareness of guidelines. First, as PAD is one of the existing conditions, doctors’ usual practice is to continue patients’ existing medications without making changes. Second, due to the low referral threshold, doctors who did the initial assessment and referrals were not responsible for prescribing EBMT. Third, doctors believed that they were able to provide the treatment without guidelines, based on their expertise. Fourth, there was no regular internal education or sharing to make guidelines available to all the HCWs. The large gap in PAD guidelines awareness or familiarity highlights the need for effective internal education about the latest treatment guidelines and the need of developing easy-accessible reference tools.19

At the patient level, the most significant barrier to adhering to EBMT was inadequate knowledge of their medications. It has been widely accepted that medication knowledge plays a substantial role in medication adherence in patients with chronic diseases.21 Limited health literacy is a possible explanation for why many patients were not on antiplatelet therapy even though they had gone through several surgical interventions, a disappointing fact shared by a vascular surgeon who was interviewed. To tackle this problem, the doctors highlighted an urgent need to involve HCWs to educate them on the importance of taking medications.

At the system level, measures need to be taken to improve interprofessional collaboration. In the inpatient setting, patients with PAD and multiple comorbid conditions were admitted to the hospital for various reasons, while specialists tended to focus on one specific condition and failed to provide holistic care. Ironically, with too many doctors involved, no one was in charge of making decisions. One doctor pointed out that the lack of interprofessional communication led to the inadequate use of EBMT. A radiologist (SGH-HCW-003) said, “So sometimes, some patients don’t have like [sic] a regular doctor who knows them very well that it can get lost if there are too many doctors involved, none of them are communicating with each other.” Not knowing a patient’s history also resulted in doctors’ relying more on their expertise rather than the guidelines, which further limited EBMT use.20 This highlights the need to improve interprofessional communication by engaging a care manager to share regular updates of a patient and develop a comprehensive coordinated care plan.

This study had several limitations. First, our findings may have been affected by selection bias due to the low response rate of the HCWs, especially vascular surgeons, endocrinologists and cardiologists. However, our inclusion criteria made it possible that HCWs from departments that commonly interacted with PAD patients were included. Second, our findings may have been limited by the small sample size. However, this study fulfilled the requirement of having a sample size of at least 12 to reach data saturation.22,23 Third, the majority of the participants were not aware of PAD guidelines, resulting in limited insights into the barriers and facilitators to implementing the guidelines provided by them. However, our study was qualitative in nature, and we successfully explored patients’ perspectives on potential difficulties in taking medications through in-depth interviews.

The findings of this study will help build needed evidence for future interventions for improving guideline adherence in PAD management. The inefficiency in implementing EBMT in the current practice calls for actions to facilitate interprofessional communication and patient education. Future EBMT implementation may benefit from engaging specialists, primary care providers, and allied HCWs, and using a collaborative care approach plus focused training.


EBMT in PAD management remained underutilised and we identified several factors contributing to this. The key ones were HCWs’ lack of guideline awareness, frequent referrals, the limited generalisability of the guidelines to all patients, patients’ complicated conditions, patients’ limited understanding of their medications, cost, and short consultation time. Future interventions are needed to enhance EBMT utilisation in PAD management.

Supplentary Material. COREQ (COnsolidated criteria for REporting Qualitative research) checklist.


We would like to gratefully acknowledge all the contributions of investigators, clinical coordinators and participants. We would also like to acknowledge the grant support by the Academic Medicine (AM) – Health Services Research – HEARTS (HSR-HRT) Grant from SingHealth Duke-NUS Academic Medicine (AM/HRT007/2020).

Conflict of interest
The authors declared no conflicts of interest.


  1. Song P, Rudan D, Zhu Y, et al. Global, regional, and national prevalence and risk factors for peripheral artery disease in 2015: an updated systematic review and analysis. Lancet Glob Health 2019;7:e1020-e30.
  2. Fowkes FG, Rudan D, Rudan I, et al. Comparison of global estimates of prevalence and risk factors for peripheral artery disease in 2000 and 2010: a systematic review and analysis. Lancet 2013;382:1329-40.
  3. Subramaniam T, Nang EE, Lim SC, et al. Distribution of ankle–brachial index and the risk factors of peripheral artery disease in a multi-ethnic Asian population. Vasc Med 2011;16:87-95.
  4. Tan KW, Dickens BSL, Cook AR. Projected burden of type 2 diabetes mellitus-related complications in Singapore until 2050: a Bayesian evidence synthesis. BMJ Open Diabetes Res Care 2020;8.
  5. Morley RL, Sharma A, Horsch AD, et al. Peripheral artery disease. BMJ 2018;360:j5842.
  6. Flu HC, Tamsma JT, Lindeman JH, et al. A systematic review of implementation of established recommended secondary prevention measures in patients with PAOD. Eur J Vasc Endovasc Surg 2010;39:70-86.
  7. Campia U, Gerhard-Herman M, Piazza G, et al. Peripheral Artery Disease: Past, Present, and Future. Am J Med 2019;132:1133-41.
  8. Sobel M, Verhaeghe R. Antithrombotic therapy for peripheral artery occlusive disease: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition). Chest 2008;133:815S-43S.
  9. Aboyans V, Ricco JB, Bartelink MEL, et al. 2017 ESC Guidelines on the Diagnosis and Treatment of Peripheral Arterial Diseases, in collaboration with the European Society for Vascular Surgery (ESVS): Document covering atherosclerotic disease of extracranial carotid and vertebral, mesenteric, renal, upper and lower extremity arteries. Endorsed by: the European Stroke Organization (ESO) The Task Force for the Diagnosis and Treatment of Peripheral Arterial Diseases of the European Society of Cardiology (ESC) and of the European Society for Vascular Surgery (ESVS). Eur Heart J 2018;39:763-816.
  10. Gerhard-Herman MD, Gornik HL, Barrett C, et al. 2016 AHA/ACC Guideline on the Management of Patients With Lower Extremity Peripheral Artery Disease: Executive Summary: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines. Circulation 2017;135:e686-e725.
  11. Chan SL, Yap CJQ, Graves N, et al. Suboptimal adherence to medical therapy in patients undergoing lower limb angioplasty in Singapore. Ann Acad Med Singap 2023;52:216-8.
  12. Subherwal S, Patel MR, Kober L, et al. Missed opportunities: despite improvement in use of cardioprotective medications among patients with lower-extremity peripheral artery disease, underuse remains. Circulation 2012;126:1345-54.
  13. Renard BM, Seth M, Share D, et al. If not now, when? Prescription of evidence-based medical therapy prior to hospital discharge increases utilization at 6 months in patients with symptomatic peripheral artery disease. Vasc Med 2015;20:544-50.
  14. Stolfo D, Lund LH, Becher PM, et al. Use of evidence-based therapy in heart failure with reduced ejection fraction across age strata. Eur J Heart Fail 2022;24:1047-62.
  15. Tsang JL, Mendelsohn A, Tan MK, et al. Discordance between physicians’ estimation of patient cardiovascular risk and use of evidence-based medical therapy. Am J Cardiol 2008;102:1142-5.
  16. Banach M, Stulc T, Dent R, et al. Statin non-adherence and residual cardiovascular risk: There is need for substantial improvement. Int J Cardiol 2016;225:184-96.
  17. Schneider APH, Gaedke MA, Garcez A, et al. Effect of characteristics of pharmacotherapy on non-adherence in chronic cardiovascular disease: A systematic review and meta-analysis of observational studies. Int J Clin Pract 2018;72.
  18. Flottorp SA, Oxman AD, Krause J, et al. A checklist for identifying determinants of practice: a systematic review and synthesis of frameworks and taxonomies of factors that prevent or enable improvements in healthcare professional practice. Implement Sci 2013;8:35.
  19. Tong A, Sainsbury P, Craig J. Consolidated criteria for reporting qualitative research (COREQ): a 32-item checklist for interviews and focus groups. Int J Qual Health Care 2007;19:349-57.
  20. Weller CD, Richards C, Turnour L, et al. Barriers and enablers to the use of venous leg ulcer clinical practice guidelines in Australian primary care: A qualitative study using the theoretical domains framework. Int J Nurs Stud 2020;103:103503.
  21. Hyvert S, Yailian AL, Haesebaert J, et al. Association between health literacy and medication adherence in chronic diseases: a recent systematic review. Int J Clin Pharm 2023;45:38-51.
  22. Fugard AJB, Potts HWW. Supporting thinking on sample sizes for thematic analyses: a quantitative tool. Int J Soc Res Methodol 2015;18:669-84.
  23. Vasileiou K, Barnett J, Thorpe S, et al. Characterising and justifying sample size sufficiency in interview-based studies: systematic analysis of qualitative health research over a 15-year period. BMC Med Res Methodol 2018;18:148.