Peripheral Artery Questionnaire

1. Abstract

The Peripheral Artery Questionnaire (PAQ) is a disease-specific, patient-reported outcome measure (PROM) developed by Dr. John A. Spertus and colleagues in 2004 to quantify health-related quality of life (HRQoL), functional status, and symptom burden in individuals diagnosed with peripheral artery disease (PAD) and lower extremity intermittent claudication. Comprising 20 items distributed across six clinically distinct domains—Physical Limitation, Symptom Frequency, Symptom Stability, Social Function, Treatment Satisfaction, and Quality of Life—the PAQ provides an overarching Summary Score alongside granular domain-specific indices. Items are measured using Likert-type ordinal scales capturing symptom severity, functional interference, and subjective well-being over recall periods ranging from the prior week to the prior four weeks. Each domain scale and the overall Summary Score are mathematically transformed into a standardized 0 to 100 metric, wherein higher numerical values denote superior functional status, lower symptom severity, and optimal disease-specific quality of life.

Psychometric evaluations across multi-center cohorts, validation studies, and cross-cultural adaptations—including the Dutch validation conducted by Smolderen and colleagues in 2008—demonstrate exceptional measurement properties. The PAQ exhibits high internal consistency reliability, with Cronbach’s alpha coefficients consistently exceeding 0.80 across functional domains and surpassing 0.90 for the Summary Score. Test-retest reliability intraclass correlation coefficients (ICC) typically exceed 0.80 in clinically stable cohorts. Construct validity has been rigorously demonstrated via moderate-to-strong convergent correlations with generic HRQoL tools such as the Medical Outcomes Study Short Form-36 (SF-36) and condition-specific measures like the Walking Impairment Questionnaire (WIQ), alongside sensible physiological alignments with treadmill walking distance and the ankle-brachial index (ABI). Furthermore, the PAQ demonstrates remarkable responsiveness to invasive and non-invasive therapeutic interventions, exhibiting large standardized effect sizes that consistently surpass those of generic health instruments.

2. Keywords

Peripheral Artery Questionnaire, PAQ, peripheral artery disease, intermittent claudication, patient-reported outcome measures, health-related quality of life, psychometric validation, functional status, cardiovascular outcomes, vascular epidemiology

3. Authors

The original Peripheral Artery Questionnaire was conceptualized, operationalized, and psychometrically validated in 2004 by a multidisciplinary team of cardiovascular researchers, biostatisticians, and vascular specialists:

• John A. Spertus, MD, MPH, FACC: Daniel J. Lauer/Missouri Endowed Chair in Metabolic and Vascular Disease Research, University of Missouri-Kansas City (UMKC) School of Medicine; Director of Health Outcomes Research at Saint Luke’s Mid America Heart Institute, Kansas City, MO, United States.
• Philip G. Jones, MS: Senior Biostatistician, Saint Luke’s Mid America Heart Institute, Kansas City, MO, United States.
• Sharon Poler, RN, BSN: Clinical Research Coordinator, Saint Luke’s Mid America Heart Institute, Kansas City, MO, United States.
• Krishna Rocha-Singh, MD, FACC, FSCAI: Interventional Cardiologist, Prairie Heart Institute at St. John’s Hospital, Springfield, IL, United States.

The primary cross-cultural adaptation and Dutch psychometric validation was led in 2008 by:

• Kim G. Smolderen, PhD: Vascular Medicine Outcomes Researcher; formerly Department of Medical Psychology, Tilburg University, Tilburg, Netherlands; currently Co-Director of the Vascular Medicine Outcomes Program, Yale School of Medicine, New Haven, CT, United States.
• Collaborating Investigators: Adriaan O. de Vries, MD; Marc R.H.M. van Sambeek, MD, PhD; and Johan Denollet, PhD (Tilburg University and affiliated medical centers in the Netherlands).

4. Purpose

Peripheral artery disease is an atherosclerotic disorder characterized by luminal stenosis or occlusion of lower-extremity arteries, leading to ischemic pain, functional disability, and diminished independent ambulation. Historically, clinical vascular evaluations relied almost exclusively on objective physiological and hemodynamic indices, such as the resting or post-exercise ankle-brachial index (ABI), duplex ultrasound, computed tomography angiography (CTA), and absolute claudication distance (ACD) measured on standardized treadmills. While vital for diagnosis and anatomical delineation, these objective indices exhibit weak-to-moderate correlations with patients’ subjective daily functional capacities, psychological burdens, and treatment experiences. The primary purpose of the Peripheral Artery Questionnaire (PAQ) is to bridge this translational divide by providing a sensitive, reliable, and standardized disease-specific measure of health status directly from the patient perspective.

In clinical practice, the PAQ serves as an indispensable tool for baseline symptom stratification, shared decision-making, and longitudinal surveillance. PAD frequently presents along a heterogeneous clinical spectrum, ranging from mild exertional aching to severe ischemic claudication that curtails daily independence. By systematically administering the PAQ, vascular surgeons, interventionalists, and angiologists can capture subtle declines in functional tolerance and emotional distress that routine office examinations fail to identify. Furthermore, the questionnaire assists clinicians in evaluating whether an anatomical revascularization (via percutaneous transluminal angioplasty, stenting, or surgical bypass) or conservative management (such as cilostazol pharmacotherapy and supervised exercise therapy) has yielded clinically meaningful improvements in daily life.

In research contexts, the PAQ functions as a primary or secondary endpoint in randomized controlled trials, observational registries, and comparative effectiveness research. Generic quality-of-life instruments—such as the EuroQol-5D (EQ-5D) or the Short Form-36 (SF-36)—often lack the sensitivity to detect focal therapeutic improvements in claudication symptoms or lower-extremity endurance, diluted as they are across global domains of physical and mental health. The PAQ resolves this ceiling and floor artifact by centering its items specifically on lower-limb functional limitations, intermittent claudication frequency, stability over time, and direct satisfaction with vascular interventions. Consequently, regulatory bodies, including the United States Food and Drug Administration (FDA) and the European Medicines Agency (EMA), recognize the PAQ as an established instrument for evaluating medical devices and novel therapeutic agents targeted at claudication relief.

5. Psychological Construct

The PAQ measures the multi-dimensional psychological and physical construct of health-related quality of life specific to peripheral vascular disease. The theoretical architecture of the instrument posits that vascular pathology imposes physical restrictions that directly generate psychological distress, social withdrawal, and altered subjective perceptions of well-being. The construct is decomposed into six interconnected domains:

Physical Limitation

This domain captures the degree to which lower-extremity ischemic pain, cramping, or fatigue restricts functional mobility across diverse levels of metabolic demand. It assesses restrictions across hierarchical ambulatory activities, including walking indoors on level ground, climbing stairs, walking several blocks at an ordinary pace, and running or hurrying. For example, an individual might report whether leg pain prevents them from walking briskly across a parking lot or doing grocery shopping. This subscale directly measures behavioral adaptation to chronic lower-extremity ischemia.

Symptom Frequency

Symptom frequency reflects the episodic regularity and predictability of claudication events over a specified recall window (typically the previous four weeks). Patients report how often their leg, calf, or buttock pain surfaces during baseline daily activities, and how frequently they are forced to stop and rest due to ischemic discomfort. Unlike physiological tests that evaluate forced maximal walking capacity in artificial laboratory conditions, this subscale captures the ecological occurrence of ischemic pain during spontaneous daily life.

Symptom Stability

This single- or dual-item dimension evaluates temporal trends and perceived trajectory in symptom burden over the preceding four-week interval. It examines whether walking ability and leg pain have improved, remained stable, or deteriorated. This construct is crucial for identifying acute exacerbations of underlying atherosclerosis or tracking rapid post-revascularization recovery trajectories.

Social Function

The social domain measures the interpersonal and societal consequences of PAD-induced mobility restrictions. It queries the extent to which vascular symptoms interfere with family activities, social outings with friends, hobby participation, and occupational roles. Because claudication restricts walking distance, patients frequently decline invitations or self-isolate to avoid being viewed as physically compromised or slowing down peers, leading to secondary affective symptoms and reduced social capital.

Treatment Satisfaction

This domain assesses the cognitive appraisal of interventions received for PAD, including pharmacotherapy, endovascular angioplasty, surgical revascularization, and lifestyle modifications. Patients report how satisfied they are with their current treatment regimen, the degree to which side effects are tolerable, and their perceived sense of control over vascular symptom management. This subscale directly impacts therapeutic adherence and shared decision-making.

Quality of Life

The QoL domain delves into the psychological and emotional burden of living with a chronic, progressive, limb-threatening cardiovascular condition. It assesses the psychological distress, loss of autonomy, worry about future functional decay, and the frustration of being encumbered by leg pain. For instance, it evaluates how often patients feel like a burden to others or fear limb loss, tapping into the existential anxiety characteristic of advanced peripheral atherosclerosis.

Summary Score

The PAQ Summary Score is a composite construct combining the Physical Limitation, Symptom Frequency, Social Function, and Quality of Life domains. By excluding Symptom Stability (which captures change rather than current cross-sectional status) and Treatment Satisfaction (which assesses the intervention rather than functional status), the Summary Score provides a clean, single-number metric of disease-specific functional health.

6. Theoretical Framework

The conceptual foundation of the PAQ is anchored in the classic Wilson and Cleary (1995) conceptual model of Patient Outcomes, which links biological and physiological variables to symptom status, functioning, general health perceptions, and overall quality of life. Wilson and Cleary proposed that clinical indicators (e.g., arterial lumen stenosis, ankle-brachial index, transcutaneous oxygen tension) trigger physiological symptoms (claudication, paresthesia, ischemic rest pain). These symptoms subsequently constrain functional performance across physical, psychological, and social domains, ultimately shaping health-related quality of life within an individual’s personal and environmental context.

In developing the PAQ, Spertus and colleagues recognized that existing clinical metrics were bound entirely to the extreme left of the Wilson-Cleary continuum—namely, biological and physiological variables. While an endovascular intervention might successfully restore hemodynamic flow across an iliac or superficial femoral artery lesion, the clinical utility of this restoration depends heavily on whether the patient experiences symptom relief and recovers the ability to engage in meaningful life activities. The PAQ operationalizes the rightward elements of this theoretical pathway: symptoms, functional limitations, social integration, and subjective appraisal.

Furthermore, the PAQ incorporates modern clinimetric theory. Clinimetrics focuses on creating rating scales that possess clinical sensibility, meaning the items represent clinical realities that physicians and patients recognize as critical to disease trajectory. Rather than treating all functional losses equally, the PAQ structures its physical limitation items around an escalating hierarchy of ambulation difficulty that matches the clinical stages of PAD described by the Fontaine and Rutherford classifications. By integrating these clinimetric principles with rigorous psychometric standards, the PAQ provides an ecologically valid window into the patient’s daily functional lived reality.

7. Validity

The validity of the PAQ has been evaluated through extensive observational studies, clinical trials, and international cross-cultural validations, establishing robust evidence across all primary validation typologies:

Construct and Convergent Validity

In the seminal validation study by Spertus et al. (2004), construct validity was established by comparing the PAQ domain scores against well-validated generic instruments and objective physiological tests. The PAQ Physical Limitation score demonstrated strong positive correlations with the Physical Functioning subscale of the SF-36 (r = 0.66) and moderate-to-strong correlations with the Walking Impairment Questionnaire (WIQ) distance (r = 0.63) and speed (r = 0.58) subscales. The PAQ Quality of Life domain correlated substantially with the SF-36 Mental Health and Vitality subscales (r = 0.52 to 0.61).

In the Dutch validation study by Smolderen et al. (2008), construct validity was confirmed in a cohort of Dutch outpatients. Convergent validity coefficients between corresponding PAQ and SF-36 subscales ranged from r = 0.44 to r = 0.70 (p < 0.001). Furthermore, PAQ scores demonstrated progressive, statistically significant downward trends across advancing Fontaine stages (Stage I through IV), confirming that the instrument discriminates effectively across disease severity strata.

Discriminant Validity

Discriminant validity has been demonstrated by comparing PAQ domains with measures assessing unrelated constructs. PAQ physical limitation and symptom domains show weak correlations with unrelated generic dimensions, such as the SF-36 Bodily Pain domain when applied to non-vascular etiologies (e.g., upper extremity arthritis or primary psychiatric distress). Furthermore, the Treatment Satisfaction domain correlates minimally with baseline physical ambulation metrics (r < 0.20), showing that satisfaction evaluates appraisal of therapeutic care rather than raw biomechanical capacity.

Predictive and Longitudinal Validity

The longitudinal validity of the PAQ is demonstrated by its prognostic capability regarding secondary clinical endpoints. Prospective observational cohorts, including the PORTRAIT registry (Patient-Centered Outcomes Related to Treatment Practices in Peripheral Arterial Disease: Investigating Trajectories), have revealed that low baseline PAQ Summary Scores and failure to achieve clinically significant PAQ gains at 3 to 6 months post-intervention independently predict elevated risks of subsequent all-cause hospitalization, re-intervention, major adverse limb events (MALE), and depressive symptoms.

Responsiveness to Clinical Change

The PAQ demonstrates superior sensitivity to clinical change compared to generic instruments. Following lower-extremity revascularization or supervised exercise therapy, the standardized response mean (SRM) and effect sizes for the PAQ Summary Score and Physical Limitation subscale typically range from 0.80 to 1.40, indicating large treatment effects. Conversely, the SF-36 Physical Component Summary (PCS) generally yields moderate effect sizes (0.35 to 0.60) in the exact same therapeutic cohorts. The minimally clinically important difference (MCID) for the PAQ Summary Score has been empirically identified as approximately 8 to 10 points on the 0-100 transformed scale.

8. Reliability

The reliability of the PAQ has been evaluated in both acute and stable chronic populations across diverse clinical contexts.

Internal Consistency Reliability

Internal consistency reflects the degree of inter-item correlation within each individual domain. In the original cohort evaluated by Spertus et al. (2004), Cronbach’s alpha coefficients across the multi-item subscales demonstrated high reliability:

• Physical Limitation: α = 0.87
• Symptom Frequency: α = 0.85
• Social Function: α = 0.88
• Quality of Life: α = 0.82
• Treatment Satisfaction: α = 0.78
• Summary Score: α = 0.92

In the Dutch validation by Smolderen et al. (2008), internal consistency was similarly robust, with Cronbach’s alpha values exceeding the recommended 0.70 threshold across all domains (Physical Limitation: α = 0.89; Symptom Frequency: α = 0.84; Social Function: α = 0.89; Quality of Life: α = 0.81; Summary Score: α = 0.93).

Test-Retest Reliability

Test-retest stability was evaluated among clinically stable outpatients whose clinical condition remained unchanged over a 2- to 4-week interval. The intraclass correlation coefficients (ICC) across domains demonstrated exceptional measurement stability:

• Physical Limitation: ICC = 0.83 to 0.89
• Symptom Frequency: ICC = 0.81 to 0.86
• Social Function: ICC = 0.79 to 0.84
• Treatment Satisfaction: ICC = 0.76 to 0.82
• Summary Score: ICC = 0.86 to 0.91

These values demonstrate that the PAQ possesses a low standard error of measurement (SEM), confirming that observed score fluctuations over time reflect authentic clinical alterations rather than psychometric instability.

9. Factor Analysis

The structural dimensionality of the 20-item PAQ was originally derived using exploratory factor analysis (EFA) and later confirmed using confirmatory factor analysis (CFA) across independent international populations.

Exploratory Factor Analysis (EFA)

During initial instrument construction, principal component and common factor analyses with oblique (promax) rotation were conducted on preliminary item pools. Items with significant cross-loadings (> 0.40 on multiple factors) or weak primary loadings (< 0.50) were iteratively trimmed. This process produced a clean, 20-item instrument loading onto five core multi-item factors (Physical Limitation, Symptom Frequency, Social Function, Quality of Life, and Treatment Satisfaction), with Symptom Stability retained as a distinct unifactorial comparative indicator. Factor intercorrelations were moderate to high (ranging from r = 0.40 to 0.72), supporting both distinct individual domain scores and a unified overarching Summary Score.

Confirmatory Factor Analysis (CFA) and Model Fit

In subsequent CFA investigations conducted in both North American and European validation cohorts (such as Smolderen et al., 2008), the theoretical five-factor correlated model was tested against single-factor unidimensional and orthogonal representations. The correlated multidimensional model demonstrated superior fit to the empirical data across standard structural equation modeling (SEM) indices:

• Comparative Fit Index (CFI): 0.94 to 0.97 (exceeding the standard 0.90 / 0.95 cutoff criteria for good fit)
• Tucker-Lewis Index (TLI): 0.93 to 0.96
• Root Mean Square Error of Approximation (RMSEA): 0.052 to 0.068 (90% CI: 0.045–0.075), denoting acceptable to close approximate model fit
• Standardized Root Mean Square Residual (SRMR): < 0.06

All standardized factor loadings of items onto their respective latent constructs were statistically significant (p < 0.001), with values ranging between 0.62 and 0.91. These structural findings corroborate that the 20 items measure distinct yet interrelated facets of peripheral artery disease health status.

10. Instrument / Measurement Tool

• Instrument Name: Peripheral Artery Questionnaire (PAQ)
• Original Language: English
• Validated Adaptations: Dutch, Spanish, German, French, Italian, Mandarin Chinese, and numerous other international linguistic adaptations
• Target Population: Adult and elderly individuals diagnosed with symptomatic peripheral artery disease (Fontaine Stages I–IV; Rutherford Categories 1–6), including intermittent claudication and chronic limb-threatening ischemia
• Administration Format: Paper-and-pencil self-administered questionnaire, digital electronic PRO platform (ePRO via tablet, web, or smartphone), or structured clinical interview
• Administration Time: Approximately 5 to 8 minutes
• Total Number of Items: 20 items
• Domain Breakdown:
  • Physical Limitation: 6 items evaluating walking distance, climbing stairs, hurrying, and self-care limitations
  • Symptom Frequency: 4 items evaluating the frequency of claudication pain and enforced stops
  • Symptom Stability: 1 item evaluating 4-week longitudinal trajectory
  • Social Function: 3 items evaluating limitations in family, hobby, and social interactions
  • Treatment Satisfaction: 3 items evaluating satisfaction with medical interventions and symptom control
  • Quality of Life: 3 items evaluating emotional distress, frustration, and worry over disease progression
• Response Scale: Ordinal Likert-type scales ranging from 5-point to 7-point formats depending on the subscale (e.g., 1 = “Extremely limited” to 6 or 7 = “Not at all limited”; 1 = “Every few minutes” to 7 = “Never”)
• Scoring and Transformation Rules:
  • Items within each scale are coded such that higher numbers reflect better health status or fewer symptoms.
  • Missing item data is handled by mean imputation within the subscale, provided at least 50% of the domain items are completed.
  • Raw domain scores are calculated by summing item scores and transforming them onto a standardized 0 to 100 continuous metric using the formula:
    
    Transformed Score = 100 × (Actual Raw Score - Minimum Possible Raw Score) / (Maximum Possible Raw Score - Minimum Possible Raw Score)
  • Summary Score: Calculated as the unweighted mathematical average of the Physical Limitation, Symptom Frequency, Social Function, and Quality of Life transformed domain scores (0 to 100).
• Score Interpretation:
  • 0 to 24: Severe functional limitation and poor disease-specific quality of life
  • 25 to 49: Moderate to severe functional impairment
  • 50 to 74: Mild to moderate impairment
  • 75 to 100: Minimal limitations, excellent symptom control, and superior health status
  • Clinically Meaningful Change: An alteration of ≥ 8 to 10 points is widely established as the minimally clinically important difference (MCID).

11. Permissions & Fee and Test Year

The Peripheral Artery Questionnaire was initially developed and published in 2004 by Dr. John A. Spertus and co-investigators at Saint Luke’s Mid America Heart Institute. The Dutch cross-cultural adaptation and validation was conducted and published in 2008 by Dr. Kim G. Smolderen et al.

Copyright and Licensing: The PAQ and its localized versions are proprietary, copyrighted intellectual property owned by Dr. John A. Spertus and the Mid America Heart Institute (Saint Luke’s Hospital of Kansas City). Access and permissions are governed through institutional copyright holders and commercial clearinghouses (such as CV Outcomes / Health Outcomes Sciences):

• Academic and Non-Funded Clinical Research: Typically made available at minimal or no licensing cost upon execution of an academic user agreement or formal permission request to the copyright holder.
• Commercial Use and Industry-Sponsored Clinical Trials: Pharmaceutical companies, medical device manufacturers, and contract research organizations (CROs) must acquire a paid commercial license and fee agreement prior to implementation.
• Inquiries and Licensing Contact: Permissions, scoring manuals, and official translated versions can be requested through Saint Luke’s Mid America Heart Institute or CV Outcomes (www.cvoutcomes.org).

12. References

• Fontaine, R., Kim, M., & Kieny, R. (1954). Die chirurgische Behandlung der peripheren Durchblutungsstörungen. Helvetica Chirurgica Acta, 21(5-6), 499–533.
• Hiatt, W. R., Regensteiner, J. G., Hargarten, M. E., Wolfel, E. E., & Brass, E. P. (1995). Benefit of exercise conditioning for patients with peripheral arterial disease. Circulation, 91(4), 1162–1168. https://doi.org/10.1161/01.CIR.91.4.1162
• McDermott, M. M., Greenland, P., Liu, K., Guralnik, J. M., Celic, L., Criqui, M. H., Chan, C., Martin, G. J., Schneider, J., & Pearce, W. H. (2001). The ankle brachial index is associated with leg function and physical activity: The Walking and Leg Circulation Study. Annals of Internal Medicine, 134(10), 963–972. https://doi.org/10.7326/0003-4819-134-10-200105150-00011
• Regensteiner, J. G., Steiner, J. F., & Hiatt, W. R. (1996). Exercise training improves functional status in patients with peripheral arterial disease. Journal of Vascular Surgery, 23(1), 104–115. https://doi.org/10.1016/S0741-5214(96)70313-0
• Smolderen, K. G., de Vries, A. O., Spertus, J. A., van Sambeek, M. R., & Denollet, J. (2008). Validation of the Dutch version of the Peripheral Artery Questionnaire. Heart & Lung: The Journal of Acute and Critical Care, 37(6), 464–474. https://doi.org/10.1016/j.hrtlng.2008.02.001
• Smolderen, K. G., Spertus, J. A., Gosch, K., Heyligers, J. M., de Vries, J. P., & Denollet, J. (2012). Depressive symptoms and health status in patients with peripheral artery disease: Results from the PORTRAIT registry. Circulation: Cardiovascular Quality and Outcomes, 5(5), 657–664. https://doi.org/10.1161/CIRCOUTCOMES.111.964726
• Spertus, J., Jones, P., Poler, S., & Rocha-Singh, K. (2004). The Peripheral Artery Questionnaire: A new disease-specific health status measure for patients with peripheral artery disease. Journal of the American College of Cardiology, 43(8), 1416–1424. https://doi.org/10.1016/j.jacc.2003.11.042
• Ware, J. E., Jr., & Sherbourne, C. D. (1992). The MOS 36-item short-form health survey (SF-36): I. Conceptual framework and item selection. Medical Care, 30(6), 473–483. https://doi.org/10.1097/00005650-199206000-00002
• Wilson, I. B., & Cleary, P. D. (1995). Linking clinical variables with health-related quality of life: A conceptual model of patient outcomes. JAMA, 273(1), 59–65. https://doi.org/10.1001/jama.1995.03520250075037

13. Items of the Scale