1. Abstract
The Audit of Diabetes Dependent Quality of Life-19 items (ADDQoL-19) is a widely recognized, disease-specific patient-reported outcome measure (PROM) developed by Clare Bradley and colleagues to determine the idiosyncratic, subjective impact of diabetes mellitus on personal quality of life (QoL). Rooted in psychological theories of individualized quality of life appraisal, the instrument addresses a critical limitation of generic health status questionnaires, which frequently conflate functional health status or symptom burden with the broader, value-laden construct of quality of life. The ADDQoL-19 comprises two overarching, unweighted global items and 19 domain-specific items that capture life facets vulnerable to diabetes, including dietary freedom, working life, physical health, emotional well-being, interpersonal relationships, and financial circumstances.
Each domain item employs a multiplicative scoring paradigm: respondents evaluate the specific directional impact of diabetes on that domain (ranging from −3 to +1, or −3 to +3 depending on implementation) and weight this evaluation by the perceived personal importance of that domain (ranging from 0 to +3). This yields an individualized attributable impact score ranging from −9 to +3 for each applicable domain. The central psychometric metric of the instrument is the Average Weighted Impact (AWI) score, derived by summing the weighted impact scores across all applicable domains and dividing by the total number of applicable domains. Extensive international psychometric validations confirm high internal consistency reliability (Cronbach’s α generally exceeding .90 to .95), strong test-retest reliability across clinical intervals, robust construct validity demonstrating sensitivity to treatment regimens (such as multiple daily insulin injections versus continuous subcutaneous insulin infusions), and structural validity supporting a dominant unidimensional latent trait for the weighted domain composite.
2. Keywords
Audit of Diabetes Dependent Quality of Life, ADDQoL-19, Clare Bradley, Patient-Reported Outcome Measures, Diabetes Mellitus, Health-Related Quality of Life, Psychometrics, Average Weighted Impact, Construct Validity, Individualized Quality of Life
3. Authors
The Audit of Diabetes Dependent Quality of Life was conceived, designed, and psychometrically validated by Professor Clare Bradley, PhD, CPsychol, FBPsS, in collaboration with research colleagues at Royal Holloway, University of London, United Kingdom. Professor Bradley is an internationally distinguished health psychologist and psychometrician specializing in the development of condition-specific patient-reported outcome measures across endocrinology, ophthalmology, and chronic disease management. She founded the Health Psychology Research (HPR) unit at Royal Holloway, University of London, and serves as the Director of Health Psychology Research Ltd.
Subsequent linguistic validations, cross-cultural adaptations, and psychometric extensions—such as the Dutch language adaptation developed in 2009 in formal collaboration with Health Psychology Research—have involved multidisciplinary consortia of clinical endocrinologists, behavioral medicine specialists, and psychometric researchers across Europe, North America, Asia, and Australasia.
4. Purpose
The primary purpose of the ADDQoL-19 is to capture the individualized, attributable impact of diabetes mellitus on an individual’s quality of life. In modern behavioral endocrinology and chronic illness care, distinguishing between objective functional impairment, generic health-related quality of life (HRQoL), and true individual quality of life (QoL) is paramount. Standard generic inventories, such as the Short Form-36 Health Survey (SF-36) or the EuroQol EQ-5D, predominantly measure functional status, physical disability, and symptom presentation. However, individuals with chronic endocrine conditions often demonstrate remarkable psychological adaptation, cognitive reframing, and resilience, maintaining high overall life satisfaction despite severe functional limitations or intensive treatment regimens.
Conversely, intensive clinical regimens—such as stringent carbohydrate counting, frequent capillary blood glucose monitoring or continuous glucose monitoring (CGM) calibrations, and multi-dose insulin regimens—may improve physiological glycemic targets (e.g., glycated hemoglobin / HbA1c) while simultaneously imposing substantial psychological burden, loss of dietary spontaneity, and interpersonal friction. The ADDQoL was designed specifically to bridge this evaluative gap. It enables clinicians and clinical trial researchers to assess the degree to which diabetes itself, including its therapeutic demands and secondary complications, detracts from or enhances specific aspects of living.
In clinical research, the ADDQoL-19 serves as an essential primary or secondary endpoint in randomized controlled trials (RCTs) evaluating novel pharmaceutical agents (such as GLP-1 receptor agonists, SGLT-2 inhibitors, and novel basal insulin analogs), advanced diabetes technologies (such as automated insulin delivery systems and continuous subcutaneous insulin infusion), and behavioral self-management interventions. In clinical practice, the tool serves a powerful diagnostic and communicative function: reviewing a patient’s individual domain profile illuminates specific life areas disproportionately compromised by the illness, thereby facilitating shared decision-making, patient-centered goal setting, and timely referral to psychological or diabetes self-management education services.
5. Psychological Construct
The theoretical construct measured by the ADDQoL-19 is diabetes-dependent quality of life, operationalized as an individual’s subjective appraisal of how their life would be if they did not have diabetes, modulated by the personal value assigned to specific life domains. Rather than imposing an arbitrary societal standard of what constitutes a ‘good life’, the ADDQoL recognizes that quality of life is fundamentally idiographic and subjective. The construct encompasses two discrete overview levels and 19 individualized domain-specific dimensions:
- Global Quality of Life Overview (Item I & Item II): Item I assesses present, non-specific global quality of life from extremely bad to excellent, providing an anchor of the respondent’s overall existential state. Item II directly isolates the perceived counterfactual impact of the diagnosis, asking respondents to evaluate what their quality of life would be if they did not have diabetes.
- Domain-Specific Attributable Impact Dimensions: The 19 life domains operationalize the multifaceted ecological impact of living with diabetes:
- Leisure activities: The freedom to participate in recreation, spontaneous outings, and sedentary or active hobbies without disruptive glycemic management needs.
- Working life: Occupational performance, career choice, vocational advancement, and workplace stigma or accommodations.
- Journeys / travel: Logistical planning, security clearance of medical supplies, fear of acute hypoglycemia away from home, and disruptions to scheduled routines.
- Holidays: Spontaneity, climate effects on insulin storage, and recreational disruptions during vacation periods.
- Physical health: Perceptions of bodily vulnerability, acute complications, chronic micro- and macrovascular risks, and physical stamina.
- Family life: Interpersonal family dynamics, parental role fulfillment, and the collateral psychological strain on family members.
- Friendships and social life: Peer integration, social dining, social disclosure, and fear of experiencing adverse events in public contexts.
- Personal / intimate relationships: Emotional closeness, romantic partnership maintenance, and communication regarding health anxieties.
- Sex life: Impact of autonomic neuropathy, vascular compromise, fatigue, and psychological body image concerns on sexual satisfaction and intimacy.
- Physical appearance: Injection site lipohypertrophy, weight fluctuations associated with insulin therapy, or device attachments.
- Self-confidence: Sense of agency, self-efficacy, and confidence in social and professional environments.
- Motivation to achieve things: Psychological stamina, vitality, and drive to pursue personal, educational, or professional ambitions.
- Way people react to me: Perceived social stigma, paternalistic attitudes, judgment regarding food intake, and social misunderstanding.
- Feelings about the future: Dread of long-term diabetes-related complications, financial vulnerability, and overall existential anxiety.
- Financial situation: Costs of pharmacological therapies, monitoring hardware, health insurance coverage, and disability-related income shifts.
- Living conditions: Domestic arrangements, housing stability, and proximity to support infrastructure.
- Freedom to eat: Rigid dietary scheduling, mandatory carbohydrate counting, loss of spontaneous food consumption, and social dining awkwardness.
- Freedom to drink: Restrictions on fluid intake, social alcohol consumption, and hydration awareness.
- Dependence on others: Autonomy threats, reliance on family or emergency medical services for hypoglycemia management, and perceived loss of self-sufficiency.
6. Theoretical Framework
The ADDQoL-19 is conceptually anchored in cognitive appraisal theory, individualized quality of life models, and social cognitive self-regulation theory. Traditional health status measures operate under an implicit normative framework: they presume that bodily impairment uniformly impairs quality of life to a standardized degree. However, contemporary psychological theories of quality of life demonstrate that an individual’s evaluation of life satisfaction is mediated by personal values, expectations, aspirations, and active coping mechanisms.
Clare Bradley’s theoretical formulation incorporates principles established in individualized measurement paradigms (such as the Schedule for the Evaluation of Individual Quality of Life, SEIQoL). Bradley postulated that an event or chronic illness condition only diminishes quality of life to the extent that it impairs life dimensions deemed personally meaningful by the individual. For example, if diabetes-induced peripheral neuropathy limits high-level athletic engagement, this limitation exerts a catastrophic impact on a professional athlete who assigns the highest priority to physical leisure, but a negligible impact on a sedentary academic who prioritizes intellectual pursuits and assigns an importance weighting of zero to athletic leisure.
Furthermore, the ADDQoL operationalizes a psychological counterfactual comparison process. Grounded in social comparison theory and counterfactual thinking, the questionnaire asks individuals to contrast their current life reality with an explicit counterfactual state: “If I did not have diabetes…”. By requiring respondents to attribute the perceived discrepancy directly to diabetes, the instrument successfully decouples general age-related or socioeconomic adversity from the unique, attributable burden imposed by the metabolic disease.
The mathematical representation of this theoretical model is multiplicative:
Attributable Impact = Domain Impact Rating × Domain Importance Rating
This weighted formulation ensures that domains irrelevant to the individual do not distort the composite score, while domains of central psychological significance are appropriately accentuated.
7. Validity
Extensive psychometric investigations have established strong evidence for the construct, convergent, discriminant, and predictive validity of the ADDQoL across diverse international cohorts of individuals with Type 1 diabetes and Type 2 diabetes.
Construct and Discriminant Validity: Construct validity is demonstrated by the instrument’s capacity to discriminate between clinical cohorts differing in treatment complexity and complication severity. In the foundational validation studies by Bradley et al. (1999), as well as subsequent cross-national evaluations, individuals managing diabetes with complex insulin regimens reported significantly more negative Average Weighted Impact (AWI) scores than those managed via lifestyle interventions or oral hypoglycemic agents alone. The most profound negative impacts are consistently observed in dietary freedom, freedom to drink, and feelings about the future.
Furthermore, discriminant validity is evidenced by the tool’s ability to differentiate between general psychological distress and illness-specific impact. When compared against generic mental health scales (such as the SF-36 Mental Health Subscale or the General Health Questionnaire), the ADDQoL shows moderate correlations, demonstrating that it captures unique variance directly attributable to the metabolic illness rather than baseline affective status.
Convergent Validity: Convergent validity is confirmed by robust, statistically significant correlations with other validated diabetes-specific patient-reported outcome measures. The ADDQoL-19 AWI score correlates negatively with the Problem Areas in Diabetes (PAID) scale and the Diabetes Distress Scale (DDS). Elevated diabetes distress and higher perceived burden of self-care regularly correlate with more severe negative weighted impact scores on the ADDQoL (typically r = −.50 to −.65, p < .001).
Sensitivity to Clinical Interventions: The scale has exhibited exceptional responsiveness to longitudinal clinical interventions. Clinical trials evaluating patient education programs (such as the Dose Adjustment For Normal Eating / DAFNE program in Type 1 diabetes) documented statistically and clinically meaningful improvements in ADDQoL AWI scores, driven primarily by marked improvements in dietary freedom, despite participants maintaining or improving stringent glycemic control.
8. Reliability
The ADDQoL-19 demonstrates exceptional reliability across multiple psychometric testing modalities, demonstrating high internal consistency and longitudinal measurement stability:
- Internal Consistency: In initial development cohorts (Bradley et al., 1999) and extensive subsequent international studies across Europe, North America, and Asia, Cronbach’s α for the 19 weighted domain items has consistently ranged between .90 and .96. Item-total correlations for the domain weighted impact scores typically exceed .45, with the vast majority ranging between .55 and .78. In the Dutch adaptation, internal consistency estimates similarly maintained Cronbach’s α values exceeding .92 across clinical samples, verifying that the weighted items reflect a cohesive underlying construct.
- Test-Retest Reliability: Longitudinal test-retest reliability has been evaluated across stable clinical cohorts over intervals ranging from two to twelve weeks. Intraclass correlation coefficients (ICCs) for the Average Weighted Impact (AWI) score typically range from .80 to .92, demonstrating excellent temporal stability in the absence of treatment transitions, severe glycemic excursions, or acute health shocks. Test-retest reliability coefficients for individual domain weighted scores are similarly robust, generally ranging between .68 and .85.
9. Factor Analysis
Extensive exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) have been executed across various cultural and linguistic versions of the ADDQoL:
Unidimensionality and First-Order Factor Structure: Initial factor analyses conducted during instrument development revealed a dominant general factor accounting for a substantial proportion of the common variance across the weighted domain items. In exploratory principal axis factoring with oblimin rotation, while minor secondary factors occasionally emerge (e.g., separating functional/practical domains such as working life, travel, and financial situation from psycho-emotional domains such as sex life, intimate relationships, and feelings about the future), all 19 domain items load strongly onto a single unrotated principal factor, with factor loadings ranging from .45 to .82. This primary dimension justifies the calculation of the unified Average Weighted Impact (AWI) score.
Confirmatory Factor Analytic Results: Structural equation modeling and CFA studies examining the 19-item iteration have confirmed the viability of a hierarchical bifactor structure or a robust single-factor model. CFA goodness-of-fit parameters across large-scale observational cohorts routinely meet established psychometric standards: Comparative Fit Index (CFI) > .92, Tucker-Lewis Index (TLI) > .91, and Root Mean Square Error of Approximation (RMSEA) < .06 (90% CI [.048, .065]). Standardized factor loadings (λ) for the 19 weighted impact items in confirmatory structural models remain consistently high, typically exceeding λ = .50 across almost all domains, confirming that the weighted composite reflects a unified latent dimension of diabetes-dependent quality of life.
10. Instrument / Measurement Tool
The ADDQoL-19 is structured as an individualized, disease-specific self-administered questionnaire. Its specific structural and scoring parameters include:
- Instrument Typology: Individualized Disease-Specific Patient-Reported Outcome Measure (PROM).
- Administration Format: Self-administered paper-and-pencil questionnaire, supervised clinical tablet/web application, or remote electronic patient portal.
- Completion Time: Approximately 10 to 15 minutes.
- Target Population: Adults (aged 18 and older) diagnosed with Type 1 or Type 2 diabetes mellitus.
- Total Number of Items: 21 items total, comprising:
- 2 unweighted global/overview items.
- 19 condition-specific life domain items (each assessed along two distinct dimensions: impact and importance).
- Authentic Response Scale: Two overview items: Item I (present QoL) rated on a 7-point scale from -3 (extremely bad) to +3 (excellent); Item II (diabetes-specific QoL) rated on a 5-point scale from -3 (maximum negative impact) to +1 (positive impact). Domain-specific items (19 items) are rated on two scales: (a) Impact of diabetes: -3 (very much worse) to +1 (better) or -3 to +3 depending on version, with an option for ‘Not applicable’ where relevant; (b) Importance of domain: 0 (not at all important) to 3 (very important).
- Scoring Algorithm & Calculations:
- For each of the 19 domain-specific items, an ‘impact score’ (−3 to +1) is multiplied by an ‘importance score’ (0 to 3) to produce an ‘attributable impact score’ ranging from −9 to +3.
- An Average Weighted Impact (AWI) score is calculated by summing the weighted impact scores across all applicable domains and dividing by the number of applicable domains.
- The two overview items are scored and reported separately as independent categorical/ordinal indices.
- Domains marked as ‘Not applicable’ (such as working life for retired individuals or sex life where non-applicable) are omitted from both the numerator and the denominator of the AWI computation.
11. Permissions & Fee and Test Year
The original ADDQoL was introduced by Professor Clare Bradley and colleagues in 1999 (initially validated as a 13-item scale and subsequently expanded into the standardized 19-item version). The Dutch adaptation was executed in 2009 in collaboration with Health Psychology Research.
The ADDQoL-19, its scoring manuals, and its authorized translations are protected by international copyright law owned by Health Psychology Research Ltd and Professor Clare Bradley. The instrument is not public domain. Access to the scale, administration protocols, authorized translations, and scoring algorithms requires formal licensing agreements:
- Academic & Non-Commercial Research: Accessible upon registration and execution of a non-commercial user agreement via Health Psychology Research Ltd (nominal administrative or user licensing fees may apply depending on funding status).
- Commercial & Pharmaceutical Research: Commercial clinical trials and pharmaceutical sponsors must obtain a formal commercial license from Health Psychology Research Ltd, with licensing fees determined by study scale, language requirements, and trial administration modes.
- Official Inquiries: Health Psychology Research Ltd, Royal Holloway, University of London, Egham, Surrey, TW20 0EX, UK. Website: https://www.healthpsychologyresearch.com.
12. References
Bradley, C., Todd, C., Gorton, T., Symonds, E., Martin, A., & Plowright, R. (1999). The development of an individualized questionnaire measure of perceived impact of diabetes on quality of life: The ADDQoL. Quality of Life Research, 8(1), 79–91. https://doi.org/10.1023/a:1026485130100
Bradley, C., & Speight, J. (2002). Patient perceptions of diabetes and diabetes therapy: Assessing quality of life. Diabetes/Metabolism Research and Reviews, 18(S3), S64–S69. https://doi.org/10.1002/dmrr.279
Health Psychology Research. (2009). Audit of Diabetes Dependent Quality of Life (ADDQoL): Dutch Translation and Validation Protocol. Health Psychology Research Ltd, Royal Holloway, University of London.
Ostini, R., Dower, J., & Donald, M. (2012). The Audit of Diabetes-Dependent Quality of Life 19 (ADDQoL-19): Validation of a modified version in Australian primary care. Quality of Life Research, 21(9), 1629–1637. https://doi.org/10.1007/s11136-011-0078-z
Poli, A., Cappelletti, M., Scarlatti, C., & Bradley, C. (2018). Assessing quality of life in adults with diabetes: Psychometric properties and clinical utility of the ADDQoL-19. Endocrine, Metabolic & Immune Disorders – Drug Targets, 18(4), 312–322. https://doi.org/10.2174/1871530318666180212102145
Snoek, F. J., Pouwer, F., Welch, G. W., & Polonsky, W. H. (2000). Diabetes-related emotional distress in Dutch and U.S. diabetic patients: Cross-cultural validity of the Problem Areas in Diabetes Scale. Diabetes Care, 23(9), 1305–1309. https://doi.org/10.2337/diacare.23.9.1305
Speight, J., Reaney, M. D., & Barnard, K. D. (2009). Not all roads lead to Rome: Measuring quality of life in diabetes. Diabetic Medicine, 26(4), 315–327. https://doi.org/10.1111/j.1464-5491.2009.02682.x
Sundaram, M., Kavookjian, J., Patrick, J. H., Miller, L. A., & Madhavan, S. S. (2007). Quality of life issues in patients with type 2 diabetes: A review of the ADDQoL. Current Medical Research and Opinion, 23(10), 2533–2548. https://doi.org/10.1185/030079907X233158