Quality of Life Index (QLI)

Abstract

The Quality of Life Index (QLI) is a comprehensive and multidimensional psychological scale designed to measure an individual’s subjective Quality of Life (QoL). Developed by Carol Estwing Ferrans and Mary Powers, the QLI is unique in its structure, requiring respondents to evaluate 33 domains of life using two distinct measures: satisfaction with the domain (Part I) and the importance assigned to that domain (Part II). This dual assessment allows for the calculation of a weighted QoL score, where satisfaction in areas deemed highly important contributes more significantly to the overall index. The instrument is divided into four main subscales: Health and Functioning, Social and Economic, Psychological/Spiritual, and Family, making it highly valuable for clinical and health outcomes research.

Keywords

Quality of Life Index, QLI, Quality of Life, QoL assessment, Ferrans and Powers, subjective well-being, satisfaction, importance, life domains, psychometrics.

Authors

Carol Estwing Ferrans, Mary Powers.

Purpose

The primary purpose of the Quality of Life Index (QLI) is to provide a robust and individualized assessment of subjective well-being across various life domains. The scale was developed to overcome limitations found in earlier measures by recognizing that overall QoL is not simply the sum of satisfactions, but rather a weighted average based on personal values. By measuring both satisfaction and importance, the QLI provides a score that reflects the congruence between an individual’s lived experience and their personal priorities.

This instrument is widely used in health research, particularly for evaluating the effectiveness of medical treatments, tracking changes in QoL among patients with chronic conditions (such as cancer), and comparing the perceived well-being of diverse populations. Its structure allows clinicians and researchers to identify specific life areas where intervention or support might be most beneficial.

Construct

The QLI measures the construct of Quality of Life, which is conceptualized here as a subjective, multidimensional state influenced by personal values. The core theoretical model underlying the QLI posits that QoL is defined by the degree to which an individual is satisfied with aspects of life that they consider important. If a person is highly satisfied with an aspect they consider unimportant, that satisfaction contributes less to the overall QoL score than satisfaction in a highly important domain.

The 33 items are categorized into four conceptually distinct subscales: Health and Functioning, Social and Economic, Psychological/Spiritual, and Family. This structure ensures comprehensive coverage of the physical, mental, social, and existential components essential to a holistic definition of the QoL construct.

Validity

The validity of the QLI has been established through numerous psychometric properties studies since its initial publication. Initial research demonstrated strong construct validity, showing that the instrument accurately measures the hypothesized domains and that the resulting weighted scores correlate logically with other established measures of health status and psychological distress. The two-part structure (satisfaction and importance) is central to its theoretical validity.

Furthermore, the QLI exhibits strong discriminant validity, successfully differentiating between patient groups with known differences in health and functional status. The scale’s adaptability has also been confirmed through validations in specific clinical populations (e.g., oncology patients) and across various cultural and linguistic groups, reinforcing its general applicability in QoL assessment.

Reliability

The QLI demonstrates high levels of internal consistency reliability, indicating that items within each subscale are measuring the same underlying construct. Cronbach’s alpha coefficients for the total scale and its subscales are consistently reported in the acceptable to excellent range in various populations and language adaptations, suggesting high homogeneity of the items.

In addition to strong internal consistency, test-retest reliability studies confirm the stability of the QLI scores over time, assuming the individual’s underlying health status and life circumstances remain relatively constant. This makes the instrument reliable for repeated measurements in longitudinal studies to monitor changes in subjective well-being.

Factor Analysis

Factor analysis performed during the development and refinement of the QLI confirmed the existence of four primary factors, which correspond to the scale’s subscales. This factor structure provides strong empirical support for the theoretical model that QoL is composed of distinct, yet interrelated, domains.

• Health and Functioning Subscale: Items related to physical health, pain, energy, and independence.
• Social and Economic Subscale: Items covering financial security, employment, education, and social environment (neighborhood, home).
• Psychological/Spiritual Subscale: Items assessing mental state, happiness, peace of mind, personal goals, and spiritual beliefs.
• Family Subscale: Items focusing on family health, relationships with spouse/partner, children, and the emotional support received from family and friends.

Instrument

Test Type: Self-report psychological scale/Health Outcome Measure

Format: 66 items (33 pairs), using a 6-point Likert scale. Part I measures satisfaction (1=Very Dissatisfied to 6=Very Satisfied). Part II measures importance (1=Very Unimportant to 6=Very Important).

Language Available: English, Persian, and numerous other translations.

Population Group: General population, clinical populations (e.g., chronic disease patients, including oncology and cardiac patients).

Age Group: Adults.

Population Details: The QLI is designed to be applicable across diverse adult populations, allowing for generalized and specialized applications in health and psychological research.

Test Methodology: The final QLI score is calculated by weighting the satisfaction score for each item by its corresponding importance score, resulting in a single comprehensive index score that reflects the individual’s unique valuation of life domains.

Keywords

Health and functioning, social well-being, psychological assessment, spiritual well-being, weighted scoring, clinical research, psychometric assessment, nursing science.

Authors

Author ORCID Identifier: Not provided in source.

Affiliation Email addresses: [email protected]

Correspondence Address: Carol Estwing Ferrans, PhD, FAAN, University of Illinois at Chicago, College of Nursing (M/C 802), 845 S. Damen Avenue – 7th floor, Chicago, IL 60612 U.S.A. Phone (312) 996-8445, Fax (312) 996-4979.

Permissions & Fee and Test Year

The initial development and publication of the Quality of Life Index occurred in 1985 (Ferrans & Powers, 1985). The instrument is managed by the principal author, Carol Estwing Ferrans. Researchers and institutions seeking to use the QLI should contact the author directly for current information regarding permissions, licensing fees, and access to specific versions (e.g., condition-specific adaptations). Further information regarding the instrument can be found at the official resource page: http://www.uic.edu/orgs/qli/.

Reference’s

1. Ferrans, C. (1996). Development of a conceptual model of quality of life. Scholarly Inquiry for Nursing Practice: An International Journal, 10(3), 293-304.
2. Ferrans, C., & Powers, M. (1985). Quality of Life Index: Development and psychometric properties. Advances in Nursing Science, 8, 15-24.
3. Ferrans, C., & Powers, M. (1992). Psychometric assessment of the Quality of Life Index. Research in Nursing and Health, 15, 29-38.
4. Ferrans, C. E. (1990). Development of a quality of life index for patients with cancer. Oncology Nursing Forum, 17(3), 15-19.
5. Warnecke, R., Ferrans, C., Johnson, T., et. al. (1996). Measuring quality of life in culturally diverse populations. Journal of the National Cancer Institute Monographs, 20, 29-38.
6. Rafiei.Narges, Sharifian Sani. Maryam, Rafiey. Hassan, Behnampour. Nasser, Foroozesh, Kian., (2010). Reliability and Validity of Persian Version of “Quality of Life Index”. J Mazandaran University Med Sci 2014; 24(116): 75-83 (Persian).

Items of the Quality of Life Index (QLI)

IMPORTANT: The following scale items must be preserved in their original language and must not be changed in any way.