International Society for Quality of Life Research
International Society for Quality of Life Research

What Is Health-Related Quality of Life Research?

A number of definitions of health-related quality of life (HRQOL) exist[2-3,5-7]. There is broad agreement that HRQOL is the functional effect of a medical condition and/or its consequent therapy upon a patient[2,6]. HRQOL is thus subjective and multidimensional, encompassing physical and occupational function, psychological state, social interaction and somatic sensation[6].

Goal and Purpose of HRQOL Measurement

As Osoba and King[4] argue, “The ultimate goal of health care is to restore or preserve functioning and well-being related to health, that is health-related quality of life”. Thus, the purpose of HRQOL measurement is to quantify the degree to which the medical condition or its treatment impacts the individual’s life in a valid and reproducible way. HRQOL is an important indicator along with traditional measures (e.g., survival, tumour response) to capture the burden of disease or illness. The gold standard are for patients to self-report their HRQOL; however there may be times when the patient is too ill or too young that may require proxy data on the patient’s HRQOL. These measurements can then be used to measure changes in HRQOL over time (for example in clinical trials, observational studies, healthcare delivery settings, or for population surveillance), to compare the HRQOL of patients with different conditions (e.g., the relative impact of heart disease versus cancer) or who receive different treatments (e.g., within clinical trials or comparative effectiveness research)[3].

Looking to learn more about HRQOL and Patient Reported Outcomes?
Attend an ISOQOL Education Course. 

Patient Reported Outcomes

Patient reported outcomes (PROs) are any report of status that comes directly from the patient, without interpretation of the patient’s response by a clinician or anyone else. Patient reported outcome measures are indexes, scales or questionnaires that aim to measure one or more aspects of patient reported outcomes.

PRO measures represent the effect of the disease as well as the positive and negative consequences of treatment on health and functioning from the patient’s perspective. They measure the relative or absolute change in health related concepts such as

  • Signs
  • Symptoms
  • Functions
  • More complex, multidimensional concepts

Development and Testing of PRO Measures

ISOQOL’s guidance on the minimum standards for developing and tests of PRO measures to be used in Patient Centered Outcomes Research is based on review of published guidance documents and the results of the ISOQOL membership survey. Researchers should take in to consideration the following when developing a new PRO measure or selecting an existing measure for use in an investigation.

Definition of PRO Measure Properties Conceptual and Measurement Model
The conceptual model provides a description and framework for the targeted construct(s) to be included in a PRO measure. The measurement model maps the individual items in the PRO measure to the construct.

The degree to which a PRO measure is free from measurement error.

Internal Consistency Reliability
The degree of the interrelatedness among the items in a multi-item PRO measure.

Test-Retest Reliability
A measure of the reproducibility of the scale, i.e., the ability to provide consistent scores over time in a stable population.

The degree to which a PRO instrument measures the PRO concept it purports to measure.

Content Validity
The extent to which the PRO measure includes the most relevant and important aspects of a concept in the context of a given measurement application.

Construct Validity
The degree to which scores on the PRO measure relate to other measures (e.g., patient-reported or clinical indicators) in a manner that is consistent with theoretically derived a priori hypotheses concerning the concepts that are being measured.

Criterion Validity
The degree to which the scores of a PRO measure are an adequate reflection of a “gold standard”.

The extent to which a PRO measure can detect changes in the construct being measured over time.

Interpretability of Scores
The degree to which one can assign easily understood meaning to a PRO measure’s scores.

The time, effort, and other demands placed on those to whom the instrument is administered (respondent burden) or on those who administer the instrument (investigator or administrative burden).

Applying PRO Measures in Areas of Research

Patient reported outcomes (PROs) focus on the well-being of patients. It is important that these outcomes are measured in research to ensure that the patient’s perspective is captured. Patient reported outcome measures are used to measure PROs and can be assessed as a primary or secondary research outcome and used to evaluate disease or treatment outcomes. The domains chosen for inclusion depend on the context of the research. Ahmed, et al[1] and on behalf of the International Society for Quality of Life Research recommend that the choice to be driven by:

  1. The goals of the study
  2. The patient population of interest
  3. The interventions being compared
  4. Whether evidence will be generated through experimental methods (e.g., clinical trials) or through clinical monitoring and observational or retrospective assessment
  5. The expected timeline for generating evidence

The types of research that PRO measures can be integrated into include: comparative effective research (CER) comparing two interventions, service evaluation, and clinical trials. PRO measures can be used to evaluate either a disease or treatment outcome.

Applying PRO Measures in Clinical Practice

The goal of health care is to make patients feel better and PRO measures can have an important role in assessing whether this has been achieved in routine clinical care. PRO measures can be collected and used for a number of different purposes in routine clinical practice. ISOQOL’s Clinical Practice Special Interest Group has put together a User’s Guide to help clinicians implement PRO measures collection in clinical practice. They recommended that clinicians need to consider the following issues:

The Goals for Collecting PRO Measures in Clinical Practice
For example, screening or detection of problems, monitoring patient’s problems over time or promoting patient centred care.

Selecting the patients, setting and timing for PRO Measure assessment
This can have significant implications for the resources needed.

Determining Which PRO Measure to Use
For example, generic vs disease specific, profile vs preference based measures.

Mode of Administration
For example, selecting between self, interviewer, computer, or web based completion.

Reporting PRO Measures
This includes determining how to fit PRO measures into the clinical workflow, identifying who will receive the reports, deciding when they will receive the reports, and how often and the format of the score reports.

Interpreting PRO Measures
For example, guidelines on score meaning, cut off scores that might indicate a problem, reference scores from populations with the same condition or for changes over time, and the minimal clinically important difference.

How to Respond to Issues Identified by the PRO Measure
For example, the use of guidelines to deal with issues raise, directories of services available to address HRQOL issues and training clinicians to interpret scores

Evaluating the Impact of PRO Measures Feedback on the Practice
Different study designs have costs and benefits in terms of their risk of bias and their feasibility in routine practice.


  1. Ahmed, S, Berzon, R.A., Revicki, D.A., Lenderking, W.R., Moinpour, C.M., Basch, E., Reeve, B.B., Wu, A.W., on behalf of the International Society for Quality of Life Research, (2012). The Use of Patient-reported Outcomes (PRO) Within Comparative Effectiveness Research: Implications for Clinical Practice and Health Care PolicyMedical Care, doi: 10.1097/MLR.0b013e318268aaff.
  2. Cella D (1995). Measuring quality of life in palliative care. Seminars in Oncology 22:73-81.
  3. Guyatt GH, Feeny DH, Patrick DL (1993). Measuring health-related quality of life. Annals of Internal Medicine 118:622-628.
  4. Osoba D, King M. Meaningful differences. In: Fayers P, Hays RD, eds. Assessing quality of life in clinical trials. Oxford Press: New York, 2005. 244-257.257.
  5. Patrick DL, Erickson P. Assessing health-related quality of life for clinical decision making. In: Walker SR, Rosser RM, eds. Quality of life: assessment and application. Lancaster, England: MTP Press, 1988, Chapter 1, p. 22
  6. Schipper H, Clinch, JJ, Olweny CLM (1996) Quality of life studies: definitions and conceptual issues, In Spilker B (ed) Quality of Life and Pharmacoeconomics in Clinical Trials. Lippincott-Raven Publishers:Philadelphia. PP 11-23.
  7. World Health Organization (1958). The First Ten Years of the World Health Organization. Geneva: World Health Organization.

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Throughout the website, ISOQOL provides outside resources that may provide assistance to people interested in health-related quality of life and its assessment. It is recommended that readers conduct their own evaluation of the information outside of ISOQOL activities.


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