Quality of Life is defined as ''an individual's perception of their position in life in the context of the culture and value systems in which they live and in relation to their goals,expectations, standards and concerns’' by The World Health Organization (THE WHOQOL GROUP, 1994).
It is important to assess quality of life in clinical trials as health professionals and researcher, and the patient often have different perceptions about the same topic - what the professional considers to be "successful" is not always considered as such by the patient.
Our team questioned: What’s the most appropriate instrument for clinical research and practice? This article summarises the review conducted by our research team in order to evaluate the options when measuring Quality of Life in clinical trials.
How to measure Quality of Life in clinical trials?
Five questionnaires to assess Quality of Life were analyzed in the present study:
- World Health Organization Quality of Life Assessment Instrument (WHOQOL)
- Medical Outcomes Study 36-item Short-Form Health Survey (SF-36)
- Medical Outcomes Study 12-item Short-Form Health Survey (SF-12)
- Nottingham Health Profile (NHP)
- Euro-Quality of Life Questionnaire (EuroQoL, EQ-5D).
The surveys were selected based on an electronic search. Relevant studies were collected from the following databases:
EQ-5D, SF-12, SF-36,and WHOQOL were selected to be evaluated according to the criteria suggested by Aaronson et al, 2002, where the authors address the importance of eight domains:
- conceptual and measurement model
- respondent and administrative burden
- alternate forms
- cultural and language adaptations
A sub-set were then compared following Hyland 2003 criteria for an ideal cross-sectional questionnaire (single-use):
- Simple(e.g., binary or tertiary) response format
- Items cover the whole severity range of QoL deficit
- Items with floor and ceiling effects should be included
- Items need not be relevant to all patients
- Items irrelevant to the disease should not be included (unless the scale is to be sensitive to co-morbidity)
Of the five QoL questionnaires identified, SF-36 was the most widely used. However, in cardiovascular disease studies it was the WHOQOL.
EQ-5D and the SF-12were selected as adequate. The main disadvantage of the EQ-5D questionnaire was its ceiling effect, and the main advantage of the SF-12 are more refined answer options. Quality of Life SF-12 covers mood and energy – lacks sleep pattern and sleep quality data. Different variables that may affect the results of the Quality of Life questions. Understanding the patient perception about their condition and how it has already been impacting their lives can help in the management of multiple morbidities.
Limitation about questionnaires and surveys is the fact that the final score can be affected by the way the instrument is applied. The way the questionnaires are applied has a direct influence on the final result of each score:
- factors that cannot be modified: number of questions, the number of questionnaires and sociodemographic factors
- factors that can be modified: health professional/researcher will conduct the visit and will explain about the data collection to the patient
Patients in situations of vulnerability feel discriminated when attending health appointments. Identify patients concerns and perceptions is crucial to the success and support of treatment.