Introduction

The definition of quality of life (QOL) according to the World Health Organization (WHO) is: "the individuals' perception of their position in life within the cultural context and value system in which they live and with respect to their goals, expectations, norms, and concerns" ¹. This complex multidimensionality of quality of life implies certain difficulties in its measurement and evaluation, which in turn has facilitated advances in different health interventions ².

In women with breast cancer, their quality of life intimately affects their self-esteem, sexuality and femininity, due to the organ directly involved; they face during the stages of the disease and treatment emotional, physical, mental, and social imbalances that become potential experiences where they themselves are strengthened and motivated to seek other ways to cope with their pathological condition ³. This generates in health professionals the need to measure the quality of life of women who are in different stages of the disease, in order to understand the vital needs and have more elements to incorporate a nursing care plan.

Different questionnaires, both generic and specific, have been used to measure quality of life ⁴. The WHO created the WHO Quality of Life questionnaire (WHOQOL-BREF) as a generic measure of quality of life, seeking to adopt more comprehensive and humanistic measurements. This questionnaire was developed taking into account translation and cultural adaptation and provides consistent information in the different versions ⁵. The WHOQOL-BREF measures quality of life regardless of cultural differences around the world; countries such as Argentina, Brazil, and Panama designed it simultaneously, and it is currently available in more than 30 languages in 40 countries ⁶. The questionnaire consists of 26 Likert-type questions, including one question on global quality of life and another on general health satisfaction, the remaining questions comprise the four domains: physical health (7 items), psychological health (6 items), social relationships (3 items) and environment (8 items) ⁷.

To use a questionnaire reliably, it is necessary to test what it measures, consistently and constantly in the same circumstances ⁽⁸. Reliability can be defined, according to classical theory, as the degree to which a multi-item instrument coherently measures a population sample ⁹. In addition, Cronbach's alpha formula is the one most commonly used to check a consistent measurement; this popular use can be attributed to its importance in psychometric practice, giving great importance to the reliability of measurements ¹⁰. The internal consistency of a questionnaire considers that the minimum satisfactory value for this coefficient is 0.7; this value indicates that the questionnaire presents an acceptable reliability ¹¹.

The quality of life in women with breast cancer has traditionally been measured through generic instruments; however, the usefulness of these instruments in specific conditions has been questioned due to the lack of knowledge of the symptoms of the disease ¹². Therefore, the objective of this integrative review was to determine the reliability of the WHOQOL-BREF questionnaire in studies conducted in breast cancer. The aim of this objective is to motivate the nursing staff to visualize the importance of quality of life as a focal point in the care of women with breast cancer, as well as to provide sufficient elements for the selection of a valid, consistent and applicable questionnaire to the Spanish-speaking population, which will therefore facilitate a reliable evaluation of the quality of life variable in the various research studies, whether experimental (intervention) or non-experimental (descriptive - correlational).

Methodology

The design corresponds to an integrative review, which allows the incorporation of evidence into clinical practice ¹³. This review is recognized by Evidence-Based Nursing (EBN) because it provides results that benefit nursing care, represents another resource for the construction of knowledge, development and precision of clinical practice and its interventions ¹⁴. The following guiding PICO question was posed: What is the reliability of the WHOQOL-BREF questionnaire used in studies conducted in women with breast cancer? Therefore, a literature search was conducted during the months of October and November 2019, using the following descriptors and Boolean, always adhering to the same order: Breast neoplasms AND Quality of life AND WHOQOL BREF questionnaire, available in databases such as: the United States National Library of Medicine (PubMed), Scientific Electronic Library Online (SciELO), Biblioteca Virtual en Salud (BVS), Web of Science (WOS), Trip medical Database (Trip), CINAHL Complete and Elsevier ScienceDirect. Inclusion criteria were: articles demonstrating the reliability of the WHOQOL-BREF questionnaire applied to women with breast cancer, freely available on the web, full text, in English, Portuguese or Spanish languages, published between 2009 and 2019. Exclusion criteria were: studies of women with breast cancer with added pathology. We found 190 original publications after the application of the filters specific to each database (Table 1).

The SciELO database was searched separately for the three languages; in Tripdatabase, CINAHL Complete and Elsevier Science-Direct no filters were used due to the small number of results. After applying the inclusion and exclusion criteria, elimination of duplicates and complete reading, 8 articles were obtained for review (Figure 1).

Source: Own development

Figure 1: Flow chart for article selection.  

Results

For the eight articles included in the study, data summary cards were used to synthesize relevant data and facilitate analysis of the results. The data were duly referenced, identifying the authors. Based on the source of the article, 37.5% of them were indexed in PubMed ^15-17 and VHL ^18-20, and 25% in SciELO ^21,22. 75% of the studies were published between 2009 and 2014 ^18,21,22, and between 2016 and 2018 ^15,16,20, 25% were published in 2015 ^17,19. Regarding the locations where the research was conducted, 37.5% were conducted in Brazil ^18,20,22, and 12.5% in India ¹⁵, Indonesia ¹⁶, Japan ¹⁷, Mexico ¹⁹ and Chile ²¹. The type of study was quantitative; 62.5% of the studies had a cross-sectional correlational design ^{15,17,18,21,22} and 12.5% were cross-sectional descriptive ²⁰, comparative ¹⁶ and pre-experimental ¹⁹.

As for the sample of women with breast cancer, they were found in the different stages of the disease: women with symptoms but without definitive diagnosis ¹⁶, women survivors ¹⁷, women in active treatment or chemotherapy ^18-21, women who underwent surgery ^18,22 and women hospitalized for infiltrating cancer ¹⁵. The total population studied was 1031 women with breast cancer, to whom the WHOQOL-BREF instrument was applied; 87.1% of these women were in treatment or were survivors and 12.8% presented breast symptoms, but without a definitive diagnosis. In these studied populations, the questionnaire showed an overall Cronbach's α coefficient within accepted limits (37.5%), the included studies showed a variation between 0.72 and 0.84, with a mean of 0.79 ^19,20,22 and 62.5% did not mention overall reliability ^15-18,21. Regarding the internal consistency of the questionnaire by domain, 75% of the studies reported internal consistency ^15-18,20-21, variable reliability was found in all domains, with the majority grouped in α values between 0.70 and 0.85, and mean reliability from highest to lowest, as follows: physical health 0.77, psychological health 0.77, social relationships 0.76 and environment 0.72 (Table 2).

Discussion

The objective of this review was to know the reliability of the WHOQOL-BREF questionnaire used specifically in women with breast cancer. The findings in this investigation revealed several important aspects: The WHOQOL-BREF questionnaire has been used considerably in several countries of the world ^23,24, as confirmed in this review that incorporates studies in India, Indonesia, Japan, Mexico, Chile, and Brazil; a growing interest is shown since it identified its use in almost a third of the literature ^18,20,22; likewise, greater use was observed in studies of the correlational type. Since the concept of quality of life has probably taken on great importance in people's lives these days, it encourages the ability to act in different situations and offers a positive feeling about life. In this sense, the emotional state of a person with breast cancer results from the sum of different factors such as the previous quality of life and their different social roles, together with the emotions and feelings present during diagnosis and treatment, which generate a negative impact when facing different types of losses such as: loss of health, loss of employment, loss of hair, loss of breast, among others; in addition, they face different fears and anxieties such as the feeling of imminent death. This requires professional and family support to recover and maintain their quality of life ²⁵.

In recent years, the application of the WHOQOL-BREF questionnaire has progressively increased in the population of women with breast cancer, obtaining heterogeneity in the time of resolution of the disease, ranging from diagnosis and survival to comparison with women without breast cancer ¹⁶. In this regard, the National Institute of Public Health of Mexico tries to highlight the importance of seeking strategies for training health personnel in the diagnosis and approach to breast cancer; undoubtedly, great efforts are required to achieve an organized social response and address breast cancer as a public health problem ²⁶. However, despite therapeutic advances, cancer survival does not guarantee that women with breast cancer have a good quality of life; the current approach is based on continuous surveillance and control treatment, no specific actions and health regulations are identified for the comprehensive management of sequelae that women may present in the survival stage ²⁷.

Regarding the internal consistency of the questionnaire, the studies showed variable reliability in all domains for each selected article, most of them grouped in Cronbach's alpha values between 0.70 and 0.85. The process of validation of the various measurement instruments is an ongoing process; cumulative evidence of validity is needed if any inference and interpretation of instrument scores is to be supported (²⁸). In this regard, researchers ²⁹ indicate that the interpretation and use of Cronbach's alpha can lead to errors, omissions and inaccuracies, as with other psychometric properties in the literature in the English language; the reliability or internal consistency does not lie in the instrument itself but in the scores obtained through it. Cronbach's α coefficients have certain minimum values to consider them from unacceptable to excellent: α ≥ .90 is excellent; α ≥ .80 is good; α ≥ .70 is acceptable; α ≥ .60 is questionable; α ≥ .50 is poor; and α < .50 is unacceptable ²⁹.

The reliability identified in the review was considered appropriate in the different studies, demonstrating that the domains and their respective questions were related and provided an appropriate description of the quality of life of the population studied ³⁰. This was corroborated by comparing the results and visualizing the correspondence between the mean of the global average of reliability with the means of the analysis by domains. The results of this study coincide with the results reported by Kalfoss and collaborators ²⁸, who found that the WHOQOL-BREF questionnaire is one of the most generic and well-known questionnaires for assessing quality of life, both in healthy and sick populations, identifying an adequate use in the general population of Norway. Likewise, the research supported the quality of life (QoL) construct by providing evidence of acceptable convergent and discriminant validity, and internal consistency of the physical, psychological, and environmental domains, as well as invariant factor loadings across gender, education, and age.

The main limitation of the study is considered to be the lack of uniformity in the reporting of reliability with Cronbach's alpha coefficient within the studies included in this review, which prevented a more in-depth general analysis. However, this article seeks to motivate nursing staff to see the importance of quality of life as a focal point in the care of women with breast cancer, as well as to provide sufficient elements for the choice of a reliable questionnaire applicable to the Spanish-speaking population, which consequently facilitates a concise evaluation of the QoL variable in the various research studies, whether experimental (intervention) or non-experimental (descriptive - correlational).

Conclusions

The most important findings showed that the reliability through Cronbach's alpha for the domains comprising the WHOQOL-BREF questionnaire does not differ according to the stage of the disease, which indicates the relevance of its use in women with breast cancer because it is generic. Breast cancer in women represents an alteration in their health, image and relationship with their environment, producing great changes in the different domains of their being: functional, family, emotional and social, which reaffirms the need to measure quality of life with reliable questionnaires such as the WHOQOL- BREF. One of the strengths of the WHOQOL- BREF questionnaire is that it includes the main domains that are affected by breast cancer, which influence the decrease in quality of life. It should be noted, with respect to the stated objective, that the literature is still scarce, so it is necessary to further develop this line of research.

Conflict of interest

The authors declare that they have no conflicts of interest.

Funding

This literature review was not funded.