Psychometric characteristics of the Functional Assessment of Cancer Therapy-General when applied to Brazilian cancer patients: a cross-cultural adaptation and validation.

Juliana Alvares Duarte Bonini Campos,Sergio Vicente Serrano,Maria Cláudia Bernardes Spexoto,João Maroco

doi:10.1186/s12955-015-0400-8

Abstract

BackgroundThe psychometric properties of an instrument should be evaluated routinely when using different samples. This study evaluated the psychometric properties of the Functional Assessment of Cancer Therapy-General (FACT-G) when applied to a sample of Brazilian cancer patients.MethodsThe face, content, and construct (factorial, convergent, and discriminant) validities of the FACT-G were estimated. Confirmatory factor analysis (CFA) was conducted the ratio chi-square by degrees of freedom (χ2/df), the comparative fit index (CFI), the Tucker-Lewis index (TLI), and the root mean square error of approximation (RMSEA) as indices. The invariance of the best model was assessed with multi-group analysis using the difference of chi-squares method (Δχ2). Convergent validity was assessed using Average Variance Extracted (AVE) and discriminant validity was determined via correlational analysis. Internal consistency was assessed using the Cronbach’s alpha (α) coefficient, and the Composite Reliability (CR) was estimated.ResultsA total of 975 cancer patients participated in the study, with a mean age of 53.3 (SD = 13.0) years. Of these participants, 61.5 % were women. In CFA, five correlations between errors were included to fit the FACT-G to the sample (χ2/df = 8.611, CFI = .913, TLI = .902, RMSEA = .088). The model did not indicate invariant independent samples (Δχ2: μ: p < .001, i: p < .958, Cov: p < .001, Res: p < .001). While there was adequate convergent validity for the physical well-being (AVE = .54) and social and family Well-being factors (AVE = .55), there was low convergent validity for the other factors. Reliability was adequate (CR = .76–.89 and α = .71–.82). Functional well-being, emotional well-being, and physical well-being were the factors that demonstrated a strong contribution to patients’ health-related quality of life (β = −.99, .88, and .64, respectively).ConclusionThe FACT-G was found to be a valid and reliable assessment of health-related quality of life in a Brazilian sample of patients with cancer.

Highlights

The psychometric properties of an instrument should be evaluated routinely when using different samples
The disorganization of the Health-related quality of life (HRQOL) of patients with cancer can have a significant negative impact on treatment response, symptoms associated with the disease/treatment, disease prognosis, and the development of unpleasant concomitant clinical conditions
Given the increase in generic measures for assessing HRQOL, there is a need for instruments that are specific to individuals’ clinical conditions and that consider associated disabilities, limitations, and symptoms specific to each condition

Summary

Introduction

The psychometric properties of an instrument should be evaluated routinely when using different samples. This study evaluated the psychometric properties of the Functional Assessment of Cancer Therapy-General (FACT-G) when applied to a sample of Brazilian cancer patients. Since HRQOL is a latent variable, (i.e., not directly measurable), many instruments have been developed to evaluate it in the general population (e.g., World Health Organization Quality Of Life Assessment [WHOQOL-100] [12,13,14,15,16], Medical Outcomes Study SF - 36-Short Form Health Survey [17, 18], and the Sickness Impact Profile [19]). Among the instruments proposed in the literature to assess HRQOL in cancer patients, the two most frequently used instruments used worldwide are the Cella et al.’s Functional Assessment of Cancer Therapy-General (FACT-G) [10] and the European Organization for Research and Treatment of CancerQuality of Life Questionnaire Core 30 (EORTC QLQC30) [20]

Methods

Results

Discussion

Conclusion