Psychometric properties of the Brazilian version of the Tilburg frailty indicator (TFI)

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Abstract

This study aims to assess the psychometric properties of the Brazilian version of the TFI, an instrument that identifies frailty in elderly individuals. We interviewed 219 individuals aged 60 or older, living in the community. Individuals were predominantly female (52.5%) and mean age was 70.5 (±7.9) years. In order to assess test–retest reliability, 101 individuals were re-interviewed by the same observer within seven to ten days after the first interview. The internal consistency of the instrument was assessed using Cronbach's alpha. To assess construct validity, we used established alternative measures for the items that constitute the TFI, such as: body mass index (BMI), timed up and go (TUG) test, whisper test, Snellen test, upper extremity strength clinical test and mini-mental state examination (MMSE). The test–retest reliability showed high percent agreement for all the items of the instrument, with values ranging from 63% to 100%. Test–retest reliabilities were good (total TFI score r = 0.88; physical domain r = 0.88; psychological domain r = 0.88; and social domain r = 0.67). Internal consistency reliability of the Brazilian version was satisfactory (Cronbach's alpha = 0.78). The correlations between TFI items and their corresponding measures were consistent except for one item (related to “ability to deal with problems”), demonstrating both convergent and divergent construct validity of the TFI and its items. After the completion of all stages of transcultural adaptation, the Brazilian version of the TFI proved to be well suited for assessing frailty in the elderly population of Brazil.

Introduction

In the last few decades, studies about frailty are becoming increasingly frequent in the scientific literature about aging (De Vries et al., 2011, Sternberg et al., 2011). Frailty results from the diminished physiological reserve and ability to maintain homeostasis in elderly individuals. Frailty makes elderly individuals more vulnerable to environmental stressful situations and is associated with high risk of adverse health outcomes such as functional dependence, falls, recurrent hospitalization and death (Ávila-Funes et al., 2008, Berges et al., 2009, Ensrud et al., 2008, Fried et al., 2001, Van Kan et al., 2008).

Ever since the term frailty appeared in the literature, two conceptual approaches have been adopted. One of the approaches to frailty focuses on factors regarding an elderly individual's physical functioning (Folson et al., 2007, Fried et al., 2001), whereas the other also includes some psychological and social factors (Frieswijk et al., 2004, Gobbens et al., 2010a, Rockwood et al., 1999). The latter multidimensional concept of frailty has currently been the most prevailing (Rothman et al., 2008, Van Kan et al., 2008).

A systematic review of Brazilian literature on instruments identifying frailty in elderly individuals revealed that no multidimensional instrument yet exists in Portuguese. Therefore, we aimed to identify an instrument in the international literature, which addressed the multidimensional concept of frailty and that had been validated in its original culture, showing satisfactory psychometric properties. The TFI was the single instrument which met such requirements (Gobbens et al., 2012, Gobbens et al., 2010b). A recent systematic review concluded that the TFI is potentially relevant for screening for frailty in a primary care setting (Pialoux, Goyard, & Lesourd, 2012). Hence we selected the TFI and submitted it to the process of transcultural adaptation for use in the Brazilian elderly population. The TFI, developed in the Netherlands, consists of two different parts. One part addresses potential determinants of frailty and the other specifically addresses components of frailty. We examined the second part on components of frailty, which consists of fifteen questions, covering the physical, psychological and social domains of frailty. The first stages of the transcultural adaptation of the TFI for use in the elderly population of Brazil have already been completed. We observed good comprehension and reasonable acceptance of the items of the Brazilian version in the pre-test (Santiago, Luz, Mattos, & Gobbens, 2012). This suggests that the instrument may be a useful tool to assess frailty in Brazil.

The aim of this study was to assess the psychometric properties (reliability and construct validity) of the Brazilian version of the TFI.

Section snippets

Study population

From March to June 2012, we recruited a convenience sample of 219 individuals, aged 60 or older. These individuals lived in the community and were assessed at a senior healthcare facility, located in the municipality of Juiz de Fora, in the southeast of Brazil. All recruited individuals agreed to participate and were interviewed by a trained nurse. The first 118 were also submitted to interview and physical measurements of frailty in order to evaluate the validity of the Brazilian version of

Participants characteristics

Mean age of all participants was 70.5 (7.9) with a median of 69.0 years, 52.5% was female, and the majority had a low level of education (67.7% with 0–4 years of education). See Table 1 for participant characteristics as assessed with part B of the TFI, by samples 1 and 2. Prevalence of frailty based on the Brazilian version of the TFI was 35.6% and 31.7%, for sample 1 and 2, respectively, T-tests and chi-square tests showed no statistically significant differences between the two samples.

Discussion

This study was conducted to continue the process of transcultural adaptation of the original TFI to the Brazilian population, according to the universalist approach proposed by Herdman, Fox-Rushby, and Badia (1998). We report on the psychometric properties (test–retest reliability, internal consistency and convergent and divergent validity) of the Brazilian version.

The reliability of the Portuguese TFI is good, evidenced by (i) strong test–retest reliability, (ii) fair to high simple and

Conflict of interest statement

Authors declare no conflict of interest.

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