**2. Reliability of frailty models in elderly population studies**

Geriatrics, as a branch of clinical sciences, is a scientific discipline as physics or chemistry is to natural sciences. To that end, measurements are the core aspect for its sustainability. It is under this framework that most frailty scales are available the world over to date, and in future shall be assessed. Technically, assessing the quality aspects of the scale takes mainly two domains, namely, *reliability* and *validity*. Taken simply, reliability assessment refers to the process of determining the extent to which a measurement of a phenomenon provides stable and consistent results [17]. This definition, though adopted from Carmine and Zeller's publication of 1979 [17], who worked in the field of psychometrics, is as applicable, in its entirety to frailty scale assessment, as it was intended in assessing psychometric scales. Thus, whereas the intention here is to adopt quantifiable and logically consistent manner for reliability assessment of frailty scales, it is by no means the intention of the author to *sales pitch* the methods discussed nor should it be conclusive that the method described in this chapter is the only mechanism of achieving reliability assessment. To ensure clarity in this endeavor, the end of the chapter will also contain some vivid shortcomings and a potential solution to the reliability assessment method described in this chapter.

#### **2.1 Internal consistency assessment of frailty scales used in elderly population**

There are various ways of assessing reliability index of any given phenomenon/ scale in nature. Some are well known in literature, and there are probably many others in production pipelines for usage in future. However, the most popular methods include test-retest reliability, split-half reliability, and internal consistency reliability tests. Out of these, this chapter will deal with internal consistency reliability. The decision to do so is derived from its conceptual meaning as opposed to the rest. Simply stated, internal consistency refers to the extent to which a measurement of a scale provides stable and consistent results across a specified condition [17]. One rule is important to be mentioned here, in that all accounts of assessing reliability of any given scale, the reliability score to be obtained is not reflective of a constancy but rather a mere statistic for a given test result. This translates to the fact that a given scale may end up with different scores, under different elderly population conditions, dependent on a number of factors, some known (e.g., test settings and gender) and others unknown even to the test itself. Thus, caution to the interpretation of the test scores is highly warranted.

#### *2.1.1 Clinical Frailty Scale*

Clinical Frailty Scale (CFS) is a clinical judgment-based tool (originally designed as an epidemiological tool) to screen for frailty and other adverse health events in opposition to fitness in older aged population. It is a direct replica of a frailty index that was part of the original design aspect of the first part of Canadian Study on Health and Aging (CSAH), with the aim of characterizing cognitive impairment and other important health issues, designed as a prospective 5-year follow-up of 10,263 people aged at least 65 years back in 1991 [18, 19]. At the time of going to

press, the Clinical Frailty Scale is composed of a 9-point scale, that was made public in 2007, an improvement from the original scale of a 5-point scale originally published in 2005 [20]. It was originally developed in the second half of the Canadian Study of Health and Aging (CSHA) as a quick means to assess frailty and other senile physical and mental challenges past clinical assessment [20]. The conceptual framework of the Clinical Frailty Scale relies on the "fitness and frailty" model, and the scale was designed by adopting the mechanism from Streiner and Norman [21]. It is for all practical purposes, not a questionnaire but a quantified summary write-up of an elderly overall health status in relation to mortality risks. Internal consistency scores for Clinical Frailty Scale among elderly population across different geographical areas are provided in **Table 1**.

#### *2.1.2 Edmonton Frail Scale (EFS)*

Edmonton Frail Scale, an effort first conceptualized by Darryl Rolfson while at the University of Alberta, Canada back in 1999, was presented for the first time to peer review at the Canadian Geriatric Society in Edmonton, Canada, in 2000 [25]. Ever since its first time in press, the scale has been applied in research, educational and clinical settings for quantitative frailty assessment among senior citizens [15, 26**–**33]. Edmonton Frail Scale consists of nine domains and 11 items. The initial scale devised by Rolfson at Edmonton had 10 domains [25]. Each component may have a score of 0, 1, or 2 signifying normal health, mild/moderate impairment, or severe impairment, respectively. Domains include general health status; cognitive status; medication use; presence of social support; incontinence; nutrition and mood; functional dependency; and functional performance test [25]. The total scores are also classified into no frailty (0–3 points); pre-frailty (4–5 points); frailty (6–8 points), and severe frailty (9–17) [26]. The internal consistency scores of Edmonton Frail Scale for senior citizens across different geographical settings are as reported here in **Table 2**.

#### *2.1.3 Groningen Frailty Indicator*

Groningen Frailty Indicator (GFI) is a 15-item indicator for assessment of frailty developed by Professor Steverink and his colleagues at the University of Groningen, The Netherlands, first published in 2001 [34]. The internal consistency findings of GFI are as summarized in **Table 3**.

#### *2.1.4 Tilburg Frailty Indicator*

Tilburg Frailty Indicator (TFI) is a questionnaire for screening frail community dwelling older people that includes self-reported information, originally tested and validated from an elderly community of Roosendaal in The Netherlands, based on


#### **Table 1.**

*Internal consistency scores for Clinical Frailty Scale across elderly population from different geographical areas.*

*Reliability and Validity of Clinicopathological Features Associated with Frailty Syndrome… DOI: http://dx.doi.org/10.5772/intechopen.93499*


#### **Table 2.**

*Internal consistency scores for Edmonton Frail Scale across senior citizens from different geographical areas.*


#### **Table 3.**

*Construct validity scores for Groningen Frailty Indicator across senior citizens in different geographical areas.*


#### **Table 4.**

*Construct validity scores of Tilburg Frailty Indicator across senior citizens in different geographical areas.*

a working framework in development, developed by a team of Dutch scientist first published in 2009 [38]. Tilburg Frailty Indicator is unique among frailty indicators, in that it includes multiple domains of human functions but selectively excludes disability [38]. TFI consists of two parts, namely, multimorbidity and frailty domains. The first part (designated as part A) contains 10 questions on determinants of frailty in relation to disease states, while the second part is solely on frailty aspects [38]. The internal consistency score ratings of TFI across studies from different geographical areas are given in **Table 4**.
