Discrepancy in Frailty Identification: Move Beyond Predictive Validity

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Abstract

Background: To evaluate the discordance in frailty classification between the frailty index (FI) and the physical frailty phenotype (PFP) and identify factors discriminating those with discordant frailty classification from each other and from those for whom the assessments agree.

Methods: A prospective observational study of older adults aged 65 and older selected from Medicare eligibility lists in four U.S. communities (n = 5,362). The PFP was measured by the Cardiovascular Health Study PFP. Participants meeting three or more of the five criteria were deemed frail. The FI was calculated as the proportion of deficits in an a priori selected set of 48 measures, and participants were classified as frail if FI is greater than 0.35.

Results: The prevalence of frailty was 7.0% by the PFP and 8.3% by the FI. Of the 730 deemed frail by either instrument, only 12% were in agreement, whereas 39% were classified as frail by the PFP, but not the FI, and 48% were classified as frail by the FI, but not the PFP. Participants aged 65-72 years or with greater disease burden were most likely to be characterized as being FI-frail, but not PFP-frail. The associations of frailty with age and mortality were stronger when frailty was measured by the PFP rather than the FI.

Conclusions: Despite comparable frailty prevalence between the PFP and the FI, there was substantial discordance in individual-level classification, with highest agreement existing only in the most vulnerable subset. These findings suggest that there are clinically important contexts in which the PFP and the FI cannot be used interchangeably.

© The Author(s) 2019. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Physical Frailty Assessment in Older Women: Can Simplification Be Achieved Without Loss of Syndrome Measurement Validity?

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Abstract

Different phenotypes have increasingly been used as tools for clinical characterization of frailty among older adults. Although there have been studies about the comparability and effectiveness of various simplifications and approximations of existing frailty phenotypes for risk prediction, there have been no studies in which investigators evaluated the stability of the clinical characterization achieved. In the present study, we used baseline (1992-1996) data from 786 community-dwelling women who were 70-79 years of age in the Women’s Health and Aging Study I and II to compare physical frailty phenotypes (PFPs). Using the 5 criteria set forth by Fried, we created 15 PFPs that were positive for various combinations of 3 or 4 of those criteria and compared them with the PFP that included all 5 criteria in order to assess construct validity with regard to frailty syndrome characterization and predictive validity for adverse outcomes of aging. All PFPs exhibited high specificity and negative predictive values for identifying frailty syndrome. Three-item PFPs were insensitive but were the best performers for positive predictive value, with the highest positive predictive value of 0.86 seen in the PFP characterized by the combination of weakness, exhaustion, and weight loss. In comparison, the 5-criterion PFP achieved a sensitivity of 0.82 but a positive predictive value of only 0.53. With regard to predictive validity, it was not merely the number of criteria used to characterize the PFPs but rather the specific criteria combinations that predicted the risk of adverse outcomes. Our findings show that there clinically important contexts in which simplified PFPs cannot be used interchangeably.

© The Author 2016. Published by Oxford University Press on behalf of the Johns Hopkins Bloomberg School of Public Health. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

What would make a definition of frailty successful?

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Abstract

At present, frailty is defined variably. Some consensus on a definition is likely to emerge, but the basis for a successful definition needs to be explored. Here, a classic approach to validation is proposed: a successful definition of frailty should be multifactorial but must also manage the many factors in a way that takes their interactions into account. It is likely to be correlated with disability, co-morbidity and self-rated health, and should identify a group that is vulnerable to adverse outcomes. Ideally, it should also be susceptible to animal modelling. In that frailty and age are so bound together, it is also likely that there will be some age at which virtually all people will be frail, by any definition. Apart from being valid, the success of any definition of frailty will depend on it being useful to researchers and clinicians. The need for progress on our understanding of frailty is evident, but for now, there is insufficient evidence to accept a single definition of frailty.

Principles and Issues for Physical Frailty Measurement and Its Clinical Application

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“Frailty” has attracted attention for its promise of identifying vulnerable older adults, hence its potential use to better tailor geriatric health care. There remains substantial controversy, however, regarding its nature and ascertainment. Recent years have seen a proliferation of frailty assessment methods. We argue that the development of frailty assessments should be grounded in “validation”—the process of substantiating that a measurement accurately and precisely measures what it intends, identify unresolved measurement issues, and highlight measurement-related considerations for clinical practice.