Reproducibility and responsiveness of the Frailty Index and Frailty Phenotype in older hospitalized patients

Abstract

Background There is growing interest for interventions aiming at preventing frailty progression or even to reverse frailty in older people, yet it is still unclear which frailty instrument is most appropriate for measuring change scores over time to determine the effectiveness of interventions. The aim of this prospective cohort study was to determine reproducibility and responsiveness properties of the Frailty Index (FI) and Frailty Phenotype (FP) in acutely hospitalized medical patients aged 70 years and older. Methods Reproducibility was assessed by Intra-Class Correlation Coefficients (ICC), standard error of measurement (SEM) and smallest detectable change (SDC); Responsiveness was assessed by the standardized response mean (SRM), and area under the receiver operating characteristic curve (AUC). Results At baseline, 243 patients were included with a median age of 76 years (range 70–98). The analytic samples included 192 and 187 patients in the three and twelve months follow-up analyses, respectively. ICC of the FI were 0.85 (95 % confidence interval [CI]: 0.76; 0.91) and 0.84 (95% CI: 0.77; 0.90), and 0.65 (95% CI: 0.49; 0.77) and 0.77 (95% CI: 0.65; 0.84) for the FP. SEM ranged from 5 to 13 %; SDC from 13 to 37 %. SRMs were good in patients with unchanged frailty status (< 0.50), and doubtful to good for deteriorated and improved patients (0.43–1.00). AUC’s over three months were 0.77 (95% CI: 0.69; 0.86) and 0.71 (95% CI: 0.62; 0.79) for the FI, and 0.68 (95% CI: 0.58; 0.77) and 0.65 (95% CI: 0.55; 0.74) for the FP. Over twelve months, AUCs were 0.78 (95% CI: 0.69; 0.87) and 0.82 (95% CI: 0.73; 0.90) for the FI, and 0.78 (95% CI: 0.69; 0.87) and 0.75 (95% CI: 0.67; 0.84) for the FP. Conclusions The Frailty Index showed better reproducibility and responsiveness properties compared to the Frailty Phenotype among acutely hospitalized older patients.

Reliability of the Frailty Index Among Community-Dwelling Older Adults

“…Test–retest reliability of the FI over multiple 14-day periods was ICC = 0.88, which is slightly above the results reported for stable hospital patients over 3 months (ICC = 0.84/0.85) ( 29 ). Our estimate also compares favorably with the range of test–retest ICCs reported for other frailty instruments, for example, 0.65/0.77 for phenotypic frailty over 3 months ( 29 ), 0.71 for the FRAIL scale over 7–15 days ( 46 ), and 0.88 for the Tilburg Frailty Indicator over 10–25 days ( 47 ). In sum, test–retest reliability, as well as internal consistency of the FI were good, and hence the FI can be considered a high-quality instrument for risk stratification among older adults.…”

“…(3) Measurement error, finally, is relevant for frailty monitoring, that is, to differentiate “real” frailty changes from error or “noise,” and can be assessed with the standard error of measurement (SEM) ( 27 ). To date, only 2 studies ( 28 , 29 ) provide estimates of the reliability of the standard clinical FI ( 30 ). Based on a large cross-national sample of community-dwelling older adults and confirmatory factor analysis (CFA), Mayerl and colleagues ( 28 ) reported internal consistency (omega) of 0.89–0.93.…”

“…Based on a large cross-national sample of community-dwelling older adults and confirmatory factor analysis (CFA), Mayerl and colleagues ( 28 ) reported internal consistency (omega) of 0.89–0.93. Based on 80 stable hospital patients over 3 months, Feenstra et al ( 29 ) reported a test–retest reliability (ICC) of 0.84 and a measurement error (SEM) of 0.06. Although these first studies suggest the FI to be reliable, more evidence is needed against the background of the current and intended future use of the FI in both research and clinical practice.…”

Predictive Abilities of the Frailty Phenotype and the Swiss Frailty Network and Repository Frailty Index for Non-Home Discharge and Functional Decline in Hospitalized Geriatric Patients

“…The much lower prevalence may be explained by the fact that included patients were almost all functionally independent compared to our study population consisting of comorbid patient with a limited functional score. Moreover, the frailty phenotype in the study of Feenstra et al ( 26 ) was solely based on self-reported items possibly underestimating frailty whereas the frailty phenotype in our study included clinical measures such as gait speed and grip strength.…”

“…Some studies reported very similar prevalence, such as Bieniek et al who described a prevalence of 54.2% based on the Fried frailty phenotype in geriatric inpatients ( 25 ) or Chong et al described a 50.0% prevalence based on the FRAIL scale ( 11 ). However, there are also studies that reported a lower prevalence, such as 19% based on a frailty phenotype defined as self-reported items of weight loss, exhaustion, slowness, weakness, and low physical activity in hospitalized medical patients aged 70 years and older ( 26 , 27 ). The much lower prevalence may be explained by the fact that included patients were almost all functionally independent compared to our study population consisting of comorbid patient with a limited functional score.…”