Background: Frailty can lead towards serious adverse consequences, such as disability. With regard to prevention valid screening instruments are needed to identify frail older people. The aim was to evaluate and compare the psychometric properties of three screening instruments: the Groningen Frailty Indicator (GFI), the Tilburg Frailty Indicator (TFI) and the Sherbrooke Postal Questionnaire (SPQ). For validation purposes the Groningen Activity Restriction Scale (GARS) was added.
Methods: A questionnaire was sent to 687 older people (> or = 70 years). (1) Agreement between instruments, (2) internal consistency, (3) cumulative scalability according to Mokken scale analysis and (4) construct validity were evaluated.
Results: The response rate was 77%. Prevalence estimates of frailty ranged from 40% to 59%. The highest agreement was found between the GFI and TFI (Cohen's kappa = 0.74). Cronbach's alpha for the GFI, TFI and SPQ was 0.73, 0.79 and 0.26, respectively. The scalability of the three instruments was inadequate (Loevinger's H: 0.28, 0.30 and 0.09 for GFI, TFI and SPQ, respectively). Frailty scores correlated significantly with each other and with the GARS scores.
Conclusion: Especially the GFI and TFI seem to be useful to identify frail older people. Further research regarding their predictive validity is still needed.