Introduction The term frailty characterises elders at higher risk for the occurrence of adverse health outcomes in situations of environmental stress. We still do not have an assessment instrument that could be considered as the gold standard for this condition. This study aims to estimate the prevalence of frailty in older individuals living at long-stay institutions, through different instruments, and to evaluate their performance in this setting.

Methods This is a study with elderly residents of long-stay institutions in four Brazilian cities. The prevalence of frailty was estimated with four instruments: Fried phenotype (FP), Frailty Index based on Geriatric Status Scale (GSS-FI), Frail scale (FS) and Edmonton Frail Scale (EFS). The main characteristics of frail individuals according to each instrument were described. Correlations between the categories obtained with each instrument were analysed with Phi's correlation coefficient.

Results These are preliminary results for 340 elders. The estimated prevalence of frailty was 54.3% for FP, 11.3% for GSS-FI, 12.1% for FS and 36.1% for EFS. The mean age of frail individuals varied from 72 to 75 years, depending on the assessment instrument. Frailty predominated in males (60.0–80.0%), 4 or less years of schooling (76.0–91.0%), single (44.0–59.0%) and time in the institution of up to 10 years (64.0–87.0%). The correlation coefficients varied from 0.1 to 0.4 (p<0.05).

Conclusions Although most of the correlations between the instruments were moderate, frailty prevalence varied largely according to the instrument used to assess the condition. These differences are justified because of the different domains assessed by each instrument.