Table 1. Main frailty tools used in ACS setting and the prognostic value of frailty assessed by these tests.

Brief description		Pros	Cons	Prognostic implication in ACS
Scales based on interview, without objective assessment of physical performance
FRAIL scale	Five items about fatigue, resistance, ability to walk for one block, concomitant illnesses and loss of weight. Frailty is defined by the presence of 3 or more criteria.	Multidomain evaluation Inclusion of comorbidities	Time required. Few evidences in ACS. Lacking inclusion of relevant laboratory data.	Predictor of 6-monthall-cause death.[6]
Frailty Index	Evaluation based on 32 different variables about symptoms, signs, disabilities, diseases, and laboratory measurements obtaining final point with a threshold of 0.25 defining frailty.	Multidomain evaluation	Time required.	Association with long-term mortality and myocardial Infarction.[7]
CFS	Nine frailty levels ranging from 1 (very fit) to nine (terminally ill); the degree of frailty can be assessed by simple questions, according to the description encoded for every level.	Ease Convenience Speed practical	Biased by subjective considerations. Lacking multidomain evaluation. Lacking inclusion of relevant clinical and laboratory data.	Association with increased risk of in-hospital and 1-month death and increased length of stay.[1],[8]–[11]
Scales with objective assessment of physical performance
Fried criteria	Fvie criteria: unintentional weight loss > 4.5 kg in the past year, exhaustion, physical activity, walk time and grip strength (frailty is defined by the presence of three or more criteria).	Strong evidence of frailty identification Multidomain evaluation	Need of training with a geriatrician Time required. Lacking inclusion of relevant clinical and laboratory data.	Strong predictor of mortality and myocardial infarction.[12]–[14]
SHAREFI	Six items: exhaustion, appetite, physical activity, ambulation, resistance and measurement of grip strength.	Multidomain evaluation Speed practical	Self-reported. Lacking inclusion of relevant clinical and laboratory data.	Association with early complications and survival.[15]
EFS	Questions and tasks about nutrition, symptoms, mood and physical performance and it ranges from 0 (not frail) to 17 (very frail).	Multidomain evaluation	Time required. Lacking inclusion of relevant laboratory data.	Association with length of stay, 1-year mortality and undertreatment.[16],[17]
Green score	Scale of four items (physical activity, serum albumin, gait speed, grip strength) ranging from 0 to 12.	Multidomain evaluation including laboratory data	Lacking inclusion of clinical data such ad comorbidities.	Predictive value for all-cause death and death/re-infarction.[14]
Measurements of physical performance
Grip strength	Assessment of the force of the flexor muscles of the fingers, wrist and forearm by a dynamometer.	Ease Convenience Speed practical	Lacking multidomain evaluation. Lacking inclusion of relevant clinical and laboratory data.	Predictive value for cardiac death, all-cause death and hospital admission for heart failure.[18],[19]
Gait Speed	Evaluation of walking speed with a usual pace for some meters, the length of five to ten meters is the most used. Slow gait speed is defined as a value ≤ 0.8 m/s.	Ease Convenience Speed practical	Lacking multidomain evaluation. Lacking inclusion of relevant clinical and laboratory data.	Predictive value for 1-year mortality and hospital Readmission.[20]
SPPB	Assessment of lower limb function according to three tests: standing balance, usual walking speed and standing chair. The score ranges from 0 (worst performance) to 12 (best performance). Physical performance is considered reduced with a SPPB score ≤ 9.	Multidomain evaluation of physical performance	Need of training with geriatrician. Lacking inclusion of relevant clinical and laboratory data.	Ongoing study about its usefulness in ACSpatients.[25]

ACS: acute coronary syndrome; CFS: clinical frailty scale; EFS: Edmonton frail scale; SHARE-FI: Survey of Health, Ageing and Retirement in Europe Frailty Instrument; SPPB: short physical performance battery.