Frailty measures are essential to include in clinical practice so one can develop various interventions for resulting disability for older adults. Over the years, several instruments for assessing frailty have been used.
One of the scales most commonly used is the Clinical Frailty Scale (CFS). It evolved from the Canadian Study of Health and Aging. It provides a summary tool for clinicians to assess frailty and fitness. The CFS is a judgement-based frailty tool that evaluates specific elements including comorbidity, function, and cognition to generate a frailty score ranging from 1 (very fit) to 9 (terminally ill).
Applying the CFS to patients requires clinical judgment on the part of the examining clinician and thus may be subjected to inter-observer variation. Although the CFS is touted as a quick and easy test, it does require data collection beyond that which could be collected by a cursory evaluation. It does entail watching the patient (mobilize) and inquiring about their habitual physical activity and ability. It requires the clinicians to assess if the patient can independently perform tasks such as bathing, dressing, housework, going upstairs, going out alone, going shopping, taking care of finances, taking medications, and preparing meals. The main advantage besides its validity is that it is easy to use and may readily be administered in a clinical setting. 
Clinical Frailty Scale Components
- Very Fit: People who are robust, active, energetic, and motivated. These people commonly exercise regularly. They are among the fittest for their age.
- Well: People who have no intense disease symptoms but are less fit than category 1. Often, they exercise or are very active occasionally, e.g., seasonally.
- Managing Well: People whose medical problems are well controlled, but are not regularly active beyond routine walking.
- Vulnerable: While not dependent on others for daily help, often symptoms limit activities. A common complaint is being “slowed-up” and being tired during the day.
- Mildly Frail: These people usually have more evident slowing, and need help in higher-order instrumental activities of daily living (IADLs) such as finance, transportation, heavy housework, medications. Typically, mild frailty progressively impairs shopping and walking outside alone, meal preparation, and housekeeping.
- Moderately Frail: People need help with all outside activities and with keeping house. Inside, they often have problems with stairs and need help with bathing and might need minimal assistance (stand-by) with dressing.
- Severely Frail: Completely dependent on personal care from whatever cause (physical or cognitive). Even so, they seem stable and not at high risk of dying (within six months).
- Very Severely Frail: These patients are completely dependent, approaching the end of life. Typically, they could not recover even from minor illnesses.
- Terminally Ill: Approaching the end of life. This category applies to people with a life expectancy of under 6 months, who are not otherwise evidently frail.
A recent study published in BMC Geriatrics in October last year looked at the utility of CFS by assessing the nature and extent of research evidence related to the CFS. Their review revealed that the CFS has been widely used in multiple settings and that the association of CFS score with clinical outcomes highlights its utility in the care of the ageing population. 
They found that CFS was predictive in 74% of the cases. Mortality was the most common outcome examined with CFS being predictive 87% of the time. CFS was associated with comorbidity 73% of the time, complications 100%, length of stay 75%, falls 71%, cognition 94%, and function 91%. The CFS was associated with other frailty scores 94% of the time.