What is the validity and Minimal Clinically Important Difference (MCID) of the Functional Independence Measure (FIM) and Functional Assessment Measure (FAM)?

From the Guidelines

The Functional Independence Measure and Functional Assessment Measure (FIM-FAM) is a valid and reliable assessment tool for measuring disability in patients with neurological conditions, with established Minimal Clinically Important Difference (MCID) values that vary by population. The FIM component has strong validity (construct, concurrent, and predictive) with reliability coefficients typically exceeding 0.85, as noted in the guidelines for adult stroke rehabilitation and recovery 1. While the provided evidence does not directly address the MCID of FIM-FAM, it highlights the importance of comprehensive assessments of body structures and function, activity limitations, and participation restrictions according to the ICF.

The FIM is the most commonly used functional measure in the United States because it is tied to the prospective payment system of the Centers for Medicare & Medicaid Services 1. Although the evidence does not provide specific MCID values for FIM-FAM, it suggests that the FIM is a strong predictor of discharge functional status, discharge destination after inpatient rehabilitation, and length of rehabilitation stay 1.

Some studies have established MCID values for other assessment tools, such as the FM-UE, which has an established MCID for chronic stroke that was derived based on therapists’ evaluation of patients’ global rating of change (GROC) after an intervention 1. However, these values may not be directly applicable to FIM-FAM.

When implementing the FIM-FAM, proper training of raters is essential to maintain reliability, and assessments should be conducted at consistent intervals (typically admission, discharge, and follow-up) to accurately track functional changes during rehabilitation. Clinicians should note that floor and ceiling effects may occur in certain populations, particularly for the cognitive items in minimally impaired patients or motor items in severely impaired patients.

Key considerations for using FIM-FAM include:

• Proper training of raters to maintain reliability
• Consistent assessment intervals to track functional changes
• Awareness of potential floor and ceiling effects in certain populations
• Use of FIM-FAM as part of a comprehensive assessment of body structures and function, activity limitations, and participation restrictions according to the ICF.

From the Research

Validity of FIM-FAM

• The validity of the Functional Independence Measure (FIM) has been explored in several studies, including one published in 2011, which discussed the rationale for using the FIM as an outcomes measure and researched its validity, reliability, responsiveness, and utility 2.
• Another study published in 2009 compared the FIM with the interRAI/MDS for use in the functional assessment of older adults, finding evidence supporting the reliability of both instruments, but noting that additional psychometric research is needed, especially with regard to their use in different settings and with different client groups 3.
• A 2024 study investigated the responsiveness and minimal clinically important difference (MCID) of the FIM in older adults with hip fracture, finding that the FIM showed high responsiveness and that improvements of 22 and 21 points at the total and motor FIM were identified as indicators of minimal clinical change 4.

MCID of FIM-FAM

• The MCID of the FIM has been specifically studied in the context of older adults with hip fracture, with a 2024 study finding that improvements of 22 and 21 points at the total and motor FIM were identified as indicators of minimal clinical change 4.
• The Functional Assessment Measure (FAM) has been proposed as a method to extend the range of the FIM, particularly when assessing functional status in rehabilitation patients with brain injury, including stroke, but a 1999 study found that using the entire FAM as an adjunct to the FIM reduces test efficiency while providing only minimal additional protection against ceiling effects 5.
• A 2018 study compared the sensitivity to change of the FIM with the Assessment of Motor and Process Skills within different rehabilitation populations, finding that the FIM motor subscale was more sensitive to change than the Assessment of Motor and Process Skills in the orthopedic and geriatric groups, but not in the oncology group 6.