Functional Status Score for the Intensive Care Unit

Last Updated

September 12, 2022

Purpose

The Functional Status Score for the Intensive Care Unit (FSS-ICU) is a 5-item performance-based measure that utilizes an 8 point, ordinal scale to measure physical function for patients in the intensive care unit setting. The FSS-ICU examines the patient’s ability to perform the following five tasks: rolling, transfer from supine to sit, sitting at the edge of bed, transfer from sit to stand, and walking. Additionally, there is a baseline version of the FSS-ICU that can be performed retrospectively via phone by proxy.

Link to Instrument

Instrument Details

Acronym FSS-ICU

Area of Assessment

Functional Mobility

Assessment Type

Performance Measure

Administration Mode

Paper & Pencil

Cost

Free

CDE Status

Not a CDE--last searched 10/30/2024

Mixed Populations

5 items are performed: rolling, transfer from supine to sit, sitting at the edge of bed, transfer from sit to stand, and walking
Each task is evaluated using an eight-point ordinal scale ranging from 0 (unable to perform) to 7 (complete independence)
Item scores are summed
The total score ranges from 0-35, with higher scores indicating better physical functioning.

Number of Items

Scoring Sheet
Pen
Chair

10-30 minutes

Depending on the patient’s functional status; can be incorporated as part of a routine physical therapy session with minimal to no additional time required

Required Training

Reading an Article/Manual

Required Training Description

Written guidelines, frequently asked questions document, pocket card and training video available at https://www.improvelto.com/instruments/ (free registration required to access)

Adults

18 - 64

years

Elderly Adults

65 +

years

Instrument Reviewers

Heather Littier PT, DPT, MS; Stephanie Hiser PT, DPT, CCS; Bronwen Connolly, MSc, PhD, MCSP; and Dale Needham, MD, PhD, Johns Hopkins University

ICF Domain

Body Function
Activity

Measurement Domain

Motor

Professional Association Recommendation

None found--last searched 10/30/2024

Considerations

•   Developed for use with patients in the intensive care unit
•   May take extra time depending on patient acuity and presentation
•   If ≤2 tasks were not performed, use the average score from the completed items to score the 1 or 2 missing tasks
•   If >2 tasks were not performed, an overall FSS-ICU score cannot be calculated
•   The FSS-ICU should be used to grade the patient’s physical performance only
•   Unless otherwise stated, scoring of the FSS-ICU should be based on only one evaluator physically assisting/supervising the patient.
•   Scoring of the FSS-ICU must be completed without the use of a patient lift device
•   Scoring should be based on what is performed during the session, rather than what the patient is capable of or what has been previously performed

Standard Error of Measurement (SEM)

ICU Patients: (Huang et al., 2016; n = 819 (USA1 = 34, USA2 = 59, Australia = 66, Brazil1 = 99, Brazil2 = 561); Mean Age = 70 (SD = 13 years); male = 387 (47%), Portuguese translation of FSS-ICU for Brazilian data sets)

SEM for ICU awakening/admission (n = 807): 1.3
SEM for ICU discharge (n = 800): 2.4
SEM for Hospital discharge (n = 91): 1.9

ICU Patients: (Alves et al., 2019; n = 100; mean age = 72 (16) years)

SEM for ICU discharge (n = 100): 0.54

Minimal Detectable Change (MDC)

ICU patients: (Huang et al., 2016; n = 819)

MDC for ICU awakening/admission (n = 807): 3.1
MDC for ICU discharge (n = 800): 5.4
MDC for hospital discharge (n = 91): 4.5

ICU Patients: (Alves et al., 2019)

MDC90 for ICU admission (n = 100): 1.0

ICU Patients: (Richtrmoc et al., 2020; n = 40; mean age = 55.15 (19.16); male = 26 (65%); Brazilian Portuguese translation of FSS-ICU)

MDC for ICU discharge (n = 40): 2.9

Minimally Clinically Important Difference (MCID)

ICU Patients: (Huang et al., 2016; n = 819)

MCID for ICU patients estimated at 2.0 - 5.0

ICU Patients: (Thrush & Steenbergen, 2022; n = 2793, mean age = 57 (IQR = 44-70), male = 62%, median length of stay = 14 days (IQR = 8-28))

MCID for all ICU patients (n = 2793): 3.9
MCID for stroke patients (n = 644): 4.2
MCID for cardiovascular patients (n = 642): 1.8
MCID for medical patients (n = 554): 4.2

Test/Retest Reliability

General Intensive Care Unit: (Alves et al. 2019; n = 100; mean age = 72 (SD = 16 years))

Excellent test-retest reliability: (ICC = 0.99)

Medical-Surgical Intensive Care Unit: (González-Seguel et al. 2020; n = 6; age > 18 w/invasive mechanical ventilation during hospitalization, Chilean-Spanish translation of FSS-ICU)

Excellent test-retest reliability: (ICC = 0.96)

Medical Intensive Care Unit: (Do et al. 2021, n = 31)

Excellent test-retest reliability: (ICC = 0.98)

Interrater/Intrarater Reliability

Surgical Intensive Care Unit: (Hiser et al., 2018; n = 81 (Surgical ICU = 27, Medical ICU = 34, Neurological ICU = 20); mean age = 64 (IQR = 56-71); female = 33 (43%))

Excellent interrater reliability for Surgical ICU (n = 27): (ICC = 0.984)
Excellent interrater reliability for Medical ICU (n = 34): (ICC = 0.987)
Excellent interrater reliability for Neurological ICU (n = 20): (ICC = 0.977)
Excellent Interrater reliability for combined ICU's (n = 81): (ICC = 0.985)

General Intensive Care Unit: (Ragavan et al., 2016; n = 26; mean age = 54 (20) years; female = 14 (54%))

Excellent interrater reliability: (ICC = 0.99)

Coronary Intensive Care Unit: (Kahraman et al., 2019; n = 50; mean age = 69 (12) years; male = 34 (68%); Turkish translation of FSS-ICU)

Excellent interrater reliability for total score and functional tasks: (ICC's = 0.955-0.993)
Excellent Intrarater reliability for total score and functional tasks: (ICC's = 0.976-0.996)

General Intensive Care Unit: (Silva et al., 2017; n = 30; mean age = 56 (14); male = 15 (50%); Brazilian Portuguese translation of FSS-ICU)

Excellent interrater reliability: (ICC = 0.88)

General Intensive Care Unit: (Alves et al., 2019)

Excellent interrater reliability: (ICC = 0.96)

Medical Intensive Care Unit: (Do et al., 2021)

Excellent interrater reliability: (ICC = 0.99)

Medical-Surgical Intensive Care Unit: (Gonzalez-Seguel, et al. 2022; n = 6; age > 18 w/invasive mechanical ventilation during the current hospitalization; Chilean-Spanish translation of FSS-ICU)

Excellent interrater reliability: (ICC = 0.96)

Internal Consistency

Intensive Care Unit: (Huang et al., 2016; n = 819)

Adequate to Excellent: Cronbach's alpha range range across five studies = 0.78-0.95

General Intensive Care Unit: (Ragavan et al., 2016; n = 26)

Excellent: Cronbach's alpha for total score = 0.99

Coronary Intensive Care Unit: (Kahraman et al., 2019; n = 50)

Excellent: Cronbach’s alpha for total score = 0.95

General Intensive Care Unit: (Alves et al., 2019; n = 100)

Excellent: Cronbach’s alpha for total score = 0.95

Medical Intensive Care Unit: (Do et al., 2021; n = 31)

Excellent: Cronbach's alpha = 0.90

Criterion Validity (Predictive/Concurrent)

Predictive validity:
Intensive Care Unit: (Huang et al., 2016)

For each 1-point increase in FSS-ICU score at ICU discharge, post hospital length of stay decreased by 0.27 days in the combined results (p < 0.01; n = 136)
For each 1-point increase in FSS-ICU score at ICU discharge, the odds of discharge home increased by 11% in the combined results (p <0.01; n = 135)
Adequate predictive ability of the FSS-ICU to predict discharge location for the combined results (AUC = 0.75)

Intensive Care Unit: (Tymkew et al., 2020; n = 1203, all ICU's at a large academic hospital)

A FSS-ICU score at initial assessment of 16 or greater predicted discharge home (sensitivity 71.8%; specificity 73.6%; AUC=0.69)
A FSS-ICU score at ICU discharge of 19 or higher predicted discharge home (sensitivity 82.9%; specificity 73.6%; AUC=0.80)
A FSS-ICU score at hospital discharge of 22 or greater predicted discharge home (sensitivity 80.3%; specificity 79.7%; AUC=0.85)

Construct Validity

Convergent validity:

Intensive Care Unit:

Prehospitalization: (Huang et al., 2016; n = 78-82)

Adequate validity of the FSS-ICU performed prehospitalization with instrumental activities of daily living (r = 0.55)
Excellent validity of the FSS-ICU performed prehospitalization with activities of daily living (r = 0.80)

ICU Awakening/Admission: (Huang et al., 2016; n = 20-802)

Adequate validity of the FSS-ICU at ICU awakening/admission with activities of daily living (r = 0.39)
Adequate validity of the FSS-ICU at ICU awakening/admission with manual muscle test score (r = 0.44)
Adequate validity of the FSS-ICU at ICU awakening/admission with hand grip % predicted strength (r = 0.40)
Adequate validity of the FSS-ICU at ICU awakening/admission with hand grip strength (r = 0.37)
Adequate validity of the FSS-ICU at ICU awakening/admission with the ICU Mobility Scale (r = 0.46)

ICU Awakening/Admission: (Parry et al., 2015; n = 66, mean age = 58 (17), male = 40 (61%))

Excellent validity of the FSS-ICU at ICU awakening/admission with Physical Function in Intensive Care Test (PFIT-s) (r = 0.87)
Adequate validity of the FSS-ICU at ICU awakening/admission with Medical Research Council Sum Score (MRC-SS) (r = 0.69)

ICU Awakening/Admission: (Camus-Molina et al., 2020; n = 30, 25th and 75th percentiles = 55 & 74, mechanically ventilated patients > 18 years old, Chilean-Spanish translation of FSS-ICU)

Excellent validity of the FSS-ICU at ICU awakening/admission with cumulative inactivity time (accelerometer data) (r = -0.62)
Excellent validity of the FSS-ICU at ICU awakening/admission with MRC-SS (r = 0.67)
Excellent validity of the FSS-ICU at ICU awakening/admission with ICU length of stay (r = -0.70)
Excellent validity of the FSS-ICU at ICU awakening/admission with time on mechanical ventilation (r = -0.60)

ICU Discharge: (Huang et al., 2016; n = 27-800)

Excellent validity of the FSS-ICU at ICU discharge with activities of daily living (r = 0.60)
Excellent validity of the FSS-ICU at ICU discharge with manual muscle test score (r = 0.60)
Adequate validity of the FSS-ICU at ICU discharge with hand grip % predicted strength (r = 0.50)
Adequate validity of the FSS-ICU at ICU discharge with hand grip strength (r = 0.59)
Excellent validity of the FSS-ICU at ICU discharge with the ICU Mobility Scale (r = 0.86)
Poor validity of the FSS-ICU at ICU discharge with ICU length of stay (r = -0.25)

ICU Discharge: (Parry et al., 2015; n = 66)

Excellent validity of the FSS-ICU at ICU discharge with PFIT-s (r = 0.85)

ICU Discharge: (Alves et al., 2019; n = 100)

Excellent validity of the FSS-ICU at ICU discharge with FIM motor domain score (r = 0.94)

During ICU Stay: (Do et al. 2021, n = 31)

Excellent validity of the FSS-ICU during ICU stay with Johns Hopkins Highest Level of Mobility Scale (r = 0.63)
Excellent validity of the FSS-ICU during ICU stay with Activity Measure for Post-Acute Care - Basic Mobility Inpatient Short Form (r = 0.90)
Excellent validity of the FSS-ICU during ICU stay with MRC-SS (r = 0.63)

ICU Discharge: (Camus-Molina et al., 2020; n = 30)

Excellent validity of the FSS-ICU at ICU discharge with cumulative inactivity time (accelerometer data) (r = -0.79)
Excellent validity of the FSS-ICU at ICU discharge with MRC-SS (r = 0.72)
Excellent validity of the FSS-ICU at ICU discharge with ICU length of stay (r = -0.77)
Excellent validity of the FSS-ICU at ICU discharge with time on mechanical ventilation (r = -0.62)

ICU Discharge: (Dos Reis et al., 2021; n = 122, median age = 56 (IQR = 47-66, male = 62 (51%), inclusion criteria: completion of a 48-hour stay in ICU and written informed consent by participant or family member, Brazilian Portuguese translation of FSS-ICU)

Excellent validity of the FSS-ICU at ICU discharge with Early Rehabilitation Barthel Index (r = 0.77)

ICU Discharge: (Dos Reis et al., 2022; n = 122, median age = 56 (IQR = 47-66, male = 62 (51%), inclusion criteria: completion of a 48-hour stay in ICU and written informed consent by participant or family member, Brazilian Portuguese translation of FSS-ICU)

Excellent validity of the FSS-ICU at ICU discharge with Barthel Index (r = 0.88)

Hospital Discharge: (Huang et al., 2016; n = 31-91)

Excellent validity of the FSS-ICU at Hospital discharge with activities of daily living (r = 0.80)
Excellent validity of the FSS-ICU at Hospital discharge with manual muscle test score (r = 0.80)
Adequate validity of the FSS-ICU at Hospital discharge with hand grip % predicted strength (r = 0.43)
Adequate validity of the FSS-ICU at Hospital discharge with hand grip strength (r = 0.49)
Poor validity of the FSS-ICU at Hospital discharge with hospital length of stay (r = -0.26)

Coronary Intensive Care Unit: (Kahraman et al., 2019; n = 50)

Excellent validity of the FSS-ICU at ICU evaluation with handgrip strength for right (r = 0.767) and left (r = 0.764) hands
Excellent validity of the FSS-ICU at ICU evaluation with knee extension strength for right (r = 0.707) and left (r = 0.701) knees
Excellent validity of the FSS-ICU at ICU evaluation with the Perme ICU Mobility Score (r = 0.92)
Excellent validity of the FSS-ICU at ICU evaluation with the Katz ADL Score (r = 0.80)

Discriminant validity:

Prehospitalization: (Huang et al., 2016; n = 78-82)

Excellent discriminant validity between the prehospitalization FSS-ICU and body mass index (r = -0.03)
Excellent discriminant validity between the prehospitalization FSS-ICU and the continence item from activities of daily living (r = 0.03)

ICU Awakening/Admission: (Huang et al., 2016; n = 20-147)

Excellent discriminant validity between the FSS-ICU at ICU awakening/admission and body mass index (r = -0.01)
Adequate discriminant validity between the FSS-ICU at ICU awakening/admission and the continence item from activities of daily living (r = 0.50)

ICU Discharge: (Huang et al., 2016; n = 20-147)

Excellent discriminant validity between the FSS-ICU at ICU discharge and body mass index (r = 0.05)
Poor discriminant validity between the FSS-ICU at ICU discharge and the continence item from activities of daily living score (r = 0.70)
Excellent discriminant validity between the FSS-ICU at ICU discharge and hemodialysis status (r = -0.20)
Excellent discriminant validity between the FSS-ICU at ICU discharge and steroid use (r = 0.19)
Excellent discriminant validity between the FSS-ICU at ICU discharge and insulin use (r = 0.11)

Hospital Discharge: (Huang et al., 2016; n = 31-91)

Excellent discriminant validity between the FSS-ICU at hospital discharge and body mass index (r = -0.05)
Adequate discriminant validity between the FSS-ICU at hospital discharge and the continence item from activities of daily living (r = 0.42)
Adequate discriminant validity between the FSS-ICU at hospital discharge and hemodialysis status (r = 0.38)
Excellent discriminant validity between the FSS-ICU at hospital discharge and need for home oxygen (r = 0.05)
Excellent discriminant validity between the FSS-ICU at hospital discharge and steroid use (r = -0.16)
Excellent discriminant validity between the FSS-ICU at hospital discharge and insulin use (r = -0.06)

3^rd Day During ICU stay: (Kahraman et al., 2019; n =50)

Excellent discriminant validity between the FSS-ICU at 3^rd day during ICU stay and body mass index (r = -0.07)
Excellent discriminant validity between the FSS-ICU at 3^rd day during ICU stay and heart rate (r = -0.24)
Excellent discriminant validity between the FSS-ICU at 3^rd day during ICU stay and systolic blood pressure (r = 0.12)
Excellent discriminant validity between the FSS-ICU at 3^rd day during ICU stay and diastolic blood pressure (r = 0.21)

Content Validity

No explicit testing done; FSS-ICU was designed by a multi-disciplinary team with expertise in physical functioning assessment in critically ill patients and was modelled on relevant aspects of a physical therapy assessment.

Floor/Ceiling Effects

Intensive Care Unit: (Parry et al., 2015)

Adequate floor effect of 3.0% at ICU awakening
Excellent: no floor effect at ICU discharge
Excellent: no ceiling effect at ICU awakening
Adequate ceiling effect of 3% at ICU discharge

Intensive Care Unit: (Huang et al., 2016)

Excellent: no floor effect at hospital discharge
Adequate floor effects of 0.5% at ICU admission/awakening and 0.3% at ICU discharge
Adequate ceiling effects of 0.7% at ICU admission/awakening and 11% at ICU discharge
Poor ceiling effect of 21% at hospital discharge

Intensive Care Unit: (Alves et al., 2019)

Excellent: no floor effect at ICU admission
Adequate ceiling effect of 16% at ICU admission

Intensive Care Unit: (Camus-Molina et al., 2020)

Excellent: no floor effect at ICU awakening
Excellent: no floor effect at ICU discharge
Excellent: no ceiling effect at ICU awakening
Adequate ceiling effect of 10% at ICU discharge

Intensive Care Unit: (Thrush et al, 2022)

Adequate floor effect of 3.2% for whole group at ICU admission
Adequate floor effect of 1.4% for whole group at ICU discharge
Adequate floor effect of 3.4% for whole group at ICU admission
Poor ceiling effect of 23% for whole group at ICU discharge

Intensive Care Unit: (Richtrmoc, et al., 2020)

Excellent: no floor effects at admission or discharge
Poor ceiling effects of 50% at admission and 70% at discharge

Coronary Intensive Care Unit: (Kahraman et al 2019)

Excellent: no floor effect on day 3 of ICU admission
Adequate ceiling effect of 6% on day 3 of ICU admission

Responsiveness

Intensive Care Unit: (Huang et al, 2016) Assessed at baseline (prior to hospitalization; n = 806), ICU admission/awakening (n = 662), ICU discharge (n = 71), and hospital discharge (n = 73)

Statistically significant, positive changes between each consecutive time point were found (p < 0.01)
Median FSS-ICU score (range: 0 to 35) was 35 (IQR = 33-35) prior to admission, 5 (IQR = 5-10) at ICU admission/awakening, 20 (IQR = 10-30) at ICU discharge, and 29 (IQR = 20-34) at hospital discharge.
The effect size was 2.02 from ICU awakening/admission to ICU discharge

Intensive Care Unit: (Richtrmoc et al, 2020) Assessed at ICU admission/awakening (n = 40) and ICU discharge (n = 40)

Significant increase of 3.9 (95% CI: 1.75-6.05) points on FSS-ICU from admission to discharge (p < 0.001)
Median FSS-ICU score was 28.7 (9.1) at ICU admission and 32.6 (5.0) at ICU discharge (p = 0.001)
Moderate effect size of 0.53 from ICU admission to ICU discharge

Intensive Care Unit: (Thrush et al, 2022) Assessed at ICU admission and discharge (n = 2793)

Effect size for all patients (n = 2793): 0.87
Effect size for stroke patients (n = 644): 0.93
Effect size for cardiovascular patients (n = 642): 2.60
Effect size for medical patients (n = 554): 0.61

Bibliography

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Camus-Molina A, Gonzalez-Seguel F, Castro-Avila A, Leppe J. Construct Validity of the Chilean-Spanish Version of the Functional Status Score for the Intensive Care Unit: A Prospective Observational Study Using Actigraphy in Mechanically Ventilated Patients. Arch Phys Med Rehabil. 2020;101(11):1914-1921. http://doi.org/10.1016/j.apmr.2020.04.019

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Parry, S. M., Denehy, L., Beach, L. J., Berney, S., Williamson, H. C., & Granger, C. L. (2015). Functional outcomes in ICU–what should we be using?-an observational study. Critical Care, 19(1), 127. https://doi.org/10.1186/s13054-015-0829-5

Ragavan, V. K., Greenwood, K. C., & Bibi, K. (2016). The Functional Status Score for the Intensive Care Unit Scale: Is It Reliable in the Intensive Care Unit? Can It Be Used to Determine Discharge Placement? Journal of Acute Care Physical Therapy, 7(3):93-100.

Richtrmoc, M., Leite, W. S., Azevedo, A. M., et al. (2020). Effect of early mobilization on respiratory and limb muscle strength and functionality of nonintubated patients in critical care: A feasibility trial. Critical Care Research and Practice, Volume 2020(Article ID 3526730). https://doi.org/10.1155/2020/3526730

Silva, V. Z., Araujo Neto, J. A., Cipriano Jr., G, et al. (2017). Brazilian version of the Functional Status Score for the ICU: translation and cross-cultural adaptation. Rev Bras Ter Intensiva, 29(1):34-38.

Thrush, A. & Steenbergen, E. (2022). Clinical properties of the 6-clicks and Functional Status Score for the ICU in a hospital in the United Arab Emirates. Arch Phys Med Rehabil., 103: 2404-2409. https://doi.org/10.1016/j.apmr.2022.04.008

Tymkew, H., Norris, T., Arroyo, C., & Schallom, M. (2020). The use of physical therapy ICU assessments to predict discharge home. Crit Care Med., 48(9): 1312-1318. https://doi.org/10.1097/CCM.0000000000004467