Background   Assessing functional status is integral to the care of patients with serious illness. Accurate assessments of a patient’s functional capacity can enable clinicians to better understand a patient’s rehabilitation potential, caregiving needs, and prognosis (1). Validated tools that are relevant to the patient’s clinical situation can provide a more uniform language for clinicians to describe functional capacity (2).  They can also be another tool to guide pain and symptom management (2). A plethora of functional status scales are available in clinical practice. This Fast Fact reviews functional status scales that are most relevant and validated for patients with life-limiting illnesses.

Katz Index of Independence in Activities of Daily Living (ADL)   This tool was developed in the 1970s for evaluating chronically ill patients with lower physical functional status and geriatric patients in the community (3,4). It can be quickly administered via a single question about six domains that are foundational to independent living (bathing, toileting, dressing, feeding, transferring, and continence) (3). It is reliably reproducible with an intraclass correlation (ICC) of 0.91 (5) and requires no specialized training. However, it has low sensitivity and specificity for patients with dementia and Parkinson’s disease in detecting smaller functional changes over time and determining home care needs (6).

Lawton Instrumental Activities of Daily Living (IADL)   Also developed in the 1970s, this tool evaluates more complex functional abilities in outpatients and can be administered over a few minutes by a clinician without specialized training. IADL assesses 8 domains: housekeeping, telephone use, food preparation, financial management, shopping, medication management, laundry, and transportation (7,8). It has shown better sensitivity and specificity than the ADL scale in patients with dementia and for determining home care needs (9). It is reliably reproducible (r=0.85-0.95) (9).

6 Minute Walk Test (6MWT)   6MWT was developed in 2002 and can be administered in office settings. The patient is asked to walk across a stretch of 30 meters for 6 minutes, while their distance, vitals, and symptoms are monitored (11,12). The 6MWT gives a broad assessment of a patient’s cardiorespiratory, musculoskeletal, and vestibular systems. Most data on 6MWT comes from patients with advanced cardiopulmonary diseases such as CHF, COPD, and interstitial lung disease. It has high reproducibility (ICC: 0.97) and can be repeated serially to gauge response to cardiopulmonary rehabilitation (5,13). Lower scores (total distance walked <300 meters) have been associated with lower survival rates in patients who suffered a stroke and in patients with advanced CHF (14,15). 

Karnofsky Performance Status (KPS)   Introduced in 1949, KPS is a commonly used 100-point scale that evaluates functional status in oncology settings (16). It can be administered reliably by a clinician without specialized training (ICC 0.787) and quickly (few minutes) in an office setting (17). It looks at patient’s baseline activity levels, disease related disability, and dependence on caregivers to determine a numerical value of function on a scale of 0-100, with 0 being dead, and 100 no functional limitation (18). A KPS score 50 percent or less predicts a median life expectancy of two months for patients with a progressive underlying cancer (19).

Eastern Cooperative Oncology Group (ECOG) Performance Scale   One of the most used functional assessment tools in oncology, it was derived from KPS for its relative ease of use before being formalized in 1982 by ECOG (20). It is a 5-point global functional scale with 0 set as normal function without limitation and 4 being a moribund functional status. It only takes a few minutes to administer with 3-4 basic questions evaluating dependence on caregivers and ability to walk and perform self-care (20,21). This scale has good inter-operator reproducibility >0.8 (22), but there is growing literature that patient’s self-reported ECOG and clinician ECOG do not always align (23). Of note, most efficacy trials of systemic cancer therapy have been limited to patients with an ECOG of 0 and 1 (20). ECOG ≥ 2 has been correlated with a prognosis of < 3 months in patients on chemotherapy for solid cancers, at least in the pre-immunotherapy era (24-29). In general, there is significant correlation of ECOG status and overall survival for adults receiving chemotherapy for a variety of solid tumors (24-29); but like KPS, it has correlated poorly with prognosis in non-malignant illnesses (20).

Palliative Performance Scale (PPS)   Commonly used in hospice settings or palliative care units, the PPS is a modernized version of KPS that also incorporates oral intake and level of consciousness. It has been shown to be a validated clinical assessment and prognostic tool in patients already identified as having palliative care goals (30). See Fast Fact #125 for more information. 

Edmonton Functional Assessment Tool (EFAT) was introduced in 2001 to evaluate functional status in palliative care inpatient units (31). It is reliable (ICC 0.97) (32), but because it evaluates 10 domains (communication, mental status, respiratory function, pain, mobility, balance, walking, ADLs, fatigue, and motivation), it can take up to 15 minutes for a clinician to complete (31). Therefore, it may be more applicable to research rather than clinical settings. 

Conclusion   Given the association of functional status with quality of life and prognosis, clinicians should routinely implement functional assessment into the clinical care of patients with life-limiting illnesses. While there are insufficient data to broadly recommend any scale, clinicians should be familiar with validated functional assessment scales which can be applied to the relevant underlying illness. 

References:

1. Borras-Fernandez I, Montes-Chinea N, Castillo B, Cruz M. American Academy of Physical Medicine and Rehabilitation. Functional Assessment. May 2, 2016. Updated May 2, 2016. Accessed November 11, 2020. https://now.aapmr.org/functional-assessment/
2. Bierman AS. Functional status: the six vital sign. J Gen Intern Med. 2001;16(11):785-786.
3. Katz S, Downs TD, Cash HR, Grotz RC. Progress in development of the index of ADL. Gerontologist. 1970 Spring;10(1):20-30.
4. Katz Index of Independence in Activities of Daily Living. Alz.org. Accessed November 9, 2020. https://www.alz.org/careplanning/downloads/katz-adl.pdf
5. José A, Dal Corso S. Reproducibility of the six-minute walk test and Glittre ADL-test in patients hospitalized for acute and exacerbated chronic lung disease. Braz J Phys Ther. 2015 May-Jun;19(3):235-42. 
6. Bjornestad A, Tysnes OB, Larsen JP, Alves G. Reliability of Three Disability Scales for Detection of Independence Loss in Parkinson’s Disease. Parkinsons Dis. 2016;2016:1941034. 
7. Lawton MP, Brody EM. Assessment of older people: self-maintaining and instrumental activities of daily living. Gerontologist.1969 Autumn;9(3):179-86.
8. Lawton – Brody Instrumental Activities of Daily Living (I.A.D.L.). Alz.org. Accessed November 9, 2020. https://www.alz.org/careplanning/downloads/lawton-iadl.pdf
9. Mao HF, Chang LH, Tsai AY, Huang WW, Tang LY, Lee HJ, Sun Y, Chen TF, Lin KN, Wang PN, Shyu YL, Chiu MJ. Diagnostic accuracy of Instrumental Activities of Daily Living for dementia in community-dwelling older adults. Age Ageing. 2018 Jul 1;47(4):551-557.
10. Hoeymans N, Wouters ERCM, Feskens EJM et al. Reproducibility of performance‐based and self‐reported measures of functional status. J Gerontol A Biol Sci Med Sci 1997; 52A: M363– M368.
11. 6 Minute Walk Test Instructions. Uthscsa.edu. Accessed November 9, 2020. https://sapepper.barshop.uthscsa.edu/wp-content/uploads/2017/06/6-Minute-Walk-Test-Instructions-and-Score-Sheet.pdf
12. ATS Committee on Proficiency Standards for Clinical Pulmonary Function Laboratories. ATS statement: guidelines for the six-minute walk test. Am J Respir Crit Care Med. 2002 Jul 1;166(1):111-7. 
13. Waatevik M, Frisk B, Real FG, et al. One Year Change in 6-Minute Walk Test Outcomes is Associated with COPD Prognosis. COPD. 2020 Dec;17(6):662-671.
14. Salbach NM, Mayo NE, Higgins J, Ahmed S, Finch LE, Richards CL. Responsiveness and predictability of gait speed and other disability measures in acute stroke. Arch Phys Med Rehabil. 2001 Sep;82(9):1204-12. 
15. Daullxhiu I, Haliti E, Poniku A, et al. Predictors of exercise capacity in patients with chronic heart failure. J Cardiovasc Med (Hagerstown). 2011 Mar;12(3):223-5. 
16. Karnofsky Performance Status Scale Definitions Rating (%) Criteria. National Palliative Care Research Center (NPCRC).Accessed November 9, 2020. http://www.npcrc.org/files/news/karnofsky_performance_scale.pdf
17. Chow R, Bruera E, Temel JS, Krishnan M, Im J, Lock M. Inter-rater reliability in performance status assessment among healthcare professionals: an updated systematic review and meta-analysis. Support Care Cancer. 2020 May;28(5):2071-2078.
18. Schag CC, Heinrich RL, Ganz PA. Karnofsky performance status revisited: reliability, validity, and guidelines. J Clin Oncol. 1984 Mar;2(3):187-93. 
19. Miller RJ. Predicting survival in the advanced cancer patient. Henry Ford Hosp Med. 1991;39(2):81-4.
20. Eastern Performance Status. National Palliative Care Research Center (NPCRC). Accessed November 9, 2020. http://www.npcrc.org/files/news/ECOG_performance_status.pdf
21. Oken MM, Creech RH, Tormey DC, et al. Toxicity and response criteria of the Eastern Cooperative Oncology Group. Am J Clin Oncol. 1982 Dec;5(6):649-55.
22. Taylor AE, Olver IN, Sivanthan T, Chi M, Purnell C. Observer error in grading performance status in cancer patients. Support Care Cancer. 1999 Sep;7(5):332-5. 
23. Bergerot CD, Philip EJ, Bergerot PG, Hsu J, Dizman N, Salgia M, et al. Discrepancies between genitourinary cancer patients’ and clinicians’ characterization of the Eastern Cooperative Oncology Group performance status. Cancer. 2021 Feb 1;127(3):354-358.
24. Ayala Alvarez JC, Trejo Rosales RR, Riera Salas R, et al. Functional status as a determinant prognostic factor for overall survival in adult patients with medulloblastoma treated with chemotherapy and radiotherapy. Ann. Oncol. 2019 Nov:30(Suppl 9):ix21.
25. Takahashi M, Takahashi M, Komine K, et al. The G8 screening tool enhances prognostic value to ECOG performance status in elderly cancer patients: A retrospective, single institutional study. PLoS One. 2017 Jun 22;12(6):e0179694. 
26. Chen WJ, Kong DM, Li L. Prognostic value of ECOG performance status and Gleason score in the survival of castration-resistant prostate cancer: a systematic review. Asian J Androl. 2020 Nov 6 (Online).
27. Argiris A, Li Y, Forastiere A. Prognostic factors and long-term survivorship in patients with recurrent or metastatic carcinoma of the head and neck. Cancer. 2004 Nov 15;101(10):2222-9.
28. Xu Y, Zhang Y, Wang X, Kang J, Liu X. Prognostic value of performance status in metastatic renal cell carcinoma patients receiving tyrosine kinase inhibitors: a systematic review and meta-analysis. BMC Cancer. 2019 Feb 22;19(1):168.
29. Owusu C, Koroukian SM, Schluchter M, Bakaki P, Berger NA. Screening older cancer patients for a Comprehensive Geriatric Assessment: A comparison of three instruments. J Geriatr Oncol. 2011. Apr;2(2):121-129. 
30. Lau F, Downing GM, et al.  Use of Palliative Performance Scale in end-of-life prognostication. Journal of Palliative Medicine 2006; 9(5):1066-1075.
31. Kaasa T, Wessel J. The Edmonton Functional Assessment Tool: further development and validation for use in palliative care. J Palliat Care. 2001 Spring;17(1):5-11. 
32. Kaasa, T, J. Wessel, J. Darrah, E. Bruera. 2000. Inter‐Rater Reliability of Formally Trained and Self‐Trained Raters Using the Edmonton Functional Assessment Tool. Palliative Medicine. 14 (6): 509– 17.

Author Affiliations: Rutgers Robert Wood Johnson Medical School, New Brunswick NJ (MHH); University of Minnesota Medical School, Minneapolis, MN (DAR); University of Pittsburgh Medical Center, Pittsburgh, PA (RA)

Conflicts of Interest:  None which are relevant

Version History: first published electronically in February 2021; originally edited by Sean Marks MD