Linking the LFIS-RA to the ICF
Thirty-five distinct ICF categories from the online classification were linked to the LFIS-RA, which related to Body Structures (n=1, 3%), Body Functions (n=13, 37%), Activities and Participation (n=17, 49%), and Environmental Factors (n=4, 11%) (Table 1). Over half of the ICF categories identified were 2nd level categories (n=18, 51%), followed by 3rd level categories (n=16, 46%) and one 4th level category relating to ‘pain in the lower limb’ (3%). The ICF component that had the most specific categories (higher level) was Activities and Participation, with 13% of concepts being linked to nine 3rd level categories (relating to mobility, undertaking tasks and self-care). This was followed by Body Functions with 8% of concepts being linked to five 3rd level categories (relating to cognitive and muscle function).
Table 1. The number and frequency of ICF categories for each component of the ICF classification that were linked to the LFIS-RA and to concepts derived from PsA-related foot involvement.
ICF components
|
ICF categories linked to
the LFIS-RA
|
ICF categories linked to concepts derived from PsA-related foot involvement
|
|
n (%)
|
Frequency (%)
|
n (%)
|
Frequency (%)
|
Body Structures
|
1 (3%)
|
5 (5%)
|
17 (12%)
|
1127 (15%)
|
Body Functions
|
13 (37%)
|
41 (44%)
|
48 (32%)
|
2656 (35%)
|
Activities and Participation
|
17 (49%)
|
33 (35%)
|
55 (37%)
|
1420 (19%)
|
Environmental Factors
|
4 (11%)
|
15 (16%)
|
28 (19%)
|
2327 (31%)
|
Total
|
35
|
94
|
148
|
7530
|
ICF international Classification of Functioning, Disability and Health, LFIS-RA Leeds Foot Impact Scale in rheumatoid arthritis, PsA Psoriatic arthritis
Agreement analysis
The overall total percentage agreement in the linking of the LFIS-RA to the ICF between the 2 investigators was 77% and the overall kappa statistic was 0.74 (CI 0.67, 0.81). Good levels of interrater agreement were identified across the ICF components in relation to linking to the LFISIF subscale at 0.79 (CI 0.68, 0.89) and the LFISAP subscale at 0.67 (CI 0.55, 0.79). In total 22 additional ICF categories were identified between the investigators, which mostly related to cognitive functions (n=6, 27%) and undertaking tasks (n=5, 23%).
Appraisal of the content validity of the LFIS-RA
Body Structures was the least represented component in the LFIS-RA (3%) with a low frequency of ICF categories relating to the structure of the foot and ankle (n=5, 5%). From the component Body Functions, the most frequent ICF category was b152: Emotional functions (n=11, 12%) and was linked to concepts such as ‘frustrating’, ‘cry’, ‘annoyed’, ‘ashamed’, ‘nervous’, ‘isolated’ and ‘dread’. Pain was covered frequently with descriptors including ‘throb’, ‘hurt’ and ‘burning’ linked to b28015: Pain in the lower limb (n=9, 10%), and discomfort related to ‘pebbles in my shoes’, ‘wakes me up’ and ‘feels heavy’ was linked to other sensory functions. Body Functions representing changes to the spatial-temporal parameters of walking (b770: Gait pattern functions, b455: Exercise tolerance functions) and related dynamic instability (b760: Control of voluntary movement functions) were also frequently cited (Table 2). Activities and Participation was the most represented ICF component in the LFIS-RA (49%) and the most frequent ICF categories were d450: Walking and d230: Carrying out daily routine, which were linked with pain, emotional burden and social withdrawal. The most frequent Environmental Factor was footwear (e1150: n=9, 10%), which was associated with making decisions, walking and self-care activity. In comparison with the most frequent ICF categories linked to PsA-related involvement, the LFIS-RA covered most of the key constructs including pain, functioning, daily activities, footwear restrictions and psychological impact (Table 3).
Table 2. The number and frequency of ICF categories for the components Body Structure and Body Function that were linked to the LFIS-RA.
ICF categories
|
LFIS-RA, n (%)
|
Body Structure
|
-
|
s7502 Structure of ankle and foot
|
5 (100%)
|
Body Function
|
-
|
b152 Emotional functions
|
11 (27%)
|
b28015 Pain in lower limb
|
9 (22%)
|
b770 Gait pattern functions
|
5 (12%)
|
b760 Control of voluntary movement functions
|
3 (7%)
|
b455 Exercise tolerance functions
|
3 (7%)
|
b1801 Body image
|
2 (5%)
|
b1644 Insight
|
2 (5%)
|
b7353 Tone of muscles of lower half of body
|
1 (2.5%)
|
b7800 Sensations of muscle stiffness
|
1 (2.5%)
|
b134 Sleep functions
|
1 (2.5%)
|
b2702 Sensitivity to pressure
|
1 (2.5%)
|
b299 Sensory functions and pain, unspecified
|
1 (2.5%)
|
b279 Additional sensory functions, other specified and unspecified
|
1 (2.5%)
|
ICF international Classification of Functioning, Disability and Health, LFIS-RA Leeds Foot Impact Scale in rheumatoid arthritis, PsA Psoriatic arthritis
Table 3. The number and frequency of ICF categories for the components Activities and Participation, and Environmental Factors that were linked to the LFIS-RA.
ICF categories
|
LFIS-RA, n (%)
|
Activities and Participation
|
-
|
d450 Walking
|
7 (22%)
|
d230 Carrying out daily routine
|
6 (18%)
|
d177 Making decisions
|
3 (9%)
|
d4551 Climbing
|
2 (6%)
|
d4502 Walking on different surfaces
|
2 (6%)
|
d2304 Adapting to changes in daily routine
|
2 (6%)
|
d4552 Running
|
1 (3%)
|
d410 Changing basic body position
|
1 (3%)
|
d570 Looking after one’s health
|
1 (3%)
|
d4154 Maintaining a standing position
|
1 (3%)
|
d920 Recreation and leisure
|
1 (3%)
|
d5402 Putting on footwear
|
1 (3%)
|
d469 Walking and moving, other specified and unspecified
|
1 (3%)
|
d2303 Managing one’s own activity level
|
1 (3%)
|
d4602 Moving around outside the home and other buildings
|
1 (3%)
|
d799 Interpersonal interactions and relationships, unspecified
|
1 (3%)
|
d2202 Undertaking multiple tasks independently
|
1 (3%)
|
Environmental Factors
|
-
|
e1150 General products and technology for personal use in daily living
|
9 (60%)
|
e245 Time-related changes
|
3 (20%)
|
e115 Products and technology for personal use in daily living
|
2 (13%)
|
e399 Support and relationships, unspecified
|
1 (7%)
|
ICF international Classification of Functioning, Disability and Health, LFIS-RA Leeds Foot Impact Scale in rheumatoid arthritis, PsA Psoriatic arthritis
Concepts not covered by the LFIS-RA, that were frequently cited by people with PsA-related foot involvement, were the structure and function of skin to the lower limbs and toenails including related self-care activity, and other musculoskeletal structures such as tendons, muscles and fascia (Table 4). Whilst b1801: Body image was covered in the LFIS-RA (n=2, 2%), it was associated with walking changes and negative emotions but not with other relevant disease-specific constructs in PsA including skin and toenail changes, coping strategies and social withdrawal. The LFIS-RA may underestimate the importance of constructs related to self-management strategies in the context of PsA, with limited coverage of coping styles (0%), self-care activity (n=2, 2%) and accessing healthcare (0%). Participation concepts not fully represented in the LFIS-RA included impact on work (d850) and family relationships (d760).
Table 4. The most frequent ICF categories linked to concepts derived from PsA-related foot involvement for each ICF component and the extent of coverage by the LFIS-RA.
ICF component
|
ICF category
|
Concepts derived from PsA-related foot involvement
|
Percentage coverage by the LFIS-RA, n (%)
|
Body structures
|
s75021: Ankle joint and joints foot and toes
|
‘joints’, ‘ankle joint’, ‘toes’
|
|
|
s8104: Skin of lower extremity
|
‘skin’
|
|
|
s8301: Toenails
|
‘toenails’
|
|
|
s7502: Structure of ankle and foot
|
‘ankle’, ‘heel’, ‘arch’, ‘midfoot’, ‘ball of foot’, ‘forefoot’, ‘sole’
|
5 (100%)
|
|
s75022: Muscles of ankle and foot
|
‘tendons’, ‘Achilles tendon’
|
|
|
S75023: Ligaments and fascia of ankle and foot
|
‘plantar fascia’
|
|
Body functions
|
b28015: Pain in lower limb
|
‘sore’, ‘throbbing’, ‘sharp’, ‘burning’, ‘aching’, ‘severe’, ‘tender’, ‘unbearable’, ‘unpredictable’, ‘constant’
|
9 (22%)
|
|
b152: Emotional functions
|
‘frustrating’, ‘sad’, ‘upset’, ‘embarrassed’, ‘frightening’, ‘envy’, ‘helpless’, ‘depressed’, ‘bad tempered’
|
11 (27%)
|
|
b1801: Body image
|
‘revolting’, ‘ugly’, ‘not normal’, ‘I hate the way they look’, ’disfiguring’, ‘everybody’s eyes goes there’, ‘hide my feet’, ‘I cover up the legs’, ‘don’t want to look outwardly disabled’, ‘it doesn’t feel good’, ‘I don’t want to be noticeable’
|
2 (5%)
|
|
b810: Protective functions of skin
|
‘psoriasis’, ‘hard skin’, ‘thin skin’, ‘dry cracked’, ‘splits’, ‘thick skin’, ‘corn’
|
|
|
b860: Functions of nails
|
‘thick’, ‘lift-up’, ‘hard’, ‘pitting’, ‘split’, ‘thin’, ‘discoloured’, ‘wave-shaped’, ‘break off easily’, ‘build-up under the nail’
|
|
|
b126: Temperament and personality functions
|
‘I like to hide my pain’, ‘if I was in pain I would still force myself to participate’, ‘I just put up with it’, ‘plan for my feet and shoes’
|
|
|
b770: Gait pattern functions
|
‘slower’, ‘limping’, ‘shuffle’, ‘hobbling’
|
5 (12%)
|
Activities and participation
|
d450: Walking
|
‘limited walking activity’, ‘cannot walk barefoot’, ‘painful walking’, ‘cannot walk for long’
|
7 (22%)
|
|
d5702: Maintaining one’s health
|
‘you name it I’ve tried it’, ‘getting advice and getting feet checked’, ‘I can’t actually look under the sole of my foot’, ‘I try to look after myself as much as I can’
|
|
|
d850: Remunerative employment
|
‘unemployed’, ‘I quit my job, because it was mostly you have to stand’, ‘difficulty sitting for long periods at work’, ‘walking at work’, ‘I want to continue working’
|
|
|
d5200: Caring for skin
d5204: Caring for toenails
|
‘moisturising feet’, ‘foot baths’, ‘filing callus’, ‘corns removed’, ‘difficult to cut’, ‘nail polish’, ‘I can’t cut my toenails’
|
|
|
d230: Carrying out daily routine
|
‘can’t do what I want to do’, ‘limits daily activities’, ‘have to keep doing things’, ‘I don't do much’, ‘difficulty with housework’, ‘makes things difficult’, ‘I can’t do a quarter of the stuff I used to do’, ‘I still have to do what I have to do, I just try and rest in between’
|
6 (18%)
|
|
d760: Family relationships
|
‘want to stay healthy for my family and kids’, ‘loss of family time’, ‘burdening the family’, ‘parenting’, ‘affects relationships’, ‘I’m a disappointment to my wife’
|
|
|
d920: Recreation and leisure
|
‘my social life was ruined’, ‘gym’, ‘I used to play soccer’, ‘with my ankle now I can’t exercise’, ‘wedding and formal functions’, ‘stuck at home’, ‘I can’t really go out with friends much’, ‘I don’t like to go out’
|
1 (3%)
|
Environmental factors
|
e1150: General products and technology for personal use in daily living
|
‘difficulty finding nice looking shoes’, ‘unable to find comfortable shoes’, ‘need wide shoes - bigger size’, ‘cannot wear high-heels’, ‘very limited in the type of shoe’, ‘cannot find suitable shoes for work’, ‘wear the same shoes all the time’, ‘can’t wear open shoes’, ‘closed-in’, ‘need a flexible heel-counter’, ‘can’t wear the clothes you want’
|
9 (60%)
|
|
e580: Health services, systems and policies
|
‘accessing podiatry services’, ‘under the care of rheumatology’, ‘delayed diagnosis’
|
|
|
e1151: Assistive products and technology for personal use in daily living
|
‘insoles’, ‘insert’, ‘foot orthotic’
|
|
|
e355: Health professionals
|
‘podiatrist’, ‘rheumatologist’, ‘physiotherapist’, ‘orthopaedic surgeon’
|
|
|
e225: Climate
|
‘summer’, ‘winter’, ‘low-pressure systems’, ‘in summer I find like my foot is quite swollen’
|
|
|
e1101: Drugs
|
‘cortisone injection’, ‘biologics’, ‘pain killers’, ‘steroid creams’
|
|
|
e445: Attitudes of strangers
|
‘other people just don't realise’, ‘feeling judged’, ‘they think I look healthy’, ‘they don't understand how it does affect your life with getting up, walking, just simple things’, ‘there’s just no recognition, understanding or acceptance at all’
|
|
|
e310: Immediate family
|
‘my son has got skin psoriasis…a worse state than mine’, ‘thankfully they’re quite understanding’, ‘they helped me a lot’, ‘supportive’
|
|
ICF international Classification of Functioning, Disability and Health, LFIS-RA Leeds Foot Impact Scale in rheumatoid arthritis, PsA Psoriatic arthritis
Difficulty with linking to the ICF. Three concepts were assigned as not definable referring to quality of life in general; ‘my whole life’ (n=2, 67%) and ‘in the background’ (n=1, 33%). Concepts that were difficult to link to the ICF were related to aspects of time, rest and instability. Although temporal changes associated with pain such as ‘at night’ and ‘end of the day’ were covered in the LFIS-RA and were linked to e245: Time-related changes, other temporal aspects including ‘every time’, ‘all day’ and ‘all the time’ could not be linked to the ICF classification. The concept of rest in the ICF is described as a mental and cardiovascular function, which may not ideally capture the meaning of rest in the context of reduced physical function. Concepts relating to rest in the LFIS-RA such as ‘I have to walk for a bit and sit for a bit’ were linked to b455: Exercise tolerance functions, but reveals deficiencies in the ICF classification. Foot-related instability associated with balance, fear of falling and coordination was linked to b760: Control of voluntary movements. However, instability was difficult to link to a suitable ICF category due to the concept covering various other categories such as stability of joint functions, vestibular and proprioceptive functions, which reflects limitations in the ICF linking process. Coping with PsA-related foot problems was the most frequent concept linked to Personal Factors. Although Personal Factors were not identified in the LFIS-RA, concepts that were covered such as adapting (d2304), planning (d230) and managing activity levels (d2302) could be interpreted as coping strategies if not developed in response to disease impact. This overlap in meaning represents a shortfall of the online ICF classification in defining foot disease burden with possible ambiguity of these concepts reflected as a positive personal attribute or as a negative consequent impairment of the disease.