GMFM: Gross Motor Function Measure, Part I

Kathy McKellar, “Knowledge Broker” January 2007

Based on a presentation by Dianne Russell, CanChild Centre for Childhood Disability Research, Knowledge Broker project co-investigator

KB study Looking at clinical knowledge and

appropriate use of: GMFCS GMFM Motor Growth Curves (MCG’s):

prognosis, treatment planning

Health Condition Health Condition ((disorder/diseasedisorder/disease))

Interaction of ConceptsInteraction of ConceptsICF 2001ICF 2001

Environmental Environmental FactorsFactors

Personal Personal FactorsFactors

Body Body function&structurefunction&structure (Impairment(Impairment))

ActivitiesActivities(Limitation)(Limitation)

ParticipationParticipation(Restriction)(Restriction)

GMFM: Why was it developed? To answer the question: “How do

we measure small but important changes in motor function for children with CP?”

Development started in 1984

GMFM Criterion-referenced test:

evaluates performance of motor skills on that day; useful for comparison over time

Measures how much of a task the child can accomplish, rather than how well the task is completed (quantity, not movement quality)

Who is the GMFM appropriate for? Children with CP: original validation

sample included kids 5 mo- 16 yrs May be appropriate for children

with other diagnoses GMFM is appropriate for children

whose motor skills are at or below those of a typical 5 year old.

GMFM Formats GMFM-88: 88 items GMFM-66: 66 items GMFM-88 with reported scores for

kids with Down Syndrome

Examiner Qualifications For use by pediatric PT’s Before testing children, PT’s should

familiarize themselves with the scoresheet and the administration and scoring guidelines

CD ROM training available

Time required GMFM 88: approx. 45-60 minutes GMFM 66: faster, allows for some

missing data (items that are not tested)

Can be completed in more than 1 session (ideally complete all items within 1 week)

GMFM-8888 items in 5 gross motor dimensions

(for ease of administration): lying and rolling crawling and kneeling Sitting Standing walking, running and jumping

GMFM-66 Same dimensions, but 22 items

eliminated (mostly in lying position)

Validation of the GMFM-88 Reliability

• Test-retest (ICC = 0.99) ( dimensions ranged .92-.99)• Inter-rater (ICC = 0.99) (dimensions ranged .87-.99)

•Validity• Gradient of change: pre-school children without

CP>children with ABI>children with CP

• Children with CP who were young & mild > older & more severe

Validation of the GMFM-88 Change over 6 months as judged by

parents, therapists, and a “masked” video analysis was correlated with change scores on the GMFM-88

Further evidence of reliability & validity Reliability established by others outside the

GMFM team (Bjornson et al. 1994;1998, Nordmark et al. 1997)

Responsiveness (Bjornson et al. 1998; Kolobe et al. 1998

Discriminative validity (Palisano et al 2000)

Why use the GMFM? Reliable, valid Internationally accepted: Translated

into several languages, including Dutch, French, German, Icelandic, Japanese

Considered best practice Used as an outcome measure

Used as an outcome measure Surgery (rhizotomy, pallidal stimulation, muscle

tendon)

Drugs (botulinum toxin, intrathecal baclofen)

Physical therapy (including ambulatory aids & orthoses)

Horseback riding

Strength training & physical fitness

Use of the GMFM in other populations Osteogenesis imperfecta (Ruck-Gibis

et al. 2001)

Lymphoblastic leukemia (Wright et al. 1998)

Down syndrome (Russell et al. 1998)

Validation for children with Down syndrome Compared the results using the

standard scoring method with an alternate method of scoring using caregiver report “Reported Score” (for items which the therapist couldn’t entice the child to demonstrate)

Found stronger evidence of reliability, validity & responsiveness with “reported score”

Equipment GMFM kit Need smooth floor, large firm

exercise mat, toys for motivation, large bench or table for cruising

Five steps with railing Wheeled stool

Environment Room large enough to

accommodate the equipment, the child and the examiner

Private area Consistent environment for

retesting

Clothing Shorts and Tshirt are ideal Testing is done without shoes

Preparing for Testing Have manual, equipment, score

sheet ready. Room booked, mat in place, as

well as other required furniture

Testing Items may be tested in any order,

but be careful not to miss any! (esp. when using the GMFM 88)

Verbal encouragement or demonstration is permitted

Maximum 3 trials for each item Spontaneous performance of any

item is acceptable

Non-compliance Strategies such as “follow the leader” or

role playing can be used Toys and incentives can be used as

motivators (eg. creep through a tunnel) If a child refuses to attempt an item that

you think they can do, return to the item at the end of the test, or try it again in in another session. You can also circle “not tested”.

Scoring the GMFM Scores 0-3 or NT 0- does not intitiate task 1- intitiates task (<10%) 2- partially completes task (10-99 %) 3- completes task (100%) Sometimes generic scoring as

above, other times specific criteria for each level

Scoring the GMFM, cont. The score given is based on the best

performance out of the 3 trials If undecided about what score to assign,

choose the lower of the 2 possible scores Any item that has been omitted or that

the child is unable (or unwilling) to attempt must be indicated as NT

In the GMFM 88, NT items are scored 0, but in the GMFM 66, NT items are treated as missing data

Item 36On the floor: Attains sitting on small bench

0 = does not initiate sitting1 = initiates sitting 2 = partially attains sitting 3 =attains sittingNT = Not tested

Generic Scoring Key

Initiates=completes less than 10% of task

Partially completes= completes >10% to less than 100%

#58: Standing:lifts R foot, arms free, 10 secs.• 0= does not lift R foot, arms free• 1= lifts R foot, arms free, < 3 secs.• 2= lifts R foot, arms free, 3-9 secs.• 3= lifts R foot, arms free, 10 secs.

GMFM Part II… to follow GMFM-88 vs. 66 Scoring GMAE Interpretation of results Motor Growth Curves GMFCS, GMFM, MCG’s: how do

they relate?

Knowledge Broker studyCanChild research project looking at

clinical knowledge and appropriate use of:

GMFCS GMFM Motor Growth Curves (MCG’s)

GMFM Part II Quick review Scoring GMAE Interpretation of results GMFM-88 vs. 66 Motor Growth Curves GMFCS, GMFM, MCG’s: how do they

relate?

GMFM Criterion-referenced test:

evaluates performance of motor skills on that day; useful for comparison over time

Measures how much of a task the child can accomplish, rather than how well the task is completed (quantity, not movement quality)

Who is the GMFM appropriate for? Children with CP: original validation

sample included kids 5 mo- 16 yrs May be appropriate for children with

other diagnoses: osteogenesis imperfecta, lymphoblastic leukemia, Down syndrome

GMFM is appropriate for children whose motor skills are at or below those of a typical 5 year old.

GMFM- 88 and 66GMFM 88: 88 items in 5 gross motor

dimensions: lying and rolling crawling and kneeling Sitting Standing walking, running and jumpingGMFM-66: Same dimensions, but 22 items

eliminated (mostly in lying position)

Scoring of the GMFM 88/66 Math or no math Graph or no graph Computer or no computer

GMFM-88 score: math! Sum the item scores within dimensions

and transfer to the summary score section on the score sheet.

A percent score for each of the 5 dimensions is calculated.

The total percent score for each dimension is averaged to obtain the total score (round off to the nearest whole number)

Scoring with aids/orthotics Use GMFM-88 only First complete the GMFM without the

aid/orthosis, then retest with aid/orthosis For repeat testing at a later dater, apply

the same aid at the same item number Aids/orthoses could have positive and

negative effects Mark an “A” for the aided score on the

score sheet

GMFM-88 - scoring issues (i)

Scoring leads to an overall % score as well as dimension % scores

Change scores: T2 - T1 = GMFM score Assumes that all % changes/unit of time

have the same meaning… ...but we don’t really know what a ‘unit’

of change means clinically! (Some changes might be easier to attain than others)

GMFM-88 - scoring issues (ii) GMFM-88 scaling is ‘ordinal’ (ordered) Cannot assume that a unit of change

has the same meaning across the scale

Really need ‘interval’ scaling, whereby a ‘unit’ of change has the same meaning throughout the scale

Hence the need for Rasch (item-response) analysis

What is Rasch Analysis? It is a way to analyse data to

assess the ‘fit’, order and relative difficulty of items that measure a construct (e.g., GMF)

RASCH SCALING OF THE GMFM Identified items which did not “fit” the

unidimensional construct- eliminated 22 items (GMFM-66)

Items are now arranged in order of difficulty (empirical)

Response options within items are weighted according to difficulty

Interval scale…so that a unit of change has the same meaning across the scale (thus improving the interpretability of scores)

GMFM-66 Only 66 items administered

(asterixed on score sheet) Enter scores into the computer

program: Gross Motor Ability Estimator (GMAE)

Not possible to calculate the score with pencil and paper

Gross Motor Ability Estimator (GMAE)

User-friendly program to analyze GMFM-66 scores with a built-in tutorial

Allows entry of data in two formats:1. Research - from ASCII files or text only

files (files entered into a statistical package –SPSS)

2. Individual GMFM-66 item scores for one or more children

Why use a computer program to score?

Provides an estimate of a child’s score even when not all items have been administered

Provides a database to keep child information and track GMFM-66 scores over time- case summary report

Produces item maps- arrange items by order of difficulty

It’s easy! No math, but graphs!

The GMFM-66 score is an interval-level measure of function where subjects are placed on an ability continuum ranging from 0 (low motor ability) to 100 (high motor ability).

Interval level scoring makes comparisons of change over time more meaningful because a difference of, for example, 10 points means the same whether the child is at the lower end or the upper end of the scale.

What is the GMFM-66 score?

Case Summary Report Summarizes demographic data Summarizes score, including error

(standard error and 95% confidence interval)

Graphs scores over time

Item Maps By item order or by difficulty order-

by difficulty order is the most useful

 

                    

Lower Motor GMFM-66 Score with 95% Confidence Intervals Higher Motor Ability Ability

Clinical Use of Item Maps and Case Summaries

• understand/interpret change

• identify relatively easier and more difficult ‘next steps’ for a child

• discuss and communicate a child’s progress

• set appropriate goals and plan interventions

Interpretation of GMAE print-outs

Group exercise

Questions for groups: What is the child’s GMFM-66

score? Are there any unexpected scores? What would you expect the child to

accomplish next? What activities might you work on

in PT with this child?

GMFM 88 and 66 Good reasons to choose one or the

other.

GMFM-88 & GMFM-66General Issues Items are administered and scored the

same, with the exception of a new category of ‘Not Tested’ (NT) to differentiate a true “0” from an item not attempted

If administer the GMFM-88 with NT, the data can also be used to calculate score for GMFM-66

Strengths of GMFM-88 Reliable and valid measure of change

over time in children with CP and children with Down syndrome

Widely used in practice and research GMFM is most responsive to change

in children with CP under age 5 years

Limitations of GMFM-88 Time to administer

- all items must be administered

Must give a score of “0” for items if the child refuses or assessor fails to administer

Score based on number of items completed regardless of difficulty

When should I use the GMFM-88? For a more detailed description of skills

especially for children whose skills are primarily in Lying and Rolling activities (e.g., infants, or children classified at GMFCS Level V)

No access to a computer Assessing effects of aides and orthoses Assessing children with diagnosis other

than CP

Strengths of GMFM-66 Reliable and valid measure of change

over time in children with CP Items are ordered by difficulty A score can be derived with a less-than-

complete assessment Item maps useful in understanding

motor function and in planning goals Computer program allows tracking of

individual children’s scores over time

Possible Limitations of GMFM-66 Requires use of a computer

program for scoring

May need some time to learn how to interpret item maps

No longer able to calculate dimension scores

When should I use the GMFM-66? Assessing children with cerebral palsy

where the interval properties of the scale are important (e.g. Research purposes, change over time)

When you have limited time to administer all items

Access to a computer and the GMAE scoring program

Motor Growth Curves More graphs!

Motor Growth Curves Derived from a longitudinal study 657 children, >2600 GMFM

assessments Children <6 years assessed every

6 mo., older children assessed every 9-12 mo.

Plotted GMFM-66 score against age

Longitudinal Motor Growth Curves for Children with Cerebral Palsy by GMFCS Level Using GMFM-66 (N=2624 observations)

How can the Motor Growth Curves be used?

• Describe patterns of gross motor function for children with cerebral palsy over time

• Estimate a child’s future motor capabilities (prognosis)

• Compare child’s GMFM-66 score with children in the sample of a similar age and severity

GMFM-66 plateau Does not mean therapy is not

needed!

Work on quality, functional goals, equipment needs, prevention of secondary problems.

Putting the measures all together…..• Several different purposes :

discriminative (descriptive) evaluative prognostic (predictive)

• Can be used together to track and evaluate change over time and determine how the rate of change compares to children of similar abilities and ages

Case Study

• Beth

Use of Motor Measures at QA How could these measures work

for us?

*** Most useful if used by all PT’s, in both EIP and SAP