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Gross Motor Function Measure- 66

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Purpose

The Gross Motor Function Measure (GMFM) is a standardized observational instrument designed to measure change in gross motor function over time in children with cerebral palsy. The GMFM assesses motor function (how much of a task the child can do) rather than the quality of the motor performance (how well the child performs the task).  The GMFM-88 is the original version, and tests 88 items.  The GMFM-66 is a newer version, which was reduced to 66 items by Rasch Analysis.

 

Acronym GMFM

Area of Assessment

Upper Extremity Function

Administration Mode

Computer

Cost

Not Free

Actual Cost

$119.00

Cost Description

$119- for the manual; The computer program GMAE is free. It is available on the website of canchild.ca
https://canchild.ca/en/resources/191-gross-motor-ability-estimator-gmae-2-scoring-software-for-the-gmfm
(“Gross Motor Ability Estimator (GMAE-2) Scoring Software for the GMFM”, n.d.).

Populations

Cerebral Palsy

Key Descriptions

  • GMFM-66 is an observational scale; A therapist can provide a verbal encouragement or demonstrate the item to be tested. A maximum of three trials are permitted and any spontaneous performance is accepted.
  • GMFM- 66 assesses five dimensions-
    Dimension A: Lying and rolling,
    Dimension B: Sitting,
    Dimension C: Crawling and kneeling,
    Dimension D: Standing,
    Dimension E: Walking, running and jumping.
  • Scores range from 0-3, higher scores denote better performance.
    There is a 4-point scoring system for each item on the GMFM.

    0 Does not initiate task
    1 Initiates task (<10%)
    2 Partially completes task (10-99%)
    3 Completes task (100%)
    NT Not tested
  • GMAE software is used for the scoring and interpreting the scores on GMFM-66. It converts the ordinal scale to interval scale improving the accuracy for estimating the child’s performance.
  • The data is entered individually as per the item. GMAE calculates a child’s GMFM-66 score and plots it on an item map along with the 95% confidence intervals (CIs) around the score. The program also allows users to track a child’s progress over time.
  • The data is entered individually as per the item. GMAE calculates a child’s GMFM-66 score and plots it on an item map along with the 95% confidence intervals (CIs) around the score. The program also allows users to track a child’s progress over time.
  • GMFM user’s manual available for scoring and interpreting data for GMFM-66 and GMFM-88.

Number of Items

66 items, which are divided among five dimensions:
Dimension A: Lying and rolling- 4 items,
Dimension B: Sitting- 15 items
Dimension C: Crawling and kneeling- 10 items
Dimension D: Standing- 13 items,
Dimension E: Walking, running and jumping- 24 items.

Equipment Required

  • Mat
  • Adjustable Bench
  • Tape Lines
  • Stairs with 5 steps or more
  • A computer should be accessible

Time to Administer

45-60 minutes

GMFM-66: enter the scores into the computer program “Gross Motor Ability Estimator (GMAE)” for analysis. It is required for use to calculate the total score and item map and also provides additional information including Standard error of measurement (SEM), progress of the child in the form of motor growth curves, and percentiles stratified by age and level of Gross motor functional classification scale (GMFCS).

Required Training

Reading an Article/Manual

Age Ranges

Infant

0 - 2

years

Toddler

2 - 5

years

Child

6 - 12

years

Instrument Reviewers

Jinali Shah, PT

ICF Domain

Activity

Measurement Domain

Motor

Considerations

  • GMFM is a comprehensive evaluation of foundational gross motor skills. It has a good reliability and validity for the assessment of gross motor functions for children with cerebral palsy. It covers a wide range age group- 5 years to 16 years. It is user-friendly.
  • GMFM-66 is found to be more sensitive and consistent with the therapist’s judgement of change than GMFM-88 (Adair, Said, & Morris, 2012).
  • GMFM-66 uses a computer program which not only saves time but also provides a focused information regarding the child’s impairments and can also track child’s progress.
  • The most frequently used function of the GMAE for GMFM-66 was the total score option, followed by case summary, item maps, Confidence interval (CI), percentiles and SEM (Standard error of measurement).

Cerebral Palsy

back to Populations

Minimally Clinically Important Difference (MCID)

(Oeffinger et al., 2008, n= 381 children with cerebral palsy of GMFCS levels I-III, age range= 4-18y, mean age 11y; 265 diplegia, 116 hemiplegia; 230 males, 151 females, nonsurgical (n=292) and surgical (n=87) groups at GMFCS Levels I to III.)

 

GMFCS level

MCID medium ES (0.5)

MCID large ES (0.8)

I (n=141)

1.7

2.7

II (n=96)

1.0

1.5

III (n=55)

0.7

1.2

Overall (n=292)

0.8

1.3

Cut-Off Scores

(Eun-Young & Won-Ho, 2015, n= 217, age range= 3-17y.)

The cut-off values determine the percentage of the total score of GMFM-66 scale, below which the sensitivity and the specificity of the test for a particular GMFCS level decreases.

GMFCS Level

GMFM cut-off value (%)

I (n=33)

81.48

II (n=29)

75.98

III (n=24)

53.33

IV (n=31)

40.92

V (n=100)

Not determined

Normative Data

(Eun-Young & Won-Ho, 2015).

GMFCS Level

GMFM mean score (%)

I (n=33)

92.65±8.97

II (n=29)

81.88±18.30

III (n=24)

65.60±18.36

IV (n=31)

44.28±21.88

V (n=100)

22.48±19.36

 p value

<0.001

Test/Retest Reliability

(Bjornson, Graubert, & Mclaughlin, 2000, n=21, age range= 4.4 to 17.7 y; spastic diplegic: n= 13; spastic quadriplegic: n=8.)

  • Excellent test- retest reliability (ICC =0.80–1.00; for all 5 dimensions and total score).

Interrater/Intrarater Reliability

 (Mahasup, Sritipsukho, Lekskulchai, & Keawutan, 2011, n=10, age range= 2-10y.)

  • Excellent interrater reliability (ICC= 0.93)
  • Excellent intrarater reliability (ICC= 0.99-1.00)

Internal Consistency

(McCarthy et al., 2002, n=115, age range= 3.1- 10.4 y.)

  • Excellent: Cronbach’s α coefficient= 0.99

Construct Validity

(Bjornson, Graubert, Buford, & McLaughlin,1998, n=37, age range= 3.2-18.1 y.) In terms of total scores of GMFM-66

  • Excellent correlation with clinicians rating post SDR for dimension B-E (Spearman’s coefficient= 0.72-0.88, p <0.001)
  • Adequate correlation with clinicians rating post SDR for dimension A (Spearman’s coefficient= 0.39, p=0.02)

 

(McCarthy et al., 2002) In terms of total scores for GMFM-66

  • Excellent correlation with mobility domains of Pediatric Evaluation of Disability Inventory (PEDI) (Spearman’s coefficient= 0.91, p<0.0001)
  • Excellent correlation with selfcare domains of Pediatric Evaluation of Disability Inventory (PEDI) (Spearman’s coefficient= 0.86, p<0.0001)
  • Adequate correlation with social function domain of Pediatric Evaluation of Disability Inventory (PEDI) (Spearman’s coefficient= 0.56, p<0.0001)
  • Excellent correlation with transfer and mobility domain of Pediatric Outcomes Data Collection Instrument (PODCI) (Spearman’s coefficient= 0.88, p<0.0001)
  • Excellent correlation with upper extremity domain of Pediatric Outcomes Data Collection Instrument (PODCI) (Spearman’s coefficient= 0.80, p<0.0001)
  • Poor correlation with comfort and pain domain of Pediatric Outcomes Data Collection Instrument (PODCI) (Spearman’s coefficient= -0.13)
  • Excellent correlation with the physical function domain of Child Health Questionnaire (CHQ) (Spearman’s coefficient= 0.74, p<0.001)
  • Poor correlation with pain, general health perception, behavior and mental health domains of Child Health Questionnaire (CHQ) (Spearman’s coefficient= -0.12, 0.14, -0.30 and -0.12, respectively)

Floor/Ceiling Effects

(McCarthy et al., 2002).

GMFM Dimensions

Floor %

Ceiling %

A: Lying

0

24

B: Sitting

1

26

C: Crawling and kneeling

16

29

D: Standing

25

3

E: Walking/running/jumping

20

3

Total

0

1

Responsiveness

(Vos-Vromans, Ketelaar, & Gorter, 2005, n=55, age range= 2-7y.)

  • Standardized Response Mean (SRM)= 0.88, 1.27 (age < 48 months), 1.39 (age ≥ 48 months)
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