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GMFM: Gross Motor Function Measure, Part I

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:

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GMFM: Gross Motor Function Measure, Part I

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  1. 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

  2. KB study • Looking at clinical knowledge and appropriate use of: • GMFCS • GMFM • Motor Growth Curves (MCG’s): prognosis, treatment planning

  3. Body function&structure(Impairment) Activities (Limitation) Participation (Restriction) Environmental Factors Personal Factors Interaction of Concepts ICF 2001 Health Condition (disorder/disease)

  4. 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

  5. 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)

  6. 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.

  7. GMFM Formats • GMFM-88: 88 items • GMFM-66: 66 items • GMFM-88 with reported scores for kids with Down Syndrome

  8. 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

  9. 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)

  10. GMFM-88 88 items in 5 gross motor dimensions (for ease of administration): • lying and rolling • crawling and kneeling • Sitting • Standing • walking, running and jumping

  11. GMFM-66 • Same dimensions, but 22 items eliminated (mostly in lying position)

  12. 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

  13. 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

  14. 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)

  15. 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

  16. 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

  17. 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)

  18. 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”

  19. 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

  20. Environment • Room large enough to accommodate the equipment, the child and the examiner • Private area • Consistent environment for retesting

  21. Clothing • Shorts and Tshirt are ideal • Testing is done without shoes

  22. Preparing for Testing • Have manual, equipment, score sheet ready. • Room booked, mat in place, as well as other required furniture

  23. 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

  24. 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”.

  25. 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

  26. 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

  27. 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?

  28. Knowledge Broker study CanChild research project looking at clinical knowledge and appropriate use of: • GMFCS • GMFM • Motor Growth Curves (MCG’s)

  29. 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?

  30. 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)

  31. 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.

  32. GMFM- 88 and 66 GMFM 88: 88 items in 5 gross motor dimensions: • lying and rolling • crawling and kneeling • Sitting • Standing • walking, running and jumping GMFM-66: Same dimensions, but 22 items eliminated (mostly in lying position)

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

  34. 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)

  35. 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

  36. 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)

  37. 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

  38. 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)

  39. 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)

  40. 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

  41. 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: • Research - from ASCII files or text only files (files entered into a statistical package –SPSS) • Individual GMFM-66 item scores for one or more children

  42. 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!

  43. What is the GMFM-66 score? 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.

  44. Case Summary Report • Summarizes demographic data • Summarizes score, including error (standard error and 95% confidence interval) • Graphs scores over time

  45. Item Maps • By item order or by difficulty order- by difficulty order is the most useful

  46. Appendix 3 figure A3.3 Item Map by Difficulty OrderGross Motor Function Measure GMFM-66 Client ID:3 Name:Susie Q Assessment Date:03 April 1989GMFM-66 Score:41.61 Date of Birth:07 July 1987Standard Error:1.14 Age: 1y 8m95% Confidence Interval:39.38to43.84 More Difficult Lower Motor GMFM-66 Score with 95% Confidence Intervals Higher Motor Ability Ability

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