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North Star Ambulatory Assessment

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Purpose

The North Star Ambulatory Assessment (NSAA) is a 17-item rating scale that is used to evaluate motor performance in ambulant boys with Duchenne Muscular Dystrophy (DMD). It is used to assess functional abilities, monitor disease progression, and evaluate the effectiveness of therapies and interventions over time. 

Link to Instrument

Link to Instrument

Acronym NSAA

Area of Assessment

Bodily Functions

Administration Mode

Paper & Pencil

Cost

Free

CDE Status

Classified as Supplemental for Outcomes and Endpoints/Functional Status: Duchenne Muscular Dystrophy/Becker Muscular Dystrophy (DMD/BMD) and Spinal Muscular Atrophy (SMA) (Last searched 8/11/2025) 

Populations

Neuromuscular Conditions

Key Descriptions

  • The North Star Ambulatory Assessment (NSAA) is only given to participants who are ambulant.
  • The NSAA is used to evaluate functional motor performance in boys with Duchenne Muscular Dystrophy.
  • Participants must complete 17 tasks.
  • Items are scored based on the following grading scale:
    0: Unable to achieve independently
    1: Modified method but achieves goal independent of physical assistance from another
    2: ‘Normal’ - no obvious modification of activity
  • Minimum score: 0; maximum score: 34
  • Test administrator provides standardized verbal instructions for each motor task to be performed by the participant.
  • Further instructions and scoring details can be found in the manual for the NSAA.

Number of Items

17

Equipment Required

  • Box Step (approximately 15cm tall)
  • Size appropriate chair OR height adjustable plinth
  • Floor Mat
  • Straight 10m walkway
  • Stopwatch

Time to Administer

10 minutes

Required Training

Reading an Article/Manual

Required Training Description

Training for administration and interpretation of the NSAA is recommended but not required.

Recommended training involves reviewing the official assessment manual, which provides a comprehensive overview of the test, including test description, test guidelines, set-up procedures, and detailed instructions for each individual item. For each item, the manual outlines the starting position, standardized verbal instructions provided by the administrator, item—specific scoring criteria, written descriptions of performance corresponding to each rating score, and photographic examples for reference.

Audio-guided training and video demonstrations of therapists administering the NSAA are available to use in conjunction with the manual.

There are no specific degree requirements associated with the administration of the NSAA however, it is typically administered by trained healthcare professionals with relevant clinical experience.

Manual: https://www.pod-nmd.org/wp-content/uploads/2023/11/NSAA-_Manual_-15102020-Copy.pdf
Audio-guided Training: https://pod-treatnmd.talentlms.com/
Video Demonstrations: https://pod-treatnmd.talentlms.com/

Age Ranges

Preschool Children

3 - 5

years

Child

6 - 12

years

Adolescent

13 - 17

years

Adult

18 - 64

years

Instrument Reviewers

Reviewed in August 2025 by University of Washington Master of Occupational Therapy students Emily Boeschoten, Emily Hancock, Maria Madero, and McKenna Ross under the direction of faculty mentor Brittany St. John, PhD, MPH, OTR/L, Division of Occupational Therapy, Department of Rehabilitation Medicine, University of Washington, Seattle

Body Structure

Head
Neck
Lower Extremity

ICF Domain

Body Function
Activity

Measurement Domain

Motor

Professional Association Recommendation

  • North Star Clinical Network for Pediatric Neuromuscular Disease: The NSAA was developed by the physiotherapy assessment and evaluation group of this network. 
  • Muscular Dystrophy UK: Continue to support the development and use of the NSAA within the North Star Network.

 

Considerations

Available Translations:

  • Spanish
  • Portuguese
  • Greek
  • Italian
  • French
  • Turkish
  • Chinese

 

Neuromuscular Conditions

back to Populations

Minimal Detectable Change (MDC)

Duchenne Muscular Dystrophy: (Muntoni et al., 2024; n = 1012, mean age at 1st visit = 8.1 (2.3) years, age range = ≥ 4 to <18, minimum NSAA score > 12, median follow-up = 24.7 months)

  • MDC threshold for 80% confidence of true change in NSAA score = 2.8 score units (4.2 score units for 90% confidence)

 

Minimally Clinically Important Difference (MCID)

Duchenne Muscular Dystrophy: (Muntoni et al., 2024; n = 156 (306 48-week intervals), anchor-based MCID)

  • Average change of 2.2 units in the NSAA total score was associated with a 1-unit worsening in the Functional Motor Score

 

Duchenne Muscular Dystrophy: (Gupta et al, 2023; n = 663; mean age = 7.8 (1.1) years, age range = 6.5-10.5)

  • MCID in boys 7-10 years based on distribution-based approach (⅓ SD) = 2.3-2.9 points on raw scale and 5.6-6.8 on linearized scale; based on SEM approach, MCID = 2.9-3.5 points on raw scale and 6.5-8.2 on linearized scale; based on anchor-based approach (6MWD)= 3.5 points on raw scale above age of 7 years
  • 5.6 (on linearized scale) (n = 338)
    • 7 years old
    • Method: ⅓ SD
  • 6.5 (on linearized scale) (n = 338)
    • 7 years old
    • Method: SEM
  • 6.0 (on linearized scale) (n = 350)
    • 8 years old
    • Method: ⅓ SD
  • 7.2 (on linearized scale) (n = 350)
    • 8 years old
    • Method: SEM
  • 6.7 (on linearized scale) (n = 306)
    • 9 years old
    • Method: ⅓ SD
  • 8.1 (on linearized scale) (n = 306) 
    • 9 years old
    • Method: SEM
  • 6.8 (on linearized scale) (n = 249)
    • 10 years old
    • Method: ⅓ SD
  • 8.2 (on linearized scale) (n = 249)
    • 10 years old
    • Method: SEM

 

Duchenne Muscular Dystrophy: (Mayhew et al., 2013; n = 198; mean age = 8.5 (2.5) years, age range = 3-12 years)

  • Daily prednisolone regime
    • MCID: 8.8 (0.5) score units
  • Intermittent prednisolone regime
    • MCID: 6.9 (0.5) score units

 

Test/Retest Reliability

Duchenne Muscular Dystrophy: (Mazzone et al., 2009; age range = 5 years – 9 years, 11 months; video-based administration)

  • Acceptable to Excellent test-retest reliability (Spearman- Brown Coefficient = 0.70-1)

 

Interrater/Intrarater Reliability

Duchenne Muscular Dystrophy: (Emery et al., 2022; n = 10; mean age = 8.17 years, age range = 44.9m – 17y, 3m; video-based administration; physiotherapist raters)

  • Excellent interrater reliability (ICC = 0.98)

 

Duchenne Muscular Dystrophy: (Mazzone et al., 2009; age range = 5 years – 9 years, 11 months; video-based administration; physiotherapist rater who organized training session was involved in the development of the NSAA and in the UK training program for NSAA; all therapists administering the NSAA had experience with neuromuscular disorders and with functional scales in DMD)

  • Excellent interrater reliability (ICC = 0.995)
  • Excellent intrarater reliability (ICC = 0.95)

 

Duchenne Muscular Dystrophy: (Okama et al., 2017; n = 35; mean age = 9 (2.83) years, age range = 4-15 years; Portuguese translation of NSAA))

  • Excellent interrater reliability (ICC = 0.962)
  • Excellent intrarater reliability (ICC = 0.988)

 

Internal Consistency

Duchenne Muscular Dystrophy: (Mayhew et al., 2011; n = 191; mean age = 7.67 (2.34) years, age range = 3.5-15.42 years)

  • Excellent: Pearson Separation Index = 0.91

 

Duchenne Muscular Dystrophy: (Okama et al., 2017)

  • Excellent: Cronbach’s alpha = 0.935

 

Construct Validity

Convergent validity:

 

Duchenne Muscular Dystrophy: (Okama et al., 2017; n = 31)

  • Excellent convergent validity of the NSAA total score with the Motor Function Measure (MFM) total score (r = 0.863, p < 0.01)
  • Adequate to Excellent convergent validity of individual items of the NSAA with the MFM total score (r = 0.494 to 0.842), except items 10 (“Gets to sitting”, p = 0.326) and 12 (“Lifts head”, p = 0.125), whose correlations with the MFM total score were not significant. 
  • Adequate correlation of the NSAA with the 6-minute walk test (r = 0.433; p = 0.027).

 

Content Validity

Duchenne Muscular Dystrophy: (Mayhew et al., 2011)

  • Content validity of the NSAA was determined by comparing the ranking of test item difficulty by 5 expert physiotherapists to the study’s Rasch analysis output. The study found the two ranking outputs to be similar (p = 0.80) showing satisfactory content validity.

     

Duchenne Muscular Dystrophy:(Okama et al., 2017)

  • Content validity of the NSAA was determined to be satisfactory by an expert committee review.

 

Face Validity

Duchenne Muscular Dystrophy:(Okama et al., 2017)

  • Face validity of the NSAA was determined to be satisfactory by an expert committee review.

 

Floor/Ceiling Effects

Duchenne Muscular Dystrophy: (Mayhew et al., 2011)

  • Adequate: Minimal ceiling and floor effects found (no percentage values specified)

 

Duchenne Muscular Dystrophy: (Okama et al., 2017)

  • Adequate ceiling effect of 5.7% found for the NSAA total score
  • Poor to Adequate ceiling effects of 8.6 to 65.7% for individual items of NSAA
  • Excellent: no floor effects for total score or individual items 1 (stand) and 2 (walk) 
  • Poor to Adequate floor effects of 2.8 to 42.8% for individual items 3 through 17

 

Responsiveness

Duchenne Muscular Dystrophy: (Mayhew et al., 2013)

  • Daily prednisolone regime by age group
    • 3/4-5 Years: not statistically significant (p = 0.12; Moderate Change: effect size = 0.57)
    • 5-6 Years: statistically significant (p = 0.00; Moderate Change: effect size = 0.63)
    • 6-7 Years: not statistically significant (p = 0.28; Small Change: effect size = -0.15)
    • 7-8 Years: not statistically significant (p = 0.08; Moderate Change: effect size = -0.25)
    • 8-9 Years: statistically significant (p = 0.05; Moderate Change: effect size = -0.48)
    • 9-10 Years: not statistically significant (p = 0.09; Moderate Change: effect size = -0.23)
    • 10-11 Years: statistically significant (p = 0.01; Moderate Change: effect size = -0.48)
    • 11-12 Years: statistically significant (p = 0.02; Moderate Change: effect size = -0.67)

 

  • Intermittent prednisolone regime by age group
    • 3/4-5 Years: statistically significant (p = 0.00; Large Change: effect size = 0.90)
    • 5-6 Years: not statistically significant (p = 0.08; Moderate Change: effect size = 0.39)
    • 6-7 Years: not statistically significant (p = 0.87; Small Change: effect size = -0.02)
    • 7-8 Years: not statistically significant (p = 0.11; Moderate Change: effect size = -0.45)
    • 8-9 Years: statistically significant (p = 0.01; Moderate Change: effect size = -0.53)
    • 9-10 Years: statistically significant (p = 0.00; Large Change: effect size = -0.95)
    • 10-11 Years: statistically significant (p = 0.00; Large Change: effect size = -1.01)
    • 11-12 Years: not statistically significant (p = 0.27; Moderate Change: effect size = -0.52)

 

Bibliography

Ayyar Gupta, V., Pitchforth, J. M., Domingos, J., Ridout, D., Iodice, M., Rye, C., Chesshyre, M., Wolfe, A., Selby, V., Mayhew, A., Mazzone, E. S., Ricotti, V., Hogrel, J. Y., Niks, E. H., de Groot, I., Servais, L., Straub, V., Mercuri, E., Manzur, A. Y., Muntoni, F., … iMDEX Consortium and the U.K. NorthStar Clinical Network (2023). Determining minimal clinically important differences in the North Star Ambulatory Assessment (NSAA) for patients with Duchenne muscular dystrophy. PloS one, 18(4), e0283669. https://doi.org/10.1371/journal.pone.0283669

Emery, N., Strachan, K., Kulshrestha, R., Kuiper, J. H., & Willis, T. (2022). Evaluating the Feasibility and Reliability of Remotely Delivering and Scoring the North Star Ambulatory Assessment in Ambulant Patients with Duchenne Muscular Dystrophy. Children (Basel, Switzerland), 9(5), 728. https://doi.org/10.3390/children9050728

Great Ormond Street Hospital NHS Foundation Trust & The Newcastle upon Tyne Hospitals NHS Foundation Trust. (2020, September 30). North Star Ambulatory Assessment (NSAA). https://www.pod-nmd.org/wp-content/uploads/2023/11/NSAA-_Manual_-15102020-Copy.pdf; https://pod-treatnmd.talentlms.com/; https://pod-treatnmd.talentlms.com/ 

Mayhew, A. G., Cano, S. J., Scott, E., Eagle, M., Bushby, K., Manzur, A., & Muntoni, F. (2013). Detecting meaningful change using the north star ambulatory assessment in duchenne muscular dystrophy. Developmental Medicine and Child Neurology., 55(11), 1046–1052. https://doi.org/10.1111/dmcn.12220

Mayhew, A.G., Cano, S., Scott, E., Eagle, M., Bushby, K., & Muntoni, F. (2011). Moving towards meaningful measurement: Rasch analysis of the north star ambulatory assessment in duchenne muscular dystrophy. Developmental Medicine and Child Neurology., 53(6), 535–542. https://doi.org/10.1111/j.1469-8749.2011.03939.x

Mazzone, E.S., Messina, S.,Vasco, G., Main, M., Eagle, M., D’Amico, A., Doglio, L., Politano, L., Cavallaro, F., Frosini, S., Bello, L., Magri, F., Corlatti, A., Zucchini, E., Brancalion, B., Rossi, F., Ferretti, M., Motta, M.G., Cecio, M.R.,... Mercuri, E. (2009) Reliability of the north star ambulatory assessment in a multicentric setting. Neuromuscular Disorders, 19(7) 458-461. https://doi.org/10.1016/j.nmd.2009.06.368

Muntoni, F., Signorovitch, J., Sajeev, G., Done, N., Yao, Z., Goemans, N., McDonald, C., Mercuri, E., Niks, E. H., Wong, B., Vandenborne, K., Straub, V., de Groot, I. J. M., Tian, C., Manzur, A., Dieye, I., Lane, H., Ward, S. J., Servais, L., PRO-DMD-01 study investigators, … cTAP (2024). Meaningful changes in motor function in Duchenne muscular dystrophy (DMD): A multi-center study. PloS one, 19(7), e0304984. https://doi.org/10.1371/journal.pone.0304984 

North Star Clinical Network. North Star Ambulatory Assessment (NSAA). https://www.touchneurology.com/wp-content/uploads/sites/3/2018/03/www.musculardystrophyuk.org_assets_0000_6388_NorthStar.pdf. 

Okama, L. O., Zampieri, L. M., Ramos, C. L., Toledo, F. O., Alves, C. R. J., Mattiello-Sverzut, A. C., Mayhew, A., & Sobreira, C. F. R. (2017). Reliability and validity analyses of the North Star Ambulatory Assessment in Brazilian Portuguese. Neuromuscular disorders : NMD, 27(8), 723–729. https://doi.org/10.1016/j.nmd.2017.05.013

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