Bye E1,2, Glinsky J1, Yeomans J3, Hungerford A4, Patterson H2, Chen L1,3, Harvey L1
1John Walsh Centre for Rehabilitation Research, Sydney Medical School/Northern, University of Sydney, Sydney, Australia, 2Spinal Injury Unit, Prince of Wales Hospital, Sydney, Australia, 3Spinal Injury Unit, Royal North Shore Hospital, Sydney, Australia, 4Spinal Injury Unit, Royal Rehab, Sydney, Australia
Background: Muscle weakness impacts the function and independence of people with spinal cord injury (SCI). Clinical trials are increasingly being conducted to determine the most effective ways to strengthen these neurologically weak muscles. Trials often target one muscle group in order to answer initial mechanistic questions. The commonly used primary outcome measure in these trials is strength measured with dynamometers. However, dynamometers are expensive, not readily available in clinical practice and not feasible for large multi-centred clinical trials. Therefore, manual muscle testing may be the most pragmatic option. However, the 6-point scale has a very restricted range, which limits its usefulness in statistical analyses. The 13-point MMT is a modification of the original 6-point scale with pluses and minuses. This scale fell out of favour in the 1990s due to concerns about its reliability but we could not identify studies, which had formally tested the reliability of the 13-point MMT. We reasoned that provided the reliability was adequate then the 13-point MMT may be a reasonable option for trials involving one muscle, particularly if the sample size is sufficient to overcome any noise in the data due to restricted reliability. Therefore, we felt it was timely to revisit the 13-point MMT for use in clinical trials and to determine its potential usefulness.
Purpose: The purpose of this study was to determine the inter-rater reliability of the 13-point manual muscle test (MMT).
Methods: We determined the inter-rater reliability of the 13-point MMT for the biceps and/or wrist extensors of individuals with tetraplegia. Sixty inpatients and outpatients were recruited from three SCI units in NSW, Australia. Muscle strength of the wrist extensors and/or elbow flexors were assessed by 2 experienced physiotherapists on the same day. The order of the assessments by the two different physiotherapists was randomized. The assessors were blinded to the results of each other's assessments.
Results: The ICC (95% confidence interval) reflecting the agreement of the two assessors results across all grades was 0.98 (0.97 to 0.99). The two assessors were within one, two and three points (out of 13 points) of each other, 85%, 93% and 99% of the time, respectively. The ICC (95% confidence interval) for grades 3 or lower was 0.94 (0.90 to 0.97) and for above 3 was 0.70 (0.51 to 0.82).
Conclusion(s): The 13-point MMT scale is sufficiently reliable for use in clinical trials involving weak muscles where dynamometers are not appropriate.
Implications: The manual muscle test can be used in clinical trials where strength of one muscle group is the primary outcome measure. Its main advantage over other options is that it is quick and easy to administer and requires minimal equipment and training, considerations important for multi-centred trials.
Keywords: Manual muscle test, reliability, spinal cord injury
Funding acknowledgements: iCARE
Purpose: The purpose of this study was to determine the inter-rater reliability of the 13-point manual muscle test (MMT).
Methods: We determined the inter-rater reliability of the 13-point MMT for the biceps and/or wrist extensors of individuals with tetraplegia. Sixty inpatients and outpatients were recruited from three SCI units in NSW, Australia. Muscle strength of the wrist extensors and/or elbow flexors were assessed by 2 experienced physiotherapists on the same day. The order of the assessments by the two different physiotherapists was randomized. The assessors were blinded to the results of each other's assessments.
Results: The ICC (95% confidence interval) reflecting the agreement of the two assessors results across all grades was 0.98 (0.97 to 0.99). The two assessors were within one, two and three points (out of 13 points) of each other, 85%, 93% and 99% of the time, respectively. The ICC (95% confidence interval) for grades 3 or lower was 0.94 (0.90 to 0.97) and for above 3 was 0.70 (0.51 to 0.82).
Conclusion(s): The 13-point MMT scale is sufficiently reliable for use in clinical trials involving weak muscles where dynamometers are not appropriate.
Implications: The manual muscle test can be used in clinical trials where strength of one muscle group is the primary outcome measure. Its main advantage over other options is that it is quick and easy to administer and requires minimal equipment and training, considerations important for multi-centred trials.
Keywords: Manual muscle test, reliability, spinal cord injury
Funding acknowledgements: iCARE
Topic: Neurology: spinal cord injury
Ethics approval required: Yes
Institution: Royal North Shore Hospital
Ethics committee: Northern Sydney Local Health District
Ethics number: LNR/17/HAWKE/240
All authors, affiliations and abstracts have been published as submitted.
