Achieving a Diagnosis

You Can Help Identify DMD With a Creatine Kinase (CK) Test

muscle image

A CK test is a quick and often inexpensive tool1 that can potentially prevent other unnecessary testing.1 

The CK test is the first step in determining whether a neuromuscular condition is causing developmental delays and muscle weakness.2

The CK test measures the amount of CK in the blood. CK is an enzyme that is found in skeletal muscle, cardiac muscle, and the brain.3 It is released from muscle cells into the blood during muscle injury.4 Elevated levels almost always indicate skeletal muscle damage and can be observed as early as at birth.1,5

CK Levels are not checked as part of preventative pediatric care6

Although the normal range of CK levels varies with age and gender, CK levels in DMD are typically elevated 50- to 200-fold above normal levels, as shown in the table below.1

The ICD-10* diagnosis code for muscle weakness is M62.81.8

If CK is elevated, refer to a neuromuscular specialist to confirm a diagnosis.12

*International Classification of Diseases, 10th revision.

Early CK Testing is Recommended by the AAP, the AAFP, and the National Task Force for Early Identification of Childhood Neuromuscular Disorders2,5,12

American Academy of Pediatrics.
American Academy of Family Physicians.


Diagnosing DMD with Genetic Tests

If CK is elevated, the neuromuscular specialist will order genetic testing to determine whether DMD is the cause of your patient's symptoms.9 A genetic test can be used to confirm that your patient has a DMD genetic mutation and to identify the specific type of mutation.10 Types of genetic tests that can be used include, but are not limited to, the following:4 

  • Multiplex ligation-dependent probe amplification (MLPA) or array-based comparative genomic hybridization (aCGH) 
    These tests can identify large-scale mutations in the DMD gene, which are found in ~80% of patients. For the remaining ~20% of patients, additional genetic testing may be needed. 
  • Next-generation sequencing (NGS) 
    Identifies both large- and small-scale mutations in the DMD gene. Typically, no further genetic testing is required. 

In rare cases, genetic testing may be inconclusive. In these situations, the specialist may recommend a muscle biopsy to detect the presence of dystrophin.10

image of chromosome

Genetic Testing Helps Determine Treatment Eligibility

Genetic testing is crucial in DMD because certain therapies are only indicated to treat DMD caused by mutations in specific regions of the DMD gene. Some therapies may also have contraindications against specific mutations, or the location of mutations within the DMD gene.4 

Some of these mutations may also be too small to detect using MLPA or aCGH technologies.10 NGS can provide both a diagnosis, and therapeutic amenability information necessary to determine if a patient may be amenable to treatment with current or future DMD therapies.4


Sponsored Genetic Testing Programs May Be Available

Sarepta Therapeutics partners with Parent Project Muscular Dystrophy (PPMD) and Decode Duchenne, a genetic testing program that provides free genetic testing to eligible patients who have been unable to access testing due to financial barriers.

Diagnosing DMD early helps your patients and their families access appropriate management options and genetic counseling in a timely manner.11

1. Ciafaloni E, Fox DJ, Pandya S, et al. Delayed diagnosis in Duchenne muscular dystrophy: data from the Muscular Dystrophy Surveillance, Tracking, and Research Network (MD STARnet). J Pediatr. 2009;155:380-385. 2. Noritz GH, Murphy NA. Motor delays: early identification and evaluation. Pediatrics. 2013;131:e2016-e2027. 3. Baird MF, Graham SM, Baker JS, Bickerstaff GF. Creatine-kinase- and exercise-related muscle damage implications for muscle performance and recovery. J Nutr Metab. 2012;2012:960363. 4. Aartsma-Rus A, Ginjaar lB, Bushby K. The importance of genetic diagnosis for Duchenne muscular dystrophy. J Med Genet. 2016;53:145-151. 5. National Task Force for Early Identification of Childhood Neuromuscular Disorders website. Accessed on May 4, 2021. https://childmuscleweakness.org/know-the-signs/signs-of-weakness-by-age-for-primary-care 6. American Academy of Pediatrics. Recommendations for Preventive Pediatric Health Care. April 2023. Available at: https://www.aap.org/en/practice-management/bright-futures/bright-futures-materials-and-tools/bright-futures-guidelines-and-pocket-guide/ 7. Andropoulos DB. Appendix B: Pediatric normal laboratory values. In: Gregory GA, Andropoulos DB, eds. Gregory’s Pediatric Anesthesia. 5th ed. Wiley Online Library. Accessed on September 28, 2021. https://onlinelibrary.wiley.com­/doi/abs/10.1002/9781444345186.app2 8. Centers for Medicare and Medicaid Services website. Billing and coding serum phosphorus. October 5, 2021. Available at: https://www.cms.gov/medicare-coverage-database/view/article.aspx?articleId=57650 9. Birnkrant DJ, Bushby K, Bann CM, et al; for the DMD Care Considerations Working Group. Diagnosis and management of Duchenne muscular dystrophy, part 1: diagnosis, and neuromuscular, rehabilitation, endocrine, and gastrointestinal and nutritional management. Lancet Neurol. 2018;17:251-267. 10. BMJ Best Practice. Muscular Dystrophies. 2017. 11. van Ruiten HJA, Straub V, Bushby K, Guglieri M. Improving recognition of Duchenne muscular dystrophy: a retrospective case note review. Arch Dis Child. 2014;99(12):1074-1077. 12. Lurio JG, Peay HL, Mathews KD. Recognition and management of motor delay and muscle weakness in children. Am Fam Physician. 2015;91:38-44