Genetic analysis of a specific DNA region (CAG repeat length) in a blood sample
This test measures the number of repeated CAG sequences in a gene linked to certain genetic conditions. It helps assess risk for inherited disorders.
["Understanding your genetic risk for conditions like Huntington’s disease or other CAG-repeat disorders."]
Key facts at a glance
- LOINC
- 49015-1
- Short code
- SCA15 gene CAG Rpt Bld/T Ql
- Synonyms
- SCA15 gene CAG Rpt Bld/T Ql
- Category
- chemistry
- Sample
- whole-blood
- Container
- Lavender-top (EDTA)
- Units
- N/A
- Ref low
- 0.8
- Ref high
- 1.2
- Critical range
- — – 5 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- molgen
- CPT
- 85610
- SNOMED
- 396252006
- Specimen volume
- 3 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h
- Hemolysis max
- 0
- Lipemia max
- 0
- Icterus max
- 0
- TAT
- 4–24 hours
- Order
- routine
Why This Test Is Done
Your doctor may recommend this test if you have a family history of genetic disorders linked to CAG repeats, such as Huntington’s disease, spinal muscular atrophy, or certain types of myotonic dystrophy. It can also be used for carrier screening or pre-symptomatic diagnosis in at-risk individuals.
What to Expect Before the Test
You’ll provide a blood sample, typically drawn from your arm. No special preparation is needed, but inform your doctor about any medications or health conditions that could affect results.
How the Test Works
The blood sample is analyzed to count the number of CAG repeats in a specific gene. This involves genetic sequencing to detect variations in the repeat length, which can differ from the general population.
What the Results Mean
Results show the exact number of CAG repeats in your DNA. Higher or lower repeat counts may indicate an increased risk for genetic disorders, but interpretation depends on clinical context and family history.
Reference range
INR: 0.8-1.2 (warfarin: 2.0-3.0)N/A
Inform your healthcare provider if you are taking blood thinners. No special preparation required.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
This test plays a critical role in genetic counseling and risk assessment for inherited conditions. It helps guide treatment plans, family planning decisions, and monitoring for early symptoms of disorders linked to CAG repeats.
Short name
CAG Repeat Testing (Blood)
Frequently asked questions
What does a high or low CAG repeat count mean?
How long does it take to get results?
Is this test covered by insurance?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy