SCA Comprehensive Panel Test
SCA Comprehensive Panel Test
A condition called ataxia affects muscle movement and coordination, speech control, posture and other aspects. This is a disease that affects the nervous system due to genetic reasons, like accumulation of misfolded proteins, called ataxins, in various parts of the body. Abnormal repeats in the DNA sequences that code for different amino acids (the building block of proteins) form these misfolded proteins. When these misfolded proteins affect the neurons and the cells present in cerebellum (a part of the brain that helps in coordination and movement of muscles) and the spinal cord, it results in a type of ataxia called Spinocerebellar Ataxia (SCA). Different patterns of repeats in the DNA sequences, present in different locations in certain genes, result in different types of SCA (called subtypes), for example SCA 1, 2, 3, 6, 7, etc.
What is the SCA Comprehensive Panel Test Used For?
The SCA Comprehensive Panel Test is used to identify the particular subtype of SCA, like SCA 1, 2, 3, 6, and 7, by counting the number of repeats in the DNA sequence patterns, for example, a DNA sequence (CAG) coding for glutamine. There are other subtypes of SCA, but these are usually rarer. This test is usually advised for people with a family history of ataxia or symptoms of ataxia, getting progressively worse.
Symptoms of SCA Comprehensive Panel Test
Depending on the subtypes of the SCA, the symptoms of the ataxia caused varies. Some of the overlapping symptoms are
Worsening gait and posture
Muscle Weakness
Fatigue
Numbness
Pain in the limbs
Muscle or eye twitching
Increased reflex response of the muscles
Tremors
Psychiatric Issues
Preparation for Test
Before the test, let your general physician know of any medication, supplements or treatments that you are consuming or undergoing. If you have had bone marrow transplant, it might interfere with the test. No other special preparations are required for the test.
Interpretation of Test Results
The reference values for each of the subtypes, the abnormal values of repeats of CAG, and the abnormal values of CAG repeats with CAT interruptions are given below in the table.
Normal Values (Negative for the SCA Subtype): Reference values are normal values of the CAG repeats observed in the gene associated with the subtype. Having a result within the reference range would likely mean you do not have the particular subtype of SCA.
Abnormal Values (Positive for the SCA Subtype): Values outside of the reference range (Abnormal Values) with or without CAT interruptions may indicate that you are likely to have the respective SCA subtype.
Intermediate Values (Reduced Penetrance or Intermediate Penetrance): Certain values may be in between the reference range and the abnormal values. This may mean that you would have some chance of developing this subtype later in life, and the symptoms might be milder (reduced penetrance). This could also mean that there are chances this condition can be passed on to children (intermediate penetrance). Repeat testing may be required to confirm the results in some cases.
|
SCA Subtypes |
Normal Values (Number of CAG repeats) |
Reduced penetrance (Number of CAG repeats) |
Intermediate Penetrance (Number of CAG repeats) |
Abnormal values (Number of CAG repeats) |
|
SCA 1 |
Without CAT Interruptions: Less than 36 With CAT Interruptions: 36-43 |
38 |
Without CAT Interruptions: 36-37 |
Without CAT interruptions: More than 38 With CAT Interruptions: More than 43 |
|
SCA 2 |
Less than 32 |
33-34 |
|
More than 34 |
|
SCA 3 |
Less than 45 repeats |
|
45-59 |
More than 59 |
|
SCA 6 |
Less than 19 |
|
19 |
More than 19 |
|
SCA 7 |
Less than 19 |
34-36 |
28-33 |
More than 36 |
FAQs
How is the sample collected for the SCA Comprehensive Panel Test?
A blood sample is collected from a vein in your arm. If SCA subtype is being tested for a foetus, then the DNA of the foetus may be collected either from the mother’s blood, placenta or from cells of the foetus present in the amniotic fluid.
What is the turnaround time (TAT) for SCA Comprehensive Panel Test?
The tests results should come within 21-28 days after the sample is taken. This time would depend on the diagnostic laboratory that has taken the sample for analysis.
What should we do if we have SCA?
SCA does not have a definite cure. Depending on the subtype, the symptoms are managed by medications. More studies are being conducted to discover newer treatments for this condition.
Can SCA be inherited by the children, if one of the parents, has it?
This disease can be passed on to the children. If a copy of the defective gene for SCA is passed on to the children, then they may develop this condition.
Does this disease get worse with time?
Usually with time, the symptoms of this disease may worsen. The rate at which it progresses would depend on the subtype of this condition. For example, it has been observed that, SCA 1 progresses fast while SCA 6 has a slower progression. SCA 2 and SCA 3 have a medium progression. But the progression would vary from individual to individual.
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