CPT® Code 81184

Official Description

CACNA1A (calcium voltage-gated channel subunit alpha1 A) (eg, spinocerebellar ataxia) gene analysis; evaluation to detect abnormal (eg, expanded) alleles

Common Language Description

The CPT® Code 81184 pertains to the molecular genetic testing of the CACNA1A gene, which encodes the calcium voltage-gated channel subunit alpha1 A. This gene is critically involved in the functioning of calcium channels that facilitate the transport of calcium ions across cell membranes, playing a vital role in neuronal communication and neurotransmitter release. The CACNA1A gene is located on the short arm of chromosome 19 at position 13.13 (19p13.13). The analysis performed under this code specifically aims to evaluate and detect abnormal alleles, particularly those associated with spinocerebellar ataxia type 6 (SCA6), a hereditary condition characterized by progressive degeneration of the cerebellum and spinal cord. In SCA6, a specific region of the CACNA1A gene exhibits a trinucleotide repeat pattern of CAG (cytosine-adenine-guanine), which typically repeats between 4 to 18 times in unaffected individuals. However, in affected individuals, this repeat can expand to between 20 to 33 times, correlating with the onset and severity of symptoms. Symptoms of SCA6 may include ataxia, dystonia, tremors, dysarthria, nystagmus, and diplopia, with the number of CAG repeats influencing the age of onset. The testing provided by code 81184 is essential for identifying these expanded alleles, thereby aiding in the diagnosis and understanding of the genetic basis of this condition.

1. Indications

The molecular genetic testing represented by CPT® Code 81184 is indicated for the evaluation of individuals suspected of having spinocerebellar ataxia type 6 (SCA6). This condition is characterized by a range of symptoms that may include:

Uncoordinated gait (ataxia) - Difficulty in maintaining balance and coordination while walking.
Dystonia - Involuntary muscle contractions leading to abnormal postures or movements.
Tremors - Involuntary shaking movements, often affecting the hands or limbs.
Loss of arm coordination - Difficulty in performing tasks that require fine motor skills.
Difficulty with speech (dysarthria) - Slurred or slow speech due to muscle control issues.
Involuntary movement of eye muscles (nystagmus) - Rapid, uncontrolled eye movements.
Double vision - Visual disturbance where two images of a single object are seen.

2. Procedure

The procedure for CPT® Code 81184 involves several key steps to ensure accurate evaluation and detection of abnormal alleles in the CACNA1A gene:

Sample Collection - A biological sample, typically blood or saliva, is collected from the patient to obtain DNA for analysis.
DNA Extraction - The DNA is extracted from the collected sample using standard laboratory techniques to isolate the genetic material for testing.
Amplification of Target Region - Polymerase chain reaction (PCR) is employed to amplify the specific region of the CACNA1A gene that contains the trinucleotide repeat sequence, allowing for sufficient material to analyze.
Analysis of Trinucleotide Repeats - The amplified DNA is analyzed to determine the number of CAG repeats present in the CACNA1A gene. This step is crucial for identifying whether the allele is normal or expanded.
Interpretation of Results - The results are interpreted by a qualified geneticist or laboratory professional, who assesses the number of repeats and determines if they fall within the normal range or indicate a mutation associated with SCA6.

3. Post-Procedure

After the completion of the genetic testing under CPT® Code 81184, patients may receive counseling regarding the results. If abnormal alleles are detected, further discussions may include the implications for the patient’s health, potential symptoms, and the risk of transmission to family members. Genetic counseling is recommended to help patients and their families understand the results and consider options for management or further testing, if necessary. Follow-up appointments may be scheduled to discuss the findings in detail and to provide support for any emotional or psychological impacts resulting from the diagnosis.

Short Descr	CACNA1A GEN DETC ABNOR ALLEL
Medium Descr	CACNA1A GENE ANALYSIS EVAL DETECT ABNOR ALLELES
Long Descr	CACNA1A (calcium voltage-gated channel subunit alpha1 A) (eg, spinocerebellar ataxia) gene analysis; evaluation to detect abnormal (eg, expanded) alleles
Status Code	Statutory Exclusion (from MPFS, may be paid under other methodologies)
Global Days	XXX - Global Concept Does Not Apply
PC/TC Indicator (26, TC)	9 - Not Applicable
Multiple Procedures (51)	9 - Concept does not apply.
Bilateral Surgery (50)	9 - Concept does not apply.
Physician Supervisions	09 - Concept does not apply.
Assistant Surgeon (80, 82)	9 - Concept does not apply.
Co-Surgeons (62)	9 - Concept does not apply.
Team Surgery (66)	9 - Concept does not apply.
Diagnostic Imaging Family	99 - Concept Does Not Apply
CLIA Waived (QW)	No
APC Status Indicator	Service Paid under Fee Schedule or Payment System other than OPPS
Type of Service (TOS)	5 - Diagnostic Laboratory
Berenson-Eggers TOS (BETOS)	none
MUE	1

GA	Waiver of liability statement issued as required by payer policy, individual case
59	Distinct procedural service: under certain circumstances, it may be necessary to indicate that a procedure or service was distinct or independent from other non-e/m services performed on the same day. modifier 59 is used to identify procedures/services, other than e/m services, that are not normally reported together, but are appropriate under the circumstances. documentation must support a different session, different procedure or surgery, different site or organ system, separate incision/excision, separate lesion, or separate injury (or area of injury in extensive injuries) not ordinarily encountered or performed on the same day by the same individual. however, when another already established modifier is appropriate it should be used rather than modifier 59. only if no more descriptive modifier is available, and the use of modifier 59 best explains the circumstances, should modifier 59 be used. note: modifier 59 should not be appended to an e/m service. to report a separate and distinct e/m service with a non-e/m service performed on the same date, see modifier 25.
90	Reference (outside) laboratory: when laboratory procedures are performed by a party other than the treating or reporting physician or other qualified health care professional, the procedure may be identified by adding modifier 90 to the usual procedure number.