CPT® Code 81189

Official Description

CSTB (cystatin B) (eg, Unverricht-Lundborg disease) gene analysis; full gene sequence

Common Language Description

The CPT® Code 81189 pertains to the molecular genetic testing of the CSTB (cystatin B) gene, specifically focusing on a full gene sequence analysis. This testing is crucial for identifying mutations associated with Unverricht-Lundborg disease, a progressive myoclonic epilepsy that typically manifests between the ages of 6 and 15. The CSTB gene, located on chromosome 21 at position 21q22.3, encodes the cystatin B protein, which plays a significant role in regulating cathepsin enzyme activity within cell lysosomes. The gene features a distinctive DNA allele characterized by a dodecamer repeat pattern of 12 amino acids, which usually occurs 2-3 times in healthy individuals. However, individuals diagnosed with Unverricht-Lundborg disease often exhibit more than 30 repeats in both copies of the CSTB gene. In some cases, one copy may have an expanded allele while the other may present with one of nine identified mutations, such as amino acid substitutions or truncated proteins that are dysfunctional. The clinical presentation of this condition includes involuntary muscle jerking (myoclonus), which can be aggravated by various stimuli, and may progress to more severe symptoms like ataxia, dysarthria, and cognitive decline. The full gene sequence analysis provided by CPT® Code 81189 allows for a comprehensive examination of the CSTB gene, facilitating the identification of functional variants and genetic markers that may contribute to the disease's pathology.

1. Indications

The molecular genetic testing for the CSTB (cystatin B) gene analysis is indicated for the following conditions:

Unverricht-Lundborg disease - A progressive myoclonic epilepsy characterized by symptoms such as involuntary muscle jerking (myoclonus), ataxia, dysarthria, and cognitive decline, typically beginning between the ages of 6 and 15.

2. Procedure

The procedure for conducting a full gene sequence analysis of the CSTB gene involves several detailed steps:

Step 1: Sample Collection - A biological sample, usually blood or saliva, is collected from the patient to obtain DNA for analysis. This sample serves as the source material for the genetic testing.
Step 2: DNA Extraction - The DNA is extracted from the collected sample using standard laboratory techniques to isolate the genetic material necessary for analysis.
Step 3: Full Gene Sequencing - The extracted DNA undergoes full gene sequencing of the CSTB gene. This process involves amplifying the gene segments and sequencing them to identify the exact order of nucleotides.
Step 4: Data Analysis - The sequenced data is analyzed to identify any mutations or variations in the CSTB gene. This includes comparing the gene segments to reference sequences to pinpoint functional variants, introns, exons, and regulatory elements.
Step 5: Identification of Genetic Markers - Genetic markers are identified by detecting point mutations or single nucleotide polymorphisms (SNPs) that may be associated with Unverricht-Lundborg disease.
Step 6: Reporting Results - The findings from the analysis are compiled into a report that details any identified mutations or variants, which can be used for further clinical decision-making and family counseling.

3. Post-Procedure

After the completion of the CSTB gene analysis, the patient may receive genetic counseling to discuss the results and their implications. If mutations are identified, family members may also be advised to undergo testing to determine their risk of developing Unverricht-Lundborg disease. The results can guide management strategies for the patient, including monitoring for symptoms and potential interventions. It is important to note that the interpretation of genetic test results should be conducted by qualified healthcare professionals to ensure accurate understanding and appropriate follow-up care.

Short Descr	CSTB GENE FULL GENE SEQUENCE
Medium Descr	CSTB GENE ANALYSIS FULL GENE SEQUENCE
Long Descr	CSTB (cystatin B) (eg, Unverricht-Lundborg disease) gene analysis; full gene sequence
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

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.
XU	Unusual non-overlapping service, the use of a service that is distinct because it does not overlap usual components of the main service
GW	Service not related to the hospice patient's terminal condition
XS	Separate structure, a service that is distinct because it was performed on a separate organ/structure