CPT® Code 81188

Official Description

CSTB (cystatin B) (eg, Unverricht-Lundborg disease) gene analysis; evaluation to detect abnormal (eg, expanded) alleles

Common Language Description

The CPT® Code 81188 pertains to the molecular genetic testing of the CSTB (cystatin B) gene, specifically aimed at evaluating the presence of abnormal alleles, such as expanded alleles. This testing is particularly relevant for diagnosing Unverricht-Lundborg disease, a progressive myoclonic epilepsy characterized by involuntary muscle jerking or twitching known as myoclonus. The CSTB gene is located on the long arm of chromosome 21 at position 22.3 (21q22.3) and encodes the cystatin B protein, which plays a crucial role in regulating cathepsin enzyme activity within cell lysosomes. The CSTB gene features a distinctive DNA allele with a dodecamer repeat pattern consisting of 12 amino acids, specifically CCCCG-CCCCG-CG, which typically repeats 2 to 3 times in healthy individuals. However, individuals diagnosed with Unverricht-Lundborg disease often exhibit more than 30 dodecamer repeats in both copies of the CSTB gene. In some cases, a patient may have one copy of the CSTB gene with an expanded allele while the other copy contains one of nine other identified mutations, which may include amino acid substitutions or a truncated protein that is dysfunctional. Symptoms of Unverricht-Lundborg disease generally manifest between the ages of 6 and 15 and can include myoclonus that worsens with physical exertion, stress, light, or other stimuli. As the disease progresses, patients may experience additional complications such as ataxia, tremors, dysarthria, and cognitive decline. While myoclonus is typically resistant to anti-epileptic medications, it can evolve into tonic-clonic seizures, for which treatment may be more effective. The analysis performed under CPT® Code 81188 is essential for identifying these genetic mutations, thereby aiding in the diagnosis and management of Unverricht-Lundborg disease.

1. Indications

The CSTB (cystatin B) gene analysis, represented by CPT® Code 81188, is indicated for the evaluation of individuals suspected of having Unverricht-Lundborg disease. This condition is characterized by specific symptoms and genetic markers that warrant testing. The following indications are explicitly associated with this procedure:

Unverricht-Lundborg Disease - Patients exhibiting symptoms of progressive myoclonic epilepsy, particularly myoclonus that may be exacerbated by physical exertion, stress, or light.
Family History - Individuals with a family history of Unverricht-Lundborg disease may be tested to identify potential genetic mutations that could affect their health or that of at-risk family members.

2. Procedure

The procedure for conducting the CSTB (cystatin B) gene analysis involves several critical steps to ensure accurate detection of abnormal alleles. The following procedural steps are outlined:

Step 1: Sample Collection - A biological sample, typically blood or saliva, is collected from the patient. This sample serves as the source of DNA for the genetic analysis.
Step 2: DNA Extraction - The DNA is extracted from the collected sample using standardized laboratory techniques to isolate the genetic material necessary for analysis.
Step 3: Amplification of CSTB Gene - Polymerase chain reaction (PCR) is employed to amplify the specific regions of the CSTB gene that are of interest, particularly those associated with dodecamer repeats and potential mutations.
Step 4: Analysis of Alleles - The amplified DNA is analyzed to detect the presence of expanded alleles, specifically looking for the number of dodecamer repeats in the CSTB gene. This step may involve sequencing or other molecular techniques to identify variations.
Step 5: Interpretation of Results - The results of the genetic analysis are interpreted by a qualified geneticist or laboratory professional, who will determine if the alleles are normal or if there are abnormalities indicative of Unverricht-Lundborg disease.

3. Post-Procedure

After the CSTB gene analysis is completed, patients may receive counseling regarding the results. If abnormal alleles are detected, further discussions may include the implications for the patient's health, potential treatment options, and the importance of genetic counseling for family members. Follow-up appointments may be scheduled to monitor the patient's condition and manage any symptoms associated with Unverricht-Lundborg disease. Additionally, healthcare providers may recommend further testing or evaluations based on the findings of the gene analysis.

Short Descr	CSTB GENE DETC ABNOR ALLELE
Medium Descr	CSTB GENE ANALYSIS EVAL DETECT ABNORMAL ALLELES
Long Descr	CSTB (cystatin B) (eg, Unverricht-Lundborg disease) 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

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.
GW	Service not related to the hospice patient's terminal condition