CPT® Code 81250

Official Description

G6PC (glucose-6-phosphatase, catalytic subunit) (eg, Glycogen storage disease, type 1a, von Gierke disease) gene analysis, common variants (eg, R83C, Q347X)

Common Language Description

Molecular genetic testing is a critical diagnostic tool used to identify specific mutations in the G6PC (glucose-6-phosphatase, catalytic subunit) gene, which is associated with glycogen storage disease, type 1a, commonly known as von Gierke disease. This gene is located on chromosome 17 and has been found to have as many as 85 different mutations. These mutations typically result in the alteration of a single amino acid within the glucose-6-phosphatase enzyme, which is situated on the membrane of the endoplasmic reticulum. The endoplasmic reticulum is an essential cellular structure involved in the transport and processing of proteins. The glucose-6-phosphatase enzyme works in conjunction with the glucose-6-phosphate translocase protein, produced from the 5LC37A4 gene, to facilitate the breakdown of glucose-6-phosphate into glucose, which is vital for energy production in cells. The glucose-6-phosphatase enzyme plays a crucial role in regulating glucose levels produced by the liver and is also active in the kidneys and intestines. When mutations occur in the G6PC gene, the function of the glucose-6-phosphatase enzyme is impaired, leading to an inability to convert glucose-6-phosphate into glucose. Instead, the process is diverted, resulting in the conversion of glucose-6-phosphate into fat and glycogen. This accumulation of fat and glycogen within cells can cause significant damage to tissues and organs, particularly affecting the kidneys and liver. Von Gierke disease is inherited in an autosomal recessive manner, meaning that individuals must inherit mutations from both parents to develop the disease. Those who inherit the mutation from only one parent are considered carriers and typically do not exhibit symptoms. Symptoms of this genetic disorder can include severe hypoglycemia, constant hunger, irritability, excessive bleeding or bruising, fatigue, abdominal distention, thin extremities, puffy cheeks, inflammatory bowel disease, stunted growth, and delayed puberty. Management of the disease involves dietary restrictions, such as limiting fructose and galactose intake, preventing low blood glucose levels through the consumption of starches like uncooked cornstarch, and administering allopurinol to lower uric acid levels. Molecular genetic testing is particularly indicated for individuals presenting with symptoms consistent with von Gierke disease or those with a family history of the condition.

1. Indications

The molecular genetic testing for the G6PC gene is indicated in the following scenarios:

Symptoms of von Gierke disease Individuals presenting with clinical manifestations associated with glycogen storage disease, type 1a, such as severe hypoglycemia, constant hunger, irritability, excessive bleeding or bruising, fatigue, abdominal distention, thin extremities, puffy cheeks, inflammatory bowel disease, stunted growth, and delayed puberty.
Family history of the disorder Individuals with a known family history of von Gierke disease may also be candidates for testing to determine if they carry the G6PC gene mutation.

2. Procedure

The procedure for molecular genetic testing of the G6PC gene involves several key steps:

Sample Collection A biological sample, typically blood or saliva, is collected from the patient. This sample contains the DNA necessary for genetic analysis.
DNA Extraction The DNA is extracted from the collected sample using laboratory techniques that isolate the genetic material from other cellular components.
Mutation Analysis The extracted DNA is then subjected to analysis to identify specific mutations within the G6PC gene. This may involve techniques such as polymerase chain reaction (PCR) and sequencing to detect common variants, including R83C and Q347X.
Data Interpretation The results of the genetic analysis are interpreted by a qualified geneticist or laboratory specialist, who will determine the presence of any mutations associated with von Gierke disease.
Reporting A comprehensive report is generated, detailing the findings of the genetic testing, including any identified mutations and their potential implications for the patient’s health.

3. Post-Procedure

After the molecular genetic testing procedure, patients may receive counseling regarding the results and their implications. If a mutation is identified, healthcare providers may discuss management strategies for von Gierke disease, including dietary modifications and monitoring for associated complications. Follow-up appointments may be scheduled to review the test results and to provide ongoing support and education regarding the condition. It is essential for patients and their families to understand the genetic aspects of the disease, including the implications for family members and potential carrier status.

Short Descr	G6PC GENE
Medium Descr	G6PC GENE ANALYSIS COMMON VARIANTS
Long Descr	G6PC (glucose-6-phosphatase, catalytic subunit) (eg, Glycogen storage disease, type 1a, von Gierke disease) gene analysis, common variants (eg, R83C, Q347X)
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)	T1H - Lab tests - other (non-Medicare fee schedule)
MUE	1
CCS Clinical Classification	234 - Pathology

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
XS	Separate structure, a service that is distinct because it was performed on a separate organ/structure
91	Repeat clinical diagnostic laboratory test: in the course of treatment of the patient, it may be necessary to repeat the same laboratory test on the same day to obtain subsequent (multiple) test results. under these circumstances, the laboratory test performed can be identified by its usual procedure number and the addition of modifier 91. note: this modifier may not be used when tests are rerun to confirm initial results; due to testing problems with specimens or equipment; or for any other reason when a normal, one-time, reportable result is all that is required. this modifier may not be used when other code(s) describe a series of test results (eg, glucose tolerance tests, evocative/suppression testing). this modifier may only be used for laboratory test(s) performed more than once on the same day on the same patient.
99	Multiple modifiers: under certain circumstances 2 or more modifiers may be necessary to completely delineate a service. in such situations modifier 99 should be added to the basic procedure, and other applicable modifiers may be listed as part of the description of the service.
GW	Service not related to the hospice patient's terminal condition