How To Use CPT Code 81120

CPT 81120 describes the laboratory test used to detect common changes in the gene for soluble isocitrate dehydrogenase 1 (IDH1), also known as NADP+. This article will cover the description, procedure, qualifying circumstances, appropriate usage, documentation requirements, billing guidelines, historical information, similar codes and billing examples.

1. What is CPT Code 81120?

CPT 81120 is a laboratory test that detects common changes in the gene for soluble isocitrate dehydrogenase 1 (IDH1), also known as NADP+. This test is performed by a lab analyst who follows a series of technical steps to identify the presence of these changes in the gene. The test is typically ordered for individuals with glioma, a type of brain tumor, as the presence of these IDH1 mutations may have clinical implications for treatment and prognosis.

2. Official Description

The official description of CPT code 81120 is: ‘IDH1 (isocitrate dehydrogenase 1 [NADP+], soluble) (eg, glioma), common variants (eg, R132H, R132C).’ This code represents the testing for common variants in the IDH1 gene, specifically the R132H and R132C variants.

3. Procedure

1. The lab analyst performs the technical steps required for the test, starting from the extraction of nucleic acids from the specimen.
2. The lab analyst amplifies the nucleic acids to increase their quantity for analysis.
3. The lab analyst detects the target genes, specifically the common variants in the IDH1 gene, using methods such as nucleic acid probes.
4. The test is performed on specimens such as formalin-fixed paraffin-embedded tissue.

4. Qualifying circumstances

CPT 81120 is typically ordered for individuals with glioma, a type of primary brain tumor. The presence of common variants in the IDH1 gene, such as R132H and R132C, may indicate a lower-grade glioma with improved prognostic outlook. The test is performed by a lab analyst who follows specific technical steps to detect these variants in the gene.

5. When to use CPT code 81120

CPT code 81120 should be used when a clinician orders the laboratory test to detect common variants in the IDH1 gene for individuals with glioma or other relevant conditions. It is important to distinguish CPT 81120 for IDH1 common variants from CPT 81121 for IDH2 common variants.

6. Documentation requirements

To support a claim for CPT 81120, the documentation should include:

• Indication for the test, such as the presence of glioma or other relevant conditions
• Details of the technical steps performed by the lab analyst
• Specimen source, such as formalin-fixed paraffin-embedded tissue
• Results of the test, specifically the presence or absence of the common variants in the IDH1 gene

7. Billing guidelines

When billing for CPT 81120, ensure that the test is performed by a lab analyst and that the documentation supports the medical necessity of the test. It is important to distinguish CPT 81120 from CPT 81121 for IDH2 common variants. Additional codes may be reported for prep work preceding the test, such as tissue selection or microdissection, if documented. If the pathologist provides an interpretation of the test, an additional code may be reported for physician interpretation.

8. Historical information

CPT 81120 was added to the Current Procedural Terminology system on January 1, 2018. There have been no updates to the code since its addition.

9. Examples

1. A lab analyst performs CPT 81120 to detect common variants in the IDH1 gene for a patient with glioma.
2. A clinician orders CPT 81120 for a patient with a suspected genetic disorder related to the IDH1 gene.
3. A lab analyst performs CPT 81120 on formalin-fixed paraffin-embedded tissue to detect common variants in the IDH1 gene for research purposes.
4. CPT 81120 is ordered for a patient with a family history of glioma to assess their risk for the condition.
5. A lab analyst performs CPT 81120 to confirm the presence of common variants in the IDH1 gene for a patient with a suspected lower-grade glioma.
6. CPT 81120 is ordered for a patient with a known IDH1 mutation to monitor the progression of their glioma.
7. A clinician orders CPT 81120 to assess the response to treatment in a patient with glioma.
8. A lab analyst performs CPT 81120 to detect common variants in the IDH1 gene for a patient participating in a clinical trial for glioma treatment.
9. CPT 81120 is ordered for a patient with recurrent glioma to guide treatment decisions.
10. A lab analyst performs CPT 81120 to confirm the presence of common variants in the IDH1 gene for a patient with suspected glioma metastasis.