2025 CPT code 81121

IDH2 (isocitrate dehydrogenase 2 [NADP+], mitochondrial) (eg, glioma), common variants (eg, R140W, R172M).

Modifier 26 can be appended if only the professional interpretation and report are performed by a physician or other qualified healthcare professional.

Medical necessity for 81121 is established when the test is performed to assist in the diagnosis, prognosis, or treatment planning of conditions known to be associated with IDH2 variants, such as glioma. Payer-specific guidelines may apply.

The laboratory professional performs the technical aspects of the test, including cell lysis, nucleic acid extraction, amplification, and variant detection.

In simple words: This test looks for common changes in the IDH2 gene, which can be helpful in understanding the type and possible treatment of brain tumors like glioma. It's a detailed lab test that analyzes the DNA from a sample.

This molecular pathology procedure involves analyzing nucleic acid (DNA) to detect specific common variants in the IDH2 gene, which is associated with certain medical conditions such as glioma. The procedure includes all analytical steps involved in the test, from cell lysis and nucleic acid extraction to amplification and detection of variants like R140W and R172M.

Example 1: A patient with a suspected glioma undergoes a biopsy. The tissue sample is sent for molecular pathology testing, including IDH2 variant analysis (81121), to aid in diagnosis and treatment planning., A patient with a known low-grade glioma is being monitored for disease progression. IDH2 variant analysis is performed on a follow-up biopsy to evaluate any changes in the tumor's genetic profile., A patient with a newly diagnosed acute myeloid leukemia (AML) has molecular testing performed on their blood or bone marrow, including 81121, to further classify the leukemia and help guide treatment options.

Documentation should include the type of specimen submitted, the specific gene tested (IDH2), the variants analyzed, and the clinical indication for the test (e.g., suspected glioma).

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