Summary & Overview
CPT 81120: IDH1 Molecular Diagnostic Test
CPT code 81120 represents a laboratory technical assay to detect common sequence changes in the IDH1 gene (isocitrate dehydrogenase 1, NADP+). Molecular detection of IDH1 variants has clinical relevance across oncology and other diagnostic contexts where IDH1 mutations inform diagnosis, prognosis, or therapeutic selection. National attention to such targeted molecular testing reflects growing use of precision diagnostics in clinical workflows and payer coverage decisions.
Key payers addressed include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise overview of clinical context for IDH1 testing, typical sites of service, and which payers commonly cover laboratory molecular diagnostics. The publication also outlines expected benchmarks and policy considerations relevant to lab billing, coding accuracy, and claims adjudication when ordering or performing IDH1 molecular assays.
This summary provides clinicians, laboratory managers, and billing professionals with the clinical framing and payer landscape needed to navigate billing for CPT code 81120. It highlights what the code represents, why it matters nationally in precision medicine, and what readers will learn about coding practice, payer coverage patterns, and operational considerations. Data not available in the input will be identified where applicable in subsequent sections.
Billing Code Overview
CPT code 81120 describes a laboratory technical service that detects common alterations in the gene encoding soluble isocitrate dehydrogenase 1 (IDH1, NADP+). The procedure is a molecular diagnostic test performed by a laboratory analyst to identify presence of clinically relevant IDH1 variants.
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Service type: Laboratory molecular diagnostic testing
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Typical site of service: Clinical laboratory or hospital-based lab performing molecular pathology or genetic testing
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Clinical & Coding Specifications
Clinical Context
A 54-year-old patient with a newly diagnosed diffuse glioma undergoes tumor tissue sampling. The oncologist requests molecular testing for IDH1 mutation status to inform prognosis and therapeutic planning. A surgical pathologist submits a formalin-fixed, paraffin-embedded (FFPE) tumor specimen to the molecular diagnostics laboratory. The lab analyst performs the technical assay to detect common IDH1 gene alterations (e.g., R132H and other hotspot mutations) using immunohistochemistry, PCR-based methods, or targeted sequencing. Results are reported to the ordering pathologist and treating neuro-oncologist and integrated into the pathology report. Typical workflow steps: specimen accessioning, nucleic acid extraction or slide preparation, analytical testing for IDH1 alterations, quality control, result interpretation by the laboratory director (professional component), and release of the technical report. Typical site of service is an outpatient or hospital-based molecular diagnostics laboratory associated with pathology services.
Coding Specifications
| Modifier | Description | When to Use |
|---|---|---|
26 | Professional component | When billing only the professional/interpretive portion performed by a pathologist or molecular director |
TC |