Summary & Overview
CPT 81243: FMR1 (Fragile X) Gene Test, Technical Component
CPT code 81243 represents a molecular laboratory test that detects changes in the fragile X messenger ribonucleoprotein 1 gene (FMR1), most commonly identifying expanded CGG repeat sequences linked to fragile X-associated conditions. This code captures the technical laboratory component of FMR1 analysis used in diagnostic evaluation, reproductive counseling, and assessment of neurodevelopmental disorders. Nationally, FMR1 testing matters because it informs clinical diagnosis, family planning, and eligibility for targeted services and supports.
Key payers covered in the analysis include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise clinical context for when FMR1 testing is performed, the typical laboratory setting for the service, and what the CPT code denotes. The publication outlines expected use cases for the code, common modifiers provided in the input, and notes on payer coverage patterns where available. It also summarizes relevant benchmarking and policy considerations for a national audience, and highlights areas where input data was not provided.
Billing Code Overview
CPT code 81243 describes a laboratory technical test to detect changes in the fragile X messenger ribonucleoprotein 1 gene (FMR1). The service typically identifies common abnormal forms involving expanded CGG repeat sequences in the FMR1 gene that are associated with fragile X spectrum conditions.
Service type: Molecular genetic diagnostic test (laboratory technical component)
Typical site of service: Clinical laboratory or hospital laboratory
Data not available in the input.
Clinical & Coding Specifications
Clinical Context
A typical patient is a pediatric or adult with developmental delay, intellectual disability, autism spectrum disorder, or a family history of fragile X syndrome referred for genetic testing. The clinician (pediatrician, geneticist, or neurologist) orders molecular testing to assess the FMR1 gene for CGG trinucleotide repeat expansions or methylation abnormalities. A blood sample is collected in clinic or at an outpatient phlebotomy site and sent to the molecular diagnostic laboratory. The laboratory performs the technical assay described by 81243 (FMR1 analysis) and generates a report indicating repeat size categories (normal, intermediate/gray zone, premutation, full mutation) and, when applicable, methylation status which informs diagnosis, carrier status, and reproductive counseling. Results are transmitted to the ordering clinician, who integrates findings into the patient’s care plan and documents the medical necessity for the test in the chart.
Coding Specifications
| Modifier | Description | When to Use |
|---|---|---|
26 | Professional component | Use when reporting only the interpretive component if the laboratory separates technical and professional components and the physician provides interpretation. |
TC |