Summary & Overview

CPT 86364: Tissue Transglutaminase Antibody (TTG) Serology

CPT code 86364 represents a laboratory serologic test for tissue transglutaminase (TTG) antibodies, such as TTG IgG or TTG IgA, commonly performed by immunoassay methods like ELISA. This test is clinically important because detection of TTG antibodies supports the diagnosis of celiac disease and can assist in monitoring response to a gluten-free diet. Nationally, TTG antibody testing is a widely used first-line serologic screen in patients with suspected celiac disease and in follow-up care.

Key payers covered in this analysis include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise overview of what CPT code 86364 represents, the clinical context for its use, and typical service settings. The publication outlines common modifiers associated with laboratory services and provides benchmarks and policy-relevant updates where available. The content also summarizes clinical indications and how results are used in diagnostic pathways and patient monitoring. Data not available in the input is clearly noted where applicable.

AetnaBlue Cross Blue ShieldCigna HealthUnitedHealthcareMedicare86364CPTserologytissue transglutaminaseceliac diseaseimmunoassayELISAlaboratorydiagnostic testing

Billing Code Overview

CPT code 86364 describes a laboratory test that detects tissue transglutaminase (TTG) antibodies in a specimen such as serum, for example TTG IgG or TTG IgA. Common methods for performing this assay include immunoassays such as enzyme–linked immunosorbent assay (ELISA). The presence of TTG antibodies supports the diagnosis of celiac disease, an autoimmune disorder that causes inflammation of the small intestine in response to dietary gluten. Test results may also help clinicians monitor patient adherence to treatment.

Service type: Laboratory serologic immunoassay for TTG antibodies

Typical site of service: Clinical laboratory or hospital laboratory; outpatient specimen collection sites

Clinical & Coding Specifications

Clinical Context

A 32-year-old female presents to her primary care clinic with a 6-month history of intermittent diarrhea, abdominal pain, bloating, and iron-deficiency anemia. The clinician suspects celiac disease based on symptoms and family history of autoimmune disorders. A serum test for tissue transglutaminase antibodies is ordered to evaluate for gluten-sensitive enteropathy prior to any dietary change. The specimen is collected in the outpatient phlebotomy area and sent to the clinical laboratory where an immunoassay (commonly ELISA) is performed to detect TTG IgA and, if indicated by IgA deficiency, TTG IgG. Results are reported to the ordering clinician and used alongside serology, HLA typing, and/or duodenal biopsy findings to establish diagnosis and to monitor adherence to a gluten-free diet in follow-up visits.

Coding Specifications

Modifier	Description	When to Use
`26`	Professional component	Use when only the professional interpretation or reading of the laboratory result is billed separately from the technical component.
`TC`	Technical component	Use when billing only the laboratory technical component (performing the assay) without professional interpretation.
`59`	Distinct procedural service	Use when this laboratory test is distinct from other services on the same day that might otherwise be bundled.
`90`	Reference (outside) laboratory	Use when the specimen is sent to an outside/reference laboratory for testing.
`91`	Repeat clinical diagnostic laboratory test	Use when the test is repeated on the same day to obtain a valid result.
`52`	Reduced services	Use when the test is partially reduced or not fully performed as described by the code.
`53`	Discontinued procedure	Use when specimen collection or testing is started but discontinued due to patient factors or specimen issues.
`23`	Unusual anesthesia	Rarely applicable but used when unusual anesthesia is necessary for specimen collection in special circumstances.
`25`	Significant, separately identifiable E/M service	Use when an evaluation and management service on the same day is significant and separately reportable from ordering the lab.
`59`	Distinct procedural service	Use when necessary to show the TTG test is distinct from other same-day procedures (listed again for emphasis when applicable).

Taxonomy Code	Specialty	Notes
`207Q00000X`	Gastroenterology	Gastroenterologists commonly order `86364` when evaluating suspected celiac disease.
`208D00000X`	Family Medicine	Primary care physicians frequently order serologic testing as initial evaluation.
`207L00000X`	Allergy & Immunology	Allergists/immunologists may order TTG testing when evaluating autoimmune or IgA deficiency contexts.
`261Q00000X`	Clinical Pathology	Pathology/laboratory medicine specialists oversee assay validation and reporting.
`207K00000X`	Internal Medicine	Internists manage chronic GI symptoms and coordinate serologic testing.

Related Diagnoses

ICD-10 Code	Description	Clinical Relevance
`K90.0`	Celiac disease	Primary diagnosis for which `86364` (TTG antibody testing) is ordered to support diagnosis and monitoring.
`K52.9`	Noninfective gastroenteritis and colitis, unspecified	Symptoms prompting TTG testing when alternative causes of chronic diarrhea are considered.
`E53.8`	Other nutritional deficiencies	Used when testing for malabsorption-related deficiencies associated with suspected celiac disease.
`D50.9`	Iron deficiency anemia, unspecified	Common clinical finding that leads to evaluation for celiac disease with TTG serology.
`R19.4`	Change in bowel habit	Symptom code often accompanying order for TTG antibody testing.

Related CPT Codes

CPT Code	Description	Relationship to This Procedure
`83016`	Hemoglobin; glycosylated (A1c)	Often ordered concurrently to evaluate for metabolic contributors to symptoms or baseline chronic disease management.
`82784`	Albumin; serum	Ordered to assess nutritional status and malabsorption when celiac disease is suspected.
`86140`	Antibody; tissue transglutaminase (tTG), IgA and/or IgG (note: `86364` is the specific code in some coding sets)	Alternative or related serologic antibody testing for celiac disease; may be billed when different assay methodology or panel is used.
`43760`	Biopsy, single or multiple, during endoscopy; stomach or small intestine	Duodenal biopsy obtained during upper endoscopy is often performed after positive serology to confirm villous atrophy for definitive diagnosis.
`99213`	Office/outpatient visit, established patient, low to moderate complexity	Typical E/M visit code used when results are reviewed and management (e.g., dietary counseling, referrals) is provided following test results.