CPT 84305: Somatomedin (IGF) Blood Assay

Headline: CPT code 84305 — Somatomedin (IGF) blood assay important for endocrine and metabolic evaluation

Lead: CPT code 84305 identifies a laboratory assay measuring somatomedin in blood. The test informs clinical evaluation of growth hormone activity and related metabolic conditions and is commonly ordered in endocrine and pediatric contexts.

What it represents and why it matters nationally: CPT code 84305 designates a somatomedin (insulin-like growth factor) blood test performed by a laboratory analyst. This diagnostic measurement supports evaluation of growth disorders, suspected growth hormone deficiency or excess, and certain metabolic assessments. As a routine component of endocrine workups, it has relevance across outpatient and inpatient laboratory services nationwide.

Key payers covered: Analysis includes major national commercial and public payers: Aetna; Blue Cross Blue Shield; Cigna Health; UnitedHealthcare; and Medicare.

What readers will learn: The publication provides clinical context for when CPT code 84305 is used, compares related laboratory tests, and outlines common care settings for the service. Readers will find benchmark comparisons, billing considerations tied to laboratory service lines, and policy or coverage notes relevant to national payers. The content summarizes typical clinical indications, how this test integrates with lipid and metabolic panels, and where CPT code 84305 fits within laboratory diagnostic workflows.

Billing Code Overview

CPT code 84305 describes a laboratory assay performed by a clinical laboratory analyst to measure the hormone somatomedin (commonly known as insulin-like growth factor) in a patient blood specimen. This service is a laboratory diagnostic test used to assess somatomedin levels for clinical evaluation related to growth hormone activity and metabolic status.

The service type is a clinical laboratory diagnostic assay. The typical site of service is a clinical laboratory or hospital laboratory setting where blood specimens are analyzed.

Clinical Context

A 52-year-old patient with a history of mixed hyperlipidemia (E78.2) and long-term lipid-lowering therapy (Z79.899) presents to a family medicine clinic for routine cardiovascular risk assessment and medication monitoring. The clinician orders laboratory studies including a lipid panel and an endocrine assessment because the patient reports persistent fatigue and there is concern for altered growth factor status that may affect metabolism. A phlebotomy technician draws a blood specimen; the sample is sent to the clinical medical laboratory where a lab analyst performs the test to measure somatomedin (insulin-like growth factor), reported under CPT 84305. The lab documents specimen collection time, handling conditions, and analytic method. Results are transmitted to the ordering provider (family medicine or internal medicine) via the electronic health record; the clinician reviews CPT 84305 results alongside related lipid studies to interpret metabolic and endocrine contributors to the patient’s cardiovascular risk profile.

Coding Specifications

Modifier	Description	When to Use
`26`	Professional component

Taxonomy Code	Specialty	Notes
`291U00000X`	Clinical Medical Laboratory	Performing laboratory that conducts `CPT 84305` testing and reports the technical component.
`207Q00000X`	Family Medicine Physician	Common ordering provider for metabolic and cardiovascular risk assessment including somatomedin testing.
`207R00000X`	Internal Medicine Physician	Common ordering provider for endocrine evaluation and chronic disease management involving this test.

Related Diagnoses

ICD-10 Code	Description	Clinical Relevance
`E78.0`	Pure hypercholesterolemia	Elevated LDL cholesterol may prompt evaluation of metabolic contributors; somatomedin testing can be part of broader endocrine assessment.
`E78.5`	Hyperlipidemia, unspecified	General dyslipidemia diagnosis where clinicians may order lipid panels and adjunct endocrine tests including somatomedin.
`Z13.220`	Encounter for screening for lipoid disorders	Screening visit during which providers may order `CPT 84305` alongside lipid studies for comprehensive risk assessment.
`E78.2`	Mixed hyperlipidemia	Presence of mixed lipid abnormalities often triggers combined lipid and endocrine testing to guide therapy.
`Z79.899`	Other long term (current) drug therapy	Indicates long-term medication use (e.g., statins) where monitoring and additional testing such as somatomedin measurement may be performed to assess metabolic effects.

Related CPT Codes

CPT Code	Description	Relationship to This Procedure
`80061`	Lipid panel	Often ordered concurrently to evaluate cholesterol fractions and cardiovascular risk alongside `CPT 84305`.
`84478`	Triglycerides	Component of lipid assessment that may be ordered with somatomedin measurement for metabolic evaluation.
`83718`	Lipoprotein, direct measurement; high density cholesterol (HDL)	HDL measurement frequently accompanies `CPT 84305` in dyslipidemia workups.
`82465`	Cholesterol, serum, total	Basic cholesterol assessment commonly performed with endocrine/metabolic testing such as `CPT 84305`.

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Summary & Overview