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Official Description

Gonadotropin, chorionic (hCG); free beta chain

© Copyright 2026 American Medical Association. All rights reserved.

Common Language Description

The CPT® Code 84704 refers to the measurement of free beta chain human chorionic gonadotropin (hCG) levels through a blood sample. Human chorionic gonadotropin is a glycoprotein that plays a crucial role in pregnancy, being secreted by the trophoblast cells of the placenta. This hormone consists of two subunits: the alpha hCG and the beta hCG. During pregnancy, both subunits are typically elevated in the bloodstream, serving as important indicators of the body's physiological changes. The free beta chain of hCG is particularly significant, as its elevated levels during the first trimester can serve as a specific and sensitive diagnostic marker for various conditions. These include gestational trophoblastic neoplasms, such as hydatidiform mole and choriocarcinoma, as well as chromosomal abnormalities like Down syndrome and trisomy 18, and developmental issues such as neural tube defects. The testing process for free beta chain hCG involves a two-step methodology that utilizes two high-affinity monoclonal antibodies within an immunoradiometric assay (IRMA) system, ensuring accurate measurement of this important biomarker.

© Copyright 2026 Coding Ahead. All rights reserved.

1. Indications

The measurement of free beta chain human chorionic gonadotropin (hCG) levels is indicated for several clinical scenarios, particularly in the context of pregnancy and related conditions. The following are the specific indications for performing this test:

  • Gestational Trophoblastic Neoplasms Elevated levels of free beta chain hCG can indicate the presence of gestational trophoblastic neoplasms, including hydatidiform mole and choriocarcinoma.
  • Down Syndrome The test is utilized as a screening tool for Down syndrome, where elevated hCG levels may suggest an increased risk.
  • Trisomy 18 Similar to Down syndrome, elevated free beta chain hCG levels can be associated with trisomy 18, prompting further investigation.
  • Neural Tube Defects The measurement of free beta chain hCG is also relevant in assessing the risk of neural tube defects during early pregnancy.

2. Procedure

The procedure for measuring free beta chain hCG levels involves a systematic approach to ensure accurate results. The following steps outline the process:

  • Step 1: Blood Sample Collection A blood sample is obtained from the patient, typically through venipuncture. This sample serves as the basis for the subsequent analysis of free beta chain hCG levels.
  • Step 2: Immunoradiometric Assay (IRMA) The collected blood sample undergoes testing using a two-step immunoradiometric assay (IRMA) system. This method employs two high-affinity monoclonal antibodies that specifically bind to the free beta chain of hCG, allowing for precise measurement of its concentration in the blood.

3. Post-Procedure

After the blood sample has been collected and analyzed, the results are typically available within a specified timeframe, depending on the laboratory's processing capabilities. Patients may be advised to follow up with their healthcare provider to discuss the results and any necessary next steps. It is important to note that elevated levels of free beta chain hCG may require further diagnostic evaluation or monitoring, particularly in the context of the conditions indicated. Additionally, patients should be informed about any potential symptoms or signs that may warrant immediate medical attention following the test.

Short Descr HCG FREE BETACHAIN TEST
Medium Descr GONADOTROPIN CHORIONIC HCG FREE BETA CHAIN
Long Descr Gonadotropin, chorionic (hCG); free beta chain
Status Code Statutory Exclusion (from MPFS, may be paid under other methodologies)
Global Days XXX - Global Concept Does Not Apply
PC/TC Indicator (26, TC) 9 - Not Applicable
Multiple Procedures (51) 9 - Concept does not apply.
Bilateral Surgery (50) 9 - Concept does not apply.
Physician Supervisions 09 - Concept does not apply.
Assistant Surgeon (80, 82) 9 - Concept does not apply.
Co-Surgeons (62) 9 - Concept does not apply.
Team Surgery (66) 9 - Concept does not apply.
Diagnostic Imaging Family 99 - Concept Does Not Apply
CLIA Waived (QW) No
APC Status Indicator Conditionally packaged laboratory tests
Type of Service (TOS) 5 - Diagnostic Laboratory
Berenson-Eggers TOS (BETOS) T1H - Lab tests - other (non-Medicare fee schedule)
MUE 1
CCS Clinical Classification 233 - Laboratory - Chemistry and Hematology
90 Reference (outside) laboratory: when laboratory procedures are performed by a party other than the treating or reporting physician or other qualified health care professional, the procedure may be identified by adding modifier 90 to the usual procedure number.
XU Unusual non-overlapping service, the use of a service that is distinct because it does not overlap usual components of the main service
Date
Action
Notes
2011-01-01 Changed Short description changed.
2008-01-01 Added First appearance in code book in 2008.
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Description
Code
Description
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