UCSF Navigation Bar

UCSF Departments of Pathology & Laboratory Medicine Home Page

Lab Manual for UCSF Clinical Laboratories

Lab Manual for SFGH

Internal Resources


Item Value
Available Stat? Yes
Test code HCG (previously BHCG)
Performed by? Chemistry
Sendout? no
Price range $$$
In House Availability Routine: 7 days;
STAT: 24 hours/ 7 days
Principle The Siemens Centaur assay is a two-site sandwich immunoassay using direct chemiluminometric technology.
Interpretation HCG measurement is used in identifying women with ectopic pregnancies or abnormal intrauterine pregnancies. Values below those expected will be found in threatened abortion and ectopic pregnancy. HCG is normally undetectable (< 5 IU/L) in healthy males and healthy non-pregnant females. Persistent low levels of HCG have been reported in postpartum and postmenopausal states. Results for HCG and HCG variants may be significantly different when measured at different laboratories due to variation in assays. Serial testing for HCG (e.g., every 48 hours to monitor pregnancy) should always be performed by a single laboratory to avoid misleading or anomalous results.

Elevated serum HCG levels are also found in patients with trophoblastic diseases (including complete and partial hydatidiform mole, post-molar tumor, gestational choriocarcinoma, testicular choriocarcinoma, and placental site trophoblastic disease). Additionally, elevated HCG levels have been reported in patients with other malignancies such as lung, prostate, and breast cancers. Note that this test is FDA-approved only for monitoring pregnancy and thus may not detect the various different forms of HCG that may be produced by trophoblastic diseases and tumors. This assay detects both intact HCG and free complete beta subunits; ability to detect alternate forms of beta subunits has not been characterized. False negative and false positive results have been reported in patients with known or suspected trophoblastic disease. Please contact the laboratory if there is discordance between clinical and laboratory findings.
Container type gold top gel tube
Amount to Collect 2 mL
Collection Instructions Plasma samples cannot be assayed.
Sample type Blood
Normal range < 5 IU/L (in healthy males and healthy non-pregnant females)

Normal Pregnancy, Time Post Implantation*:

0.2 – 1 Week 5-50 IU/L 4 – 5 Weeks 1,000-50,000 IU/L
1 – 2 Weeks 50-500 IU/L 5 – 6 Weeks 10,000-100,000 IU/L
2 – 3 Weeks 100-5,000 IU/L 6 – 8 Weeks 15,000-200,000 IU/L
3 – 4 Weeks 500-10,000 IU/L 2 – 3 Months 10,000-100,000 IU/L

* Units are referenced to WHO 3rd International Standard (3rd IS 75/537) reference material.
Synonyms Beta-Human Chorionic Gonadotropin (BHCG);HCG;
Stability 48 hours at 2-8°C. 1 month at -20°C.
Interferences 1. Presence of heterophilic antibodies may yield either falsely elevated or falsely depressed values. Examples of these antibodies include (but are not limited to):

a. Patients receiving preparations of mouse monoclonal antibodies for therapy or diagnosis may develop anti-mouse antibodies (i.e. HAMA – Human Anti-Mouse Antibodies).

b. Patients with significant levels of rheumatoid factor (RF).

2. Due to structural similarity, high levels of luteinizing hormone (LH), follicle-stimulating hormone (FSH), and thyroid stimulating hormone (TSH) may have low-level cross-reactivity with this assay and yield falsely elevated or depressed values.

3. A paradoxical, false low result may rarely occur when patient samples with extremely high concentrations of peptide/protein analytes (e.g. AFP, hCG, PSA, etc.) are measured by immunometric ("two-site," "sandwich") assays. For example, a true value of 3,000,000 U/L could be reported as < 5 or 21 U/L. This phenomenon is called the "high dose hook effect." Results inconsistent with clinical findings or previous laboratory values can be investigated by the laboratory for this phenomenon. Call the Clinical Chemistry Laboratory Medicine Resident (x65527, pager 415-443-2311).
Additional information INDICATIONS: Evaluation of ectopic and abnormal intrauterine pregnancies
References 1. Cole L. Immunoassay of human chorionic gonadotropin, its free subunits, and metabolites, Clin Chem 43(12): 2233-43, 1997.

2. Cole LA, et al. Utility of commonly used commercial human chorionic gonadotropin immunoassays in the diagnosis and management of trophoblastic diseases, Clin Chem 47(2): 308-15, 2001.

3. DiPietro DL. Ectopic pregnancy: interpreting HCG levels, Lab Management 19:11, 1981.

4. Kosasa TS. Measurement of human chorionic gonadotropin, J Reprod Med 26:201, 1981.

5. ADVIA Centaur Assay Manual 117559 Rev. F, Siemens Medical Solutions Diagnostics, Malvern, PA.

6. Dufour, DR. "Background" human chorionic gonadotropin in healthy, nonpregnant women. Clin Chem, 2005; 51:1765-1766.

7. Snyder, JA; Haymond, S; Parvin, CA; Gronowski, AM; Grenache, DG. Diagnostic considerations in the measurement of human chorionic gonadotropin in aging women. Clin Chem, 2005; 51:1830-1835.
CPT coding 84702
Last Updated 6/18/2011 8:31 AM
Search Our Test Menu
UCSF home page UCSF home page About UCSF Search UCSF UCSF Medical Center