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Test Code LAB4104 BETA HCG (QUANTITATIVE)

Important Note

This test is not validated for tumor marker testing. If hCG tumor marker testing is indicated, order bHCG, Tumor Marker (LAB5427). Testing will be sent to Mayo Clinic Laboratories.

Useful for:

  • Diagnosis of pregnancy
  • Investigation of suspected ectopic pregnancy
  • Monitoring of in vitro fertilization patients

Additional Codes

Labcorp 004416

Synonyms

PREGNANCY TEST, BETA, HCG, GONADOTROPHIN, HUMAN, CHORIONIC, GONADOTROPIN, PREGNANT, BHCGQ, LAB4104, BETA SUBUNIT, QUANTITATIVE

Specimen Type

Preferred Sample: Lithium Heparin Plasma (Green/Mint/Dark Green Top)
Alternative Sample: Serum (SST, Gold, Tiger, Red Top)

Specimen Volume

Preferred: 1 mL

Minimum: 0.5 mL

Sample Stability

Refrigerated: 7 days
Frozen: 1 year (≤-10°C)

Clinical Information

Human chorionic gonadotropin (hCG) is secreted by the trophoblastic cells of the placenta shortly after implantation of the fertilized ovum into the uterine wall. The rapid rise in hCG serum levels after conception makes it an excellent marker for early confirmation of pregnancy. In normal pregnancy, hCG can be detected in serum as early as 7 days following conception. The serum hCG levels increase to a peak concentration, then decrease and plateau. HCG circulates as the intact molecule in the serum of normal women who have an uncomplicated pregnancy. The subunits are cleaved rapidly and cleared by the kidney.

Limitations

  • This assay can detect whole molecule (intact) hCG and free β-hCG subunits
  • Ectopic pregnancy cannot be distinguished from normal pregnancy by hCG alone
  • The Alinity i Total β-hCG assay is cleared for use in the early detection of pregnancy only. It is not approved for any other uses such as tumor marker screening, tumor marker monitoring, etc. and it should not be performed for any other uses
  • Detection of very low levels of hCG does not rule out pregnancy. Low levels of hCG can occur in apparently healthy, nonpregnant subjects. Because hCG values double approximately every 48 hours in a normal pregnancy, patients with very low levels of hCG should be resampled and retested after 48 hours
  • Because of the high degree of sensitivity of the assay, specimens tested as positive during initial days after conception may later be negative due to natural termination, which occurs in 22% of clinically unrecognized pregnancies and 31% of pregnancies overall
  • Infrequently, hCG levels may appear consistently elevated and could be due to, but not limited to, the presence of the following: heterophilic antibodies, nonspecific protein binding, hCG-like substances, trophoblastic or non-trophoblastic neoplasms.

Method

Chemiluminescent Microparticle Immunoassay (CMIA)

 

This assay is a two-step immunoassay for the quantitative and qualitative determination of β-hCG in serum and plasma using chemiluminescent microparticle immunoassay (CMIA) technology. Sample and anti-β-hCG coated paramagnetic microparticles are combined and incubated. The β hCG present in the sample binds to the anti-β-hCG coated microparticles. The mixture is washed. Anti-β-hCG acridinium-labeled conjugate is added to create a reaction mixture and incubated. Following a wash cycle, Pre-Trigger and Trigger Solutions are added. The resulting chemiluminescent reaction is measured as relative light units (RLUs). There is a direct relationship between the amount of β-hCG in the sample and the RLUs detected by the system optics.

Turnaround Time

STAT: 1 hour
Routine: 4 hours

Reference Ranges

 <5.00 mIU/mL

 

Measuring range: 2.42-15000.00 mIU/mL

Reporting range: 2.42-225000.00 mIU/mL (1:15 dilution)

Test Schedule

Daily

CPT Codes

84702