HCG Quantitative

Test Code

HCGQT

Preferred Specimen

Specimen Type: Serum
Collection Container: Serum gel
Specimen Volume: 3 mL

Minimum Volume

0.10 mL

Other Acceptable Specimens

Specimen Type: Plasma
Collection Container: Green top (Lithium heparin)

Instructions

Centrifuge and separate cells within 4 hours of collection.

Transport Container

Plastic vial

Specimen Stability

Room temperature: 24 hours
Refrigerated on gel: 24 hours
Refrigerated off gel: 7 days
Frozen: 12 months

Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)

Specimens stored on gel >24 hours, unlabeled, mislabeled, wrong tube type, QNS

Methodology

Chemiluminescent Microparticle Immunoassay (CMIA)

Setup Schedule

Daily

Report Available

Same day

Limitations

As with any immunochemical reaction, unknown interferences from medications or endogenous substances may affect results.

Interfering substances (such as heterophile antibodies, non-specific proteins, or hCG-like substances) may falsely depress or falsely elevate results. These interfering substances may cause false results over the entire range of the assay, not just at low levels, and may indicate the presence of hCG when there is none.

If the hCG level is inconsistent with, or unsupported by, clinical evidence, results should be confirmed by an alternate hCG method. This may include the qualitative testing of urine. The absence of urinary hCG may suggest a falsely elevated serum result. Results may also be confirmed by performing serial dilutions of the sample. Usually, but not always, samples that contain interfering substances exhibit nonlinear results when diluted.

Detection of very low levels of hCG does not rule out pregnancy. Low levels of hCG can occur in apparently healthy, non-pregnant subjects. Because hCG values double approximately every 48 hours in a normal pregnancy, patients with very low levels of hCG should be re-sampled and retested after 48 hours.

Post-menopausal specimens may elicit weak positive results due to low hCG levels unrelated to pregnancy. With a weak positive result, it is good laboratory practice to resample and retest after 48 hours, or to test with an alternate hCG method.

Elevated hCG levels have been associated with some abnormal physiological states (e.g., trophoblastic and non-trophoblastic neoplasms) and the results of this test should not be used in the diagnosis of these abnormal states. There have been reports of people receiving unnecessary medical treatment and surgery, including chemotherapy and hysterectomy, when hCG results were used in the diagnosis of abnormal states.

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 of the pregnancy. Natural termination occurs in 22% of clinically unrecognized pregnancies and 31% of pregnancies overall. It is good laboratory practice to re-sample and retest weak positive results after an additional 48 hours.

Do not use this assay for TUMOR DETECTION.

** If the specimen is centrifuged BEFORE a complete clot forms, the presence of fibrin may cause erroneous results. **

Reference Range

See laboratory report

Clinical Significance

Human chorionic gonadotropin (hCG) is a sialoglycoprotein with a molecular weight of approximately 46,000 Daltons. HCG is initially 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 and monitoring of pregnancy.

Physiologically, hCG appears to maintain the corpus luteum, thereby allowing synthesis of progesterone and estrogens that support the endometrium. As uncomplicated pregnancies progress, the placenta assumes the production of these hormones. 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.

With the availability of sensitive quantitative assays for the measurement of serum Beta-hCG, it has been shown that hCG levels can be useful in prediction of spontaneous abortions, aiding in the detection of ectopic pregnancy and in multiple gestations.

The Alinity Total β–hCG assay is cleared for use in the early detection of PREGNANCY ONLY.

Performing Laboratory
Inova Laboratories
2832 Juniper Street
Fairfax, VA 22031

Last Updated: March 3, 2023
Last Review: N. Wolford, March 3, 2023

The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.