DEPARTMENT OF OBSTETRICS AND GYNECOLOGY
 UNIVERSITY OF NEW MEXICO

USA HCG REFERENCE SERVICE
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   The hCG test or pregnancy test is one of the most common immunoassays run in clinical laboratories today (click here for principal of hCG test and causes of discordant results).    

    It is assumed that an hCG assay detects only hCG or hCGß. This is not the case. hCG kits can detect a wide and varying range of different hCG-related molecules in serum or urine samples. These include abnormally synthesized hCG molecules and hCG degradation products (click here to see illustration of the synthesis and degradation of hCG). The molecules detected include non-nicked hCG ("hCG") the active hormone, nicked or cleaved hCG, hyperglycosylated or carbohydrate variant hCG (also known as ITA or Invasive Trophoblast Antigen), asialo hCG (missing sialic acid), hCG missing the ß-subunit C-terminal extension, a large and a regular free alpha-subunit, a nicked and a non-nicked free ß-subunit, and ß-core fragment (references 1-5, below).    

    hCG is the major hCG-related molecule present in serum and ß-core fragment the principal hCG-related molecule in urine samples in normal pregnancies. Nicked hCG, hyperglycosylated hCG, asialo hCG, hCG-CTP or free ß-subunit can, in some cases, become the dominant hCG form. This may happen while hCG levels are clearing postpartum, in very early pregnancies (week following implantation), in aneuploid or Down syndrome pregnancies, in failing pregnancies, in hydatidiform mole and choriocarcinoma cases, or in non-pregnant individuals (references 3-6, below). Most commercial hCG kits used in clinical laboratories do not detect nicked hCG or hCG-CTP, or hyperglycosylated hCG, free ß-subunit and/or ß-core fragment. This causes discordance in assay results, false-negative or unduly low hCG results (click here for principal of hCG test and causes of discordant results). This complicates the widely varying individual hCG levels detected in serum during pregnancy (click here to see data on hCG levels during normal pregnancy). While minor variations are noted in different hCG kit results with samples from normal pregnancy (<2-fold inter-assay variation in serum, <7-fold variation in urine), more major variations are found in samples from abnormal pregnancies, aborting pregnancies, Down syndrome and genetically abnormal pregnancies, in cancers that produce hCG, and in hydatidiform moles (molar pregnancies), persistent trophoblast disease or choriocarcinoma (up to 55 fold variation in different hCG tests) (references 2-4, below) (click here to see potential sources of hCG in and outside of pregnancy). Erroneous hCG test results have led to needless surgery, misdiagnosis of trophoblast disease, false pregnancy test results, and unwarranted patient concern.

    The hCG Reference Service investigates the nature of the hCG present in serum and urine samples (intact hCG, nicked hCG, hyperglycosylated or carbohydrate-variant hCG, asialo hCG, free ß-subunit or ß-core fragment). From the nature of the hCG in serum and urine, published information and our data bank, inferences are made about the origin of the hCG-related molecules (pregnancy, benign trophoblast disease, persistent trophoblast disease or choriocarcinoma, pituitary hCG, germ cell or other cancer, phantom or false-positive hCG).

    Many cases with invalid, false positive or phantom hCG results have been now been identified by the USA hCG Reference Service.  In these case, human antibodies against human antibodies may cross cross-species (heterophilic antibodies) interfering with hCG test results. Similarly, human antibodies against animal antibodies may interfere with the animal antibodies used in hCG tests (click here to see the principal of false positive or phantom hCG tests). False positive or phantom hCG tests have led to the misdiagnosis of ectopic pregnancy, or to the erroneous assumption of post-gestational choriocarcinoma. A relatively large number of patient have been and are still being needlessly treated with chemotherapy and received a hysterectomy or other surgical procedures based solely on false or phantom hCG levels (see references 7-13, below) (click here to see potential sources of hCG in and outside of pregnancy). The USA hCG Reference Service experience with a large number of cases of women with false positive hCG results, and the needless chemotherapy or surgery the received, is now described in an attached article (hCG Reference Service Report 2002).

    We have now observed a large number of women with persistent low levels of REAL hCG (sometimes referred to as "Quiescent Gestational Trophoblast Disease" and "Unexplained Elevated hCG.) In each of these cases low levels of real hCG have been identified. The low levels may persist for as long as 6 years. In each syndrome chemotherapy and hysterectomy have been tried needlessly without success. In each case no pregnancy or tumor is identified. The USA hCG Reference Service experience with these syndrome, and the experience of Trophoblast Diseases Centers is described in the attached urgent report (URGENT REPORT: Persistent low levels of REAL hCG) and in the attached article (hCG Reference Service Report 2001).   

    The hCG Reference Service is a consulting service. It was started to address these issues, aid in the interpretation of irregular or conflicting hCG results, help interpret low levels of hCG in non-pregnant individuals, and in individuals with trophoblast disease (hydatidiform mole and choriocarcinoma). It was also started to detect false-positive or phantom hCG results, and hCG of pituitary or cancer origin.
    The following issues are commonly addressed by the hCG Reference Service -

Unexplained Persistent low levels of hCG in those with history of trophoblastic diseases (quiescent gestational trophoblastic disease).

Unexplained Persistent low levels of hCG in those with no history of trophoblastic diseases (unexplained elevated hCG).

Identification of phantom or false positive hCG immunoreactivity in those with no pregnancy, assumingly diagnosed with ectopic pregnancy or gestational trophoblastic disease/choriocarcinoma.

Identification of hCG of cancer origin.

Confirmation of trophoblast disease hCG .

Conflicting hCG test data, false negative hCG data, hCG detected in serum but not urine or vice versa.

    The hCG Reference Service requires a parallel serum and urine sample. This should be shipped by overnight service with coolant (click here for instructions on referring a patient to the hCG Reference Service). The samples are tested in 30 to 50 specialized hCG and related molecule tests measuring hCG and hCG-related molecules (click here to see description of specialized tests at hCG Reference Service).  A letter is required from a physician or clinical laboratory requesting the hCG Reference Service. The letter should summarize the patient's medical and hCG test history. Insurance or billing information must also be submitted (click here for instructions on referring a patient to the hCG Reference Service).
    For further information, or to submit samples, contact the hCG Reference Service.

Laurence A. Cole, Ph.D.
hCG Reference Service
Room 4198, 4th floor ACC
Department of Obstetrics & Gynecology,
University of New Mexico Health Center
2211 Lomas Boulevard, NE
Albuquerque, New Mexico 87131

Telephone: (505) 272-6137,
Fax: (505) 272-6385,
E-mail: larry@hcglab.com         

Click here for further information on Laurence A. Cole, Ph.D.

    We list other important contacts, specialist in the treatment and management of trophoblast disease around the world, and other experts on hCG immunoassays and immunoassay limitations (click here for other important contacts).

REFERENCES

1. Elliott M, Kardana A, Lustbader J, Cole L. Carbohydrate and peptide structure of the alpha- and beta-subunits of hCG from normal and aberrant pregnancy and choriocarcinoma. Endocrine 7:15-32, 1997.

2. Cole L. Immunoassay of hCG, its Free Subunits and Metabolites. Clin Chem 43:2233-2243, 1997.

3. Cole L. hCG, free beta subunit (free ß), free alpha-subunit (free alpha) and ß-core fragment (ß-core). Diagn. Endocrinol. Metab., 15:199-220, 1997

4. Cole L, Kohorn E, Kim G. Detecting and monitoring trophoblast disease: New perspectives in measuring hCG levels. J Reprod. Med. 39:193-200, 1994.

5. Alfthan H, Stenman U. Pathophysiological importance of various molecular forms of hCG. Mol Cell Endocrinol 125(1-2):107-20, 1996.

6. Birken S, Maydelman Y, Gawinowicz M, Pound A, Liu Y, Hartree A. Isolation and characterization of human pituitary chorionic gonadotropin. Endocrinology 137:1402-1411, 1996.

7. Cole LA. Phantom hCG and phantom choriocarcinoma. Gynecol Oncol, 71:325-329, 1998.

8. Cole, L.A., Rinne, K.M., Shahabi, S., and Omrani, A. False positive hCG levels leading to unnecessary surgery and chemotherapy, and needless occurrences of diabetes and coma. Clin Chem, 45:313-314, 1999.

9. Cole, L.A., Shahabi, S., Butler, S., Mitchell, H., Newlands, E.S., Behrman, H.R., Verrill, H.L. Utility of commonly used commercial hCG immunoassays in the diagnosis and management of trophoblastic diseases. Clin Chem 47:308-315, 2001.

10. Cole, L.A. and Butler S.A., hCG, its Free Subunits and Metabolites in Trophoblastic Diseases. J. Reprod. Med. 47:433-444, 2002.

11. Butler S.A., Cole, L.A. Falsely elevated hCG leading to unnecessary therapy Obstet Gynecol, 99:515-516, 2002.

12. Cole LA. Use of hCG Tests for Evaluating Trophoblastic Diseases: Choosing an Appropriate hCG Assay, False Detection of hCG, Unexplained Elevated hCG, and Quiescent Trophoblastic Disease. In: Gestational Trophoblastic Disease, 2nd Edition (Eds: Hancock BW, Newland ES, Berkowitz RS), Chapman and Hall, London, in press, 2002.

13.  Olsen TG, Hubert PR, Nycum LR. Falsely elevated human chorionic gonadotrophin leading to unnecessary therapy.  Obstet Gynecol  98:843-845, 2001.

 

hCG Reference Service HOME PAGE
introduction to hCG and the hCG Reference Service

hCG Reference Service Report 2002
medical report on the experience of the hCG Reference Service, 1997-2002,with patient with false positive hCG results, and with persistent low levels of REAL hCG (quiescent gestational trophoblastic disease and unexplained elevated hCG). The report also examines and compares the performance of professional laboratory hCG tests.

URGENT REPORT Persistent low levels of hCG
URGENT REPORT on patients with persistent low concentrations of real hCG with no pregnancy or evidence of tumor

Principal of hCG test and causes of discordant results 
how the hCG test works and why sometimes it gives discord or erroneous results

Synthesis and degradation of hCG
the production of hCG in trophoblast cells, abnormal production, and dissociation, nicking and degradation of hCG after secretion

Specialized tests at hCG Reference Service
the specialized hCG assays run by the hCG Reference Service to help identify the source and nature of hCG

False positive of phantom hCG tests
false positive or phantom hCG tests, the mechanisms that cause hCG assays to give mistaken results, and the potentially devastating clinical consequences

Potential sources of hCG in and outside of pregnancy
the biological sources of hCG: normal pregnancy, early pregnancy loss, ectopic pregnancy, gestational Down syndrome, hydatidiform mole and choriocarcinoma cells, germ cell and other non-trophoblastic malignancies; pituitary hCG production, and phantom or false-positive hCG

hCG levels during normal pregnancy
the widely varying hCG levels observed during the course of normal pregnancy

Refer a patient to the hCG Reference Service
how to seek help from or refer a patient to the hCG Reference Service, the samples needed and patients history and insurance requirements

About Laurence A. Cole, Ph.D.
curriculum vitae of Laurence A. Cole, Ph.D., Director of the hCG Reference Service

Other important contacts
centers throughout the world specializing in the treatment of Trophoblastic Diseases and laboratories and scientists with expert knowledge in the endocrinology, chemistry and testing for hCG