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Test ID IEHCG Interference Evaluation Heterophile, Beta-Human Chorionic Gonadotropin, Serum


Advisory Information


If "HCG Total OB" or pregnancy is indicated, order THCG / Human Chorionic Gonadotropin (hCG), Quantitative, Pregnancy, Serum.



Specimen Required


Patient Preparation: For 12 hours before specimen collection, do not take multivitamins or dietary supplements containing biotin (vitamin B7), which is commonly found in hair, skin, and nail supplements and multivitamins.

Supplies: Aliquot Tube, 5 mL (T465)

Collection Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Submission Container/Tube: Plastic vial

Specimen Volume: 2.5 mL


Useful For

Evaluation of suspected interference from heterophile antibodies causing a falsely elevated human chorionic gonadotropin (hCG) result

 

This test is not to be used for pregnancy testing.

Profile Information

Test ID Reporting Name Available Separately Always Performed
HCGII HCG, Interference Interpretation No Yes
HCGQN Beta-HCG, Quantitative, S Yes, (order BHCG) Yes
HCGAM HCG, Alternative Method, S No Yes

Testing Algorithm

Heterophile antibody evaluation consists of pretreatment with commercial heterophile antibody blocking reagents, testing on an alternate platform, and serial dilution of the sample.

Method Name

HCGQN: Electrochemiluminescent Immunoassay

HCGAM: Immunoenzymatic Assay

Reporting Name

Interference Eval, Heterophile, HCG

Specimen Type

Serum

Specimen Minimum Volume

1.5 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Refrigerated (preferred) 7 days
  Frozen  365 days
  Ambient  24 hours

Clinical Information

Some patients, due to exposure to animal antigens, have developed antibodies that interfere with immunoassay testing. These heterophilic antibodies are able to bind to animal antibodies used in immunoassays. It has been found that a significant percentage of certain sandwich immunoassay results are false-positive results caused by heterophilic antibody interference. The most commonly reported assay interference effect of heterophilic antibodies is a false-positive assay result. False-negative assay results have also been reported in the literature. Manufacturers add blocking agents to their reagents, but occasional patient samples containing heterophile antibodies are incompletely blocked. Subsequent reporting of erroneous results can have adverse effects on patient management, especially with tumor marker assays.

 

Among immunometric assays, human chorionic gonadotropin (hCG) assays have been found uniquely susceptible to heterophile antibody interference, resulting in occasional false-positive results. The current assay has proven robust in this respect, but rare interferences still occur. Typically, the observed false-positive elevations are modest, ranging from just above the reference range to levels of 50 to 60 IU/L. If such results are seen and are discordant with the clinical picture, or other biochemical or imaging tests, then the laboratory should be alerted. Repeat analysis of the specimen in question, after additional blocking treatment, may resolve the issue. Dilution of the specimen prior to assay performance often yields unexpected non-linear results in the presence of interfering substances such as heterophile antibodies. Heterophile blocking tube (HBT) treatment is used for troubleshooting samples that yield results that are either non-linear or do not match the clinical picture of the patient and are suspected of containing heterophile antibodies. Finally, assessment of an analyte such as hCG with an alternative assay will often lead to apparent discrepant results in the presence of a heterophile antibody, as heterophile antibodies often interact differently with alternative assay antibodies.

 

Human chorionic gonadotropin (hCG is a glycoprotein hormone (molecular weight [MW] approximately 36,000 Da) consisting of 2 noncovalently bound subunits. The alpha subunit (92-amino acids; "naked" protein MW 10,205 Da) is essentially identical to that of luteinizing hormone (LH), follicle-stimulating hormone, and thyrotropin (TSH). The alpha subunit is essential for receptor transactivation. The different beta subunits of the above hormones are transcribed from separate genes, show less homology, and convey the receptor-specificity of the dimeric hormones. The chorionic gonadotropin, beta gene (coding for a 145-amino acid, "naked" protein MW 15,531 Da; glycosylated subunit MW approximately 22,500 Da) is highly homologous to the beta subunit of LH and acts through the same receptor. However, while LH is a classical tropic pituitary hormone, hCG does not usually circulate in significant concentrations. In pregnant primates (including humans), it is synthesized in the placenta and maintains the corpus luteum and, hence, progesterone production, during the first trimester. Thereafter, the placenta produces steroid hormones, diminishing the role of hCG. HCG concentrations fall, leveling off around week 20, significantly above prepregnancy levels. After delivery, miscarriage, or pregnancy termination, hCG falls with a half-life of 24 to 36 hours, until prepregnancy levels are reached.

 

Outside of pregnancy, hCG may be secreted by abnormal germ cell, placental, or embryonal tissues, in particular seminomatous and nonseminomatous testicular tumors; ovarian germ cell tumors; gestational trophoblastic disease (GTD: hydatidiform mole and choriocarcinoma); and benign or malignant nontesticular teratomas. Rarely, other tumors including hepatic, neuroendocrine, breast, ovarian, pancreatic, cervical, and gastric cancers may secrete hCG, usually in relatively modest quantities.

 

During pathological hCG production, the highly coordinated secretion of alpha and beta subunits of hCG may be disturbed. In addition to secreting intact hCG, tumors may produce disproportionate quantities of free alpha-subunits or, more commonly, free beta-subunits. Assays that detect both intact hCG and free beta-hCG, including the electrochemiluminescent immunoassay  assay, tend to be more sensitive in detecting hCG-producing tumors.

 

With successful treatment of hCG-producing tumors, hCG levels should fall with a half-life of 24 to 36 hours, and eventually return to the reference range.

 

The alternate testing method is an enzymatic immunoassay. Values obtained with different assay methods or kits may be different and cannot be used interchangeably.

Reference Values

BETA-HUMAN CHORIONIC GONADOTROPIN, QUANTITATIVE, SERUM

Children(1,2)

Males

Birth-3 months: ≤50 IU/L*

>3 months-<18 years: <1.4 IU/L

Females

Birth-3 months: ≤50 IU/L*

>3 months-<18 years: <1.0 IU/L

Pediatric reference values based on:

1. Chen RJ, Huang SC, Chow SN, Hsieh CY: Human chorionic gonadotropin pattern in maternal circulation. Amniotic fluid and fetal circulation in late pregnancy. J Reprod Med. 1993;38:151-154

2. Schneider DT, Calaminus G, Gobel U: Diagnostic value of alpha 1-fetoprotein and beta-human chorionic gonadotropin in infancy and childhood. Pediatr Hematol Oncol. 2001;18:11-26

*Human chorionic gonadotropin (hCG), produced in the placenta, partially passes the placental barrier. Newborn serum beta-hCG concentrations are approximately 1/400th of the corresponding maternal serum concentrations, resulting in neonate beta-hCG levels of 10-50 IU/L at birth. Clearance half-life is approximately 2-3 days. Therefore, by 3 months of age, levels comparable to adults should be reached.

 

Adults (97.5th percentile)

Males: <1.4 IU/L

Females

Premenopausal, nonpregnant: <1.0 IU/L

Postmenopausal: <7.0 IU/L

 

HUMAN CHORIONIC GONADOTROPIN, ALTERNATIVE METHOD

Males

Birth-3 months: Not established

>3 months-49 years: <0.6 IU/L

50 years-80 years: <1.6 IU/L

>80 years: Not established

 

Females

Birth-3 months: Not established

>3 months-40 years: <0.6 IU/L

41 years-50 years: <6.2 IU/L

51 years-150 years: <7.8 IU/L

Interpretation

Specimens are evaluated for potential heterophile antibody interference in the Roche Elecsys total beta-human chorionic gonadotropin (hCG) immunoassay. Evaluation consists of pretreatment with commercial heterophile antibody blocking tube reagents, serial dilution of the sample, and testing on an alternate platform (Beckman Coulter DxI). The presence of heterophile antibody interference in the Roche Elecsys assay is not suspected when the results from the pretreatment, serial dilution, and the alternative platform agree within 20% of the original result.

 

The presence of heterophile antibody interference in the Roche Elecsys assay is suspected when 1 or more of the following are observed: a significant decrease in hCG (>20%) upon treatment of the sample with heterophile antibody blocking reagents, lack of linearity upon serial dilutions, or a significant difference in hCG concentration on the alternate platform. When a heterophile antibody interference affecting the Roche Elecsys assay is suspected, the hCG results from this assay are considered false-positive and should not be used in clinical management.

In males, hCG concentrations above the reference interval can occur if the patient is hypogonadal. Inadequate negative feedback to the pituitary, due to low sex hormone levels, may result in elevated hCG. It is recommended that serum luteinizing hormone (LH) or follicle stimulating hormone (FSH) be determined to assess this possibility.

 

Heterophile reagent blocking tubes (HBT-Scantibodies) contain a unique blocking reagent composed of specific binders, which inactivate heterophilic antibodies. Once the specific binders have bound to the heterophilic antibodies, the antibodies are no longer able to cause immunoassay interference. Blocking agents do not inhibit all heterophilic antibodies completely and cannot be used to rule out the presence of heterophile antibody interference.

For patients with apparent serum hCG concentrations greater than 15 to 20 IU/L, hCG should also be detectable in urine, if it is truly elevated. Failure to detect urinary hCG in such patients can support the suspicion of a false-positive serum hCG test.

 

After delivery, miscarriage, or pregnancy termination, hCG levels fall with a half-life of 24 to 36 hours, until prepregnancy levels are reached. An absent or significantly slower decline is seen in patients with retained products of conception.

 

Gestational trophoblastic disease (GTD) is associated with very considerable elevations of hCG, usually above 2 multiples of the median for gestational age persisting, or even rising beyond, the first trimester.

 

Serum hCG levels are elevated in approximately 40% to 50% of patients with nonseminomatous testicular cancer and 20% to 40% of patients with seminoma. Markedly elevated levels of hCG (>5000 IU/L) are uncommon in patients with pure seminoma and indicate the presence of a mixed testicular cancer.

 

Ovarian germ cell tumors (approximately 10% of ovarian tumors) display elevated hCG levels in 20% to 50% of cases.

 

Teratomas in children may overproduce hCG, even when benign, resulting in precocious pseudopuberty. Levels may be elevated to similar levels as seen in testicular cancer.

 

Among non-reproductive tumors, hepatobiliary tumors (hepatoblastomas, hepatocellular carcinomas, and cholangiocarcinomas) and neuroendocrine tumors (eg, islet cell tumors and carcinoids) are those most commonly associated with hCG production.

 

Many hCG-producing tumors also produce other embryonic proteins/antigens, in particular alpha fetoprotein (AFP). Therefore, AFP should also be measured in the diagnostic workup of such neoplasms.

 

Complete therapeutic response in hCG-secreting tumors is characterized by a decline in hCG levels with an apparent half-life of 24 to 36 hours and eventual return to concentrations within the reference range. GTD and some tumors may produce hyperglycosylated hCG with a longer half-life, but an apparent half-life of greater than 3 days suggests the presence of residual hCG-producing tumor tissue.

 

A rise in hCG levels above the reference range in patients with hCG-producing tumors that had previously been treated successfully suggests possible local or distant metastatic recurrence.

Clinical Reference

1. Cole LA, Khanlian SA, Muller CY: Detection of perimenopause or postmenopause human chorionic gonadotropin: an unnecessary source of alarm. Am J Obstet Gynecol. 2008 Mar;198(3):275.e1-7. doi: 10.1016/j.ajog.2007.09.034

2. Schneider DT, Calaminus G, Gobel U: Diagnostic value of alpha 1-fetoprotein and beta-human chorionic gonadotropin in infancy and childhood. Pediatr Hematol Oncol. 2001 Jan-Feb;18(1):11-26

3. Cole LA, Butler S: Detection of hCG in trophoblastic disease. The USA hCG reference service experience. J Reprod Med 2002 Jun;47(6):433-444

4. von Eyben FE: Laboratory markers and germ cell tumors. Crit Rev Clin Lab Sci. 2003 Aug;40(4):377-427

5. Sturgeon CM, Duffy MJ, Stenman UH: National Academy of Clinical Biochemistry laboratory medicine practice guidelines for use of tumor markers in testicular, prostate, colorectal, breast, and ovarian cancers. Clin Chem. 2008 Dec;54(12):e11-79. doi: 10.1373/clinchem.2008.105601

6. Jara-Aguirre JC, Baumann NA, Block DR, Algeciras-Schimnich A. Human chorionic gonadotropin suspected heterophile interference investigations in immunoassays: a recommended approach. Clin Chem Lab Med. 2019 Jul 26;57(8):1192-1196. doi: 10.1515/cclm-2018-1142

7. Sturgeon CM, Viljoen A. Analytical error and interference in immunoassay: minimizing risk. Ann Clin Biochem. 2011 Sep;48(Pt 5):418-32. doi: 10.1258/acb.2011.011073

8. Marks V. False-positive immunoassay results: a multicenter survey of erroneous immunoassay results from assays of 74 analytes in 10 donors from 66 laboratories in seven countries. Clin Chem. 2002 Nov;48(11):2008-2016

9. Tate J, Ward G. Interferences in immunoassay. Clin Biochem Rev. 2004 May;25(2):105-120

Day(s) and Time(s) Performed

Monday through Friday; 8 a.m.-10 p.m.

Saturday; 8 a.m.-5 p.m.

Analytic Time

1 day

Test Classification

This test has been modified from the manufacturer's instructions. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information

84702 x 2

LOINC Code Information

Test ID Test Order Name Order LOINC Value
IEHCG Interference Eval, Heterophile, HCG In Process

 

Result ID Test Result Name Result LOINC Value
HCGQN Beta-HCG, Quantitative, S 21198-7
HCGAM HCG, Alternative Method, S 21198-7
HCGIF HCG, Interference Heterophile In Process
HCGIN HCG, Interpretation In Process