TEST CATALOG ORDERING & RESULTS SPECIMEN HANDLING CUSTOMER SERVICE EDUCATION & INSIGHTS
Test Catalog

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

Useful For Suggests clinical disorders or settings where the test may be helpful

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.

Testing Algorithm Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

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

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

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 Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

BETA-HUMAN CHORIONIC GONADOTROPIN, QUANTITATIVE, SERUM

Children(1,2)

Males

Birth-3 months: < or =50 IU/L*

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

Females

Birth-3 months: < or =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 Provides information to assist in interpretation of the test results

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.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Values obtained with different assay methods or kits may be different and cannot be used interchangeably.

 

Test results cannot be interpreted as absolute evidence for the presence or absence of malignant disease.

 

This heterophile antibody interference evaluation does not rule out the presence of other types interfering substances such as biotin.

 

There may be some samples with extremely strong heterophilic interference. In such cases heterophile blocking reagents may not be able to block all of the assay interference.

Despite strenuous efforts at standardization, different human chorionic gonadotropin (hCG) assays show only modest agreements with each other. Therefore, whenever serial monitoring of hCG concentrations is required, the same assay should be used for all measurements.

 

Transient elevations of serum hCG can occur following chemotherapy in patients with susceptible tumors, due to massive tumor cell lysis; these transient elevations should not be confused with tumor progression.

 

Normal serum levels of hCG do not always exclude tumor persistence since tumors may undergo transition to differentiated teratomas, which may not produce hCG.

 

In individuals with incomplete or complete primary hypogonadism (eg, menopausal women, XXY males, surgically or medically castrated individuals who are receiving inadequate sex steroid replacement therapy), increased luteinizing hormone (LH)-gene transcription results in minor "leaky" transcription of hCG and hCG levels of 3 to 5 IU/L, and in some cases, levels as high as 25 IU/L may be seen. In postmenopausal women hCG levels ranging from 3.5 to 32 IU/L have been reported. In these cases measurement of serum concentrations of sex hormones (LH and follicle stimulating hormone) might be indicated.

 

End-stage renal failure is associated with up to 10-fold elevations in serum hCG levels.

 

In rare cases, interference due to extremely high titers of antibodies to analyte-specific antibodies, streptavidin or ruthenium can occur. The laboratory should be alerted if hCG values do not correlate with the clinical presentation.

Clinical Reference Recommendations for in-depth reading of a clinical nature

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