Discordant results in human chorionic gonadotropin assays.

Discordance has been reported in human chorionic gonadotropin (hCG) concentrations measured by different immunoassay kits. We examined the results for 40 serum samples assayed with 10 different hCG immunoassay kits. Results varied considerably. Individual sample results varied by as much as 58-fold. Average results for different kits varied by as much as 1.4-fold for pregnancy (20 samples) and 2.2-fold for trophoblast disease (20 samples) serum. We investigated the causes of this discordance. hCG or hCG beta are general names for mixtures of hCG, hCG alpha, or hCG beta immunoreactive molecules in serum. These mixtures include regular hCG, nicked hCG (missing peptide linkages at beta 44-45 or beta 47-48), carbohydrate variants of hCG, hCG missing the beta-subunit C-terminal segment, free beta-subunit, beta-core fragment, and free alpha-subunit. We prepared standards for each of these major variants and measured their reactivities in the 10 hCG immunoassay kits. Free beta-subunit reactivity varied from nonrecognition (anti-beta:anti-alpha type kits; Hybritech Tandem-R and others) to overrecognition (one kit had five-fold greater affinity for free beta than for hCG). Kits with antibodies to beta-subunit C-terminal segment (Organon NML and others) failed to recognize hCG missing this segment, a component of serum hCG in trophoblast disease. Kits with anti-hCG antibodies (Serono MAIA-clone and others) had minimal recognition of nicked hCG (12%), a component of all serum hCG samples, and consistently gave the lowest values with all serum samples. We conclude that differences in recognition of nicked hCG, free beta, and these other hCG variants cause discordance in hCG immunoassay results.     

Establishment, value assignment, and characterization of new WHO reference reagents for six molecular forms of human chorionic gonadotropin

BACKGROUND: The International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) established a Working Group to investigate means of improving the comparability of immunoassays for human chorionic gonadotropin (hCG), which was selected as a prototype glycoprotein analyte. The Working Group identified development of unambiguous nomenclature and production of new highly purified International Reference Reagents calibrated in substance concentrations as its primary objectives. METHODS: Preparations of intact hCG, nicked hCG, hCG beta-subunit, nicked hCG beta-subunit, hCG alpha-subunit, and hCG beta-core fragment were purified from a crude urinary hCG preparation, ampouled, lyophilized, and assigned values in substance concentrations (mol/L). Value assignment and accelerated degradation studies were carried out in accordance with WHO protocols for International Reference Reagents. RESULTS: The ampouled standards were assigned final values based on the recovery of immunoreactive material after reconstitution. The degradation studies showed that the standards were highly stable. CONCLUSIONS: The nomenclature of hCG-related molecules and immunoassays has been adopted by the IFCC, and the standards prepared and characterized by the Working Group have been formally adopted by the WHO as the First International Reference Reagents for six hCG-related molecules. These developments will enable better understanding of what assays for hCG measure and should ultimately help to improve the clinical application of these assays.     

Utility of commonly used commercial human chorionic gonadotropin immunoassays in the diagnosis and management of trophoblastic diseases

BACKGROUND: Patients with trophoblastic diseases produce ordinary and irregular forms of human chorionic gonadotropin (hCG; e.g., nicked hCG, hCG missing the beta-subunit C-terminal segment, hyperglycosylated hCG, and free beta subunit) that are recognized to differing extents by automated immunometric hCG (or hCG beta) assays. This has led to low or false-negative results and misdiagnosis of persistent disease. False-positive hCG immunoreactivity has also been detected, leading to needless therapy for trophoblastic diseases. Here we compare seven commonly used hCG assays. METHODS: Standards for five irregular forms hCG produced in trophoblastic diseases, serum samples from 59 patients with confirmed trophoblastic diseases, and serum samples from 12 women with previous false-positive hCG results (primarily in the Abbott AxSYM assay) were blindly tested by commercial laboratories in the Beckman Access hCG beta, the Abbott AxSYM hCG beta, the Chiron ACS:180 hCG beta, the Baxter Stratus hCG test, the DPC Immulite hCG test, the Serono MAIAclone hCG beta tests, and in the hCG beta RIA. RESULTS: Only the RIA and the DPC appropriately detected the five irregular hCG standards. Only the Beckman, DPC, and Abbott assays gave results similar to the RIA in the patients with confirmed trophoblastic diseases (values within 25% of RIA in 49, 49, and 54 of 59 patients, respectively). For samples that were previously found to produce false-positive hCG results, no false-positive results were detected with the DPC and Chiron tests (5 samples, median <2 IU/L), but up to one-third of samples were false positive (>10 IU/L) in the Beckman (1 of 5), Serono (2 of 9), and Baxter assays (1 of 5), and the hCG beta RIA (3 of 9; median for all assays, <5 IU/L). These samples, which produced false-positive results earlier in the Abbott AxSYM assay, continued to produce high values upon reassessment (median, 81 IU/L). CONCLUSIONS: Of six frequently used hCG immunometric assays, only the DPC detected the five irregular forms of beta hCG, agreed with the RIA, and avoided false-positive results in the samples tested. This assay, and similarly designed assays not tested here, seem appropriate for hCG testing in the diagnosis and management of trophoblastic diseases.     

USA hCG reference service, 10-year report

IntroductionThe USA hCG Reference Service has been dealing with cases of persistent low levels of hCG and gestational trophoblastic diseases for 10 years. Here we present the complete experience.MethodsTotal hCG in serum and urine was measured using the Siemen's Immulite 1000 assay. Hyperglycosylated hCG, nicked hCG, free ß-subunit and ß-core fragment were measured using microtiterplate assays with antibodies B152, B151, FBT11 and B210, respectively.ResultsThe USA hCG Reference Service has identified 83 cases of false-positive hCG, 71 cases of aggressive gestational trophoblastic disease (GTD), 52 cases of minimally invasive GTD, 168 cases of quiescent GTD and 22 cases of placenta site trophoblastic tumor (PSTT). In addition, 103 cases of pituitary hCG have been identified, 60 cases of nontrophoblastic tumor, 4 cases of inherited hCG and 2 cases of Munchausen's syndrome. This is 565 cases total. Multiple new methods are described and tested for diagnosing all of these disorders.ConclusionsThe USA hCG Reference Service experience shows new methods for detecting multiple hCG-related disorders and recommends new approaches for detecting these hCG-related disorders.     

Hyperglycosylated human chorionic gonadotropin (invasive trophoblast antigen) immunoassay: A new basis for gestational Down syndrome screening

BACKGROUND: Serum human chorionic gonadotropin (hCG) and hCG free beta-subunit tests are used in combination with unconjugated estriol and alpha-fetoprotein in the triple screen test, and with the addition of inhibin-A in the quadruple marker test for detecting Down syndrome in the second trimester of pregnancy. These tests have a limited detection rate for Down syndrome: approximately 40% for hCG or free beta-subunit alone, approximately 60% for the triple screen test, and approximately 70% for the quadruple marker test, all at 5%, or a relatively high, false-positive rate. New tests are needed with higher detection and lower false rates. Hyperglycosylated hCG (also known as invasive trophoblast antigen or ITA) is a new test. It specifically detects a unique oligosaccharide variant of hCG associated with Down syndrome pregnancies. We evaluated this new Down syndrome-directed test in prenatal diagnosis. METHODS: Hyperglycosylated hCG was measured in urine samples from women undergoing amniocentesis for advanced maternal age concerns at 14-22 weeks of gestation, 1448 with normal karyotype and 39 with Down syndrome fetuses. RESULTS: The median hyperglycosylated hCG value was 9.5-fold higher in Down syndrome cases (9.5 multiples of the normal karyotype median). The single test detected 80% of Down syndrome cases at a 5% false-positive rate. Urine hyperglycosylated hCG was combined with urine beta-core fragment (urine breakdown product of serum hCG free beta-subunit), serum alpha-fetoprotein, and maternal age-related risk. This urine-serum combination detected 96% of Down syndrome cases at a 5% false-positive rate, 94% of cases at a 3% false-positive rate, and 71% of cases at a 1% false-positive rate. These detection rates exceed those of any previously reported combination of biochemical markers. CONCLUSIONS: Hyperglycosylated hCG is a new base marker for Down syndrome screening in the second trimester of pregnancy. The measurement of hyperglycosylated hCG can fundamentally improve the performance of Down syndrome screening protocols.     

Human choriogonadotropin (hCG): comparisons between determinations of intact hCG, free hCG beta-subunit, and "total" hCG + beta in serum during the first half of high-risk pregnancy.

We have studied the concentrations of intact human choriogonadotropin (hCG) and the free hCG beta-subunit in blood samples from singleton pregnancies at risk for habitual or threatened abortion. The samples were obtained weekly between the 6th and 12th weeks and in the 14th and 16th weeks of gestational age. The concentrations of intact hCG, of the free hCG beta-subunit, and of "total" hCG (i.e., intact hCG and the free hCG beta-subunit: hCG + beta) were measured in serum by specific immunoassays. The distributional statistics (the 5th, 50th, and 95th percentiles) of "total" hCG + beta and of intact hCG showed very similar patterns, whereas the response curves for the free hCG beta-subunit showed very much lower serum concentrations. From these data we also estimated distributional statistics of the percent molar ratios of free hCG beta-subunit to intact hCG. We conclude that (a) the relatively small proportion of free hCG beta-subunit in serum during the first half of singleton pregnancy is far too low to interfere with the applied "total" hCG assay, as compared with the serum values obtained for intact hCG, and (b) the percent molar ratios of free hCG beta-subunit to intact hCG, or to "total" hCG + beta, never exceeded 1.0% throughout the period of pregnancy studied.     

Quantitative, wide-range, 5-minute point-of-care immunoassay for total human chorionic gonadotropin in whole blood

BACKGROUND: Human chorionic gonadotropin (hCG) is among the most common analytes available for point-of-care immunotesting, with most assays currently based on simple manual assay devices. However, as the importance of good analytical performance of rapid assays is increasingly emphasized, more sophisticated immunoassay techniques are needed to meet the future challenges of rapid yet quantitative POC testing. METHODS: We developed a simple, dry-reagent, all-in-one immunoassay for the quantitative measurement of hCG in whole blood, plasma, or serum. The noncompetitive assay equally measures intact, nicked, and hyperglycosylated hCG as well as nonnicked and nicked hCG beta-subunit with a rapid and simple procedure consisting of a 5-min, one-step incubation and, subsequent to washing, the measurement of time-resolved fluorescence directly from a wet well surface. RESULTS: The assay had a detection limit (background + 3 SD) of 0.4 IU/L hCG. The within-run CV was <15% down to 2 IU/L, and the assay was linear to 6000 IU/L. The within- and between-run CVs in heparinized whole blood and plasma were 相似文献   

Are laboratories reporting serum quantitative hCG results correctly?

BACKGROUND: Human chorionic gonadotropin (hCG) is a heterodimeric glycoprotein hormone that exists in multiple forms. Immunoassays commonly used in clinical laboratories measure intact hCG, total beta hCG (intact hCG + hCG free beta-subunit), and/or hCG free beta-subunit. Measurement of serum concentrations of hCG is useful for confirmation and monitoring of pregnancy, diagnosis of trophoblastic diseases and monitoring of the efficacy of treatment, and prenatal screening. Correctly reporting results for the various forms of hCG is clinically important. METHOD: We prepared samples by addition of intact hCG and hCG free beta-subunit to an essentially hCG-free human serum matrix. The samples were analyzed by participant laboratories using various immunoassay methods. RESULTS: We identified errors in participant reporting of intact hCG results as total beta hCG (9.3%; 22 of 235 laboratories) and total beta hCG as intact hCG (13.1%; 8 of 61 laboratories). CONCLUSIONS: Many factors contribute to the erroneous reporting of hCG results, including (a) the complexity of hCG molecule and confusion of nomenclature on the various forms of hCG; (b) laboratory personnel's lack of awareness of the distinctions of the forms of hCG and failure to recognize the specificity of assays for their measurement; (c) lack of clarity and uniformity in manufacturers' reagent labeling; and (d) most product inserts' lack of information on the specificity of each method to the various forms of hCG.     

Charge variants in serum and urine hCG

BACKGROUND: All serum and urine pregnancy tests sold in the United States are calibrated against the WHO 3rd and 4th International Standards (3rd and 4th I.S.) of Human Chorionic Gonadotropin (hCG). These standards have been isolated from pregnancy urine; however, they are used to calibrate, and generate antibodies used in both urine and serum hCG tests. hCG molecules may vary in sialic acid content; this changes the acidity of the molecule. Published studies have shown that these carbohydrate elements may alter recognition of hCG in different serum and urine hCG tests. We investigated the charge variants of hCG in serum and urine samples, and in hCG standards. METHODS: Samples were analyzed by preparative isoelectric focusing. Charge variants of hCG were quantitated using the DPC Immulite hCG assay. RESULTS: A difference was observed in the proportion of charge variants in urine and serum samples. There was a significantly higher proportion of more-acidic variants in the urine samples. CONCLUSIONS: Urine-derived standards may not be representative of serum hCG and therefore may not be appropriate for calibrating serum assays. Variation among hCG test results when using different immunoassays has been a persistent problem for years. Additional studies are needed to focus on the molecular dissimilarity of urine and serum hCG, as well as other factors, to determine their significance and contribution to the problem of interassay variation when comparing hCG results.     

Preparation and characterization of new WHO reference reagents for human chorionic gonadotropin and metabolites

BACKGROUND: The currently used standards for human chorionic gonadotropin (hCG) and its alpha and beta subunits (hCGalpha and hCGbeta) contain substantial amounts of contaminating variants of hCG and other impurities. Furthermore, some partially degraded forms of hCG and its subunits have become of potential clinical importance, e.g., "nicked" forms of hCG (hCGn) and hCGbeta (hCGbetan), which contain cuts in the peptide backbone between amino acids 44-45 or 47-48 in hCGbeta, and a fragment of hCGbeta (hCGbetacf) consisting of amino acids 6-40 and 55-92 bound together by disulfide bridges. The IFCC appointed a working group with the aim of preparing new standards for hCG and related substances to improve standardization of their immunoassays. METHODS: Large amounts of hCG and its subunits as well as of hCGn, hCGbetan, and hCGbetacf were prepared by previously developed purification methods in combination with hydrophobic interaction chromatography and reversed-phase HPLC. Each preparation was characterized on the basis of amino acid and sequence analyses, carbohydrate composition, and electrophoretic patterns. Immunoassays for relevant contaminating proteins were also performed. RESULTS: The major preparations were homogeneous and free of contaminating proteins. Concentrations of the final preparations were determined by amino acid analysis. CONCLUSIONS: Calibrated in substance concentrations (mol/L) based on amino acid analyses, these preparations will facilitate improved standardization of immunoassays for hCG and its metabolites. The six preparations have now been established by the WHO as new 1st Reference Reagents for immunoassays with the following codes: hCG 99/688, hCGbeta 99/650, hCGalpha 99/720, hCGn 99/642, hCGbetan 99/692, and hCGbetacf 99/708. In contrast to the 3rd International Standard (75/537), the clinically most important Reference Reagent for hCG (99/688) contains no hCGn and negligible amounts of free subunits.     

Between-method variation in human chorionic gonadotropin test results

BACKGROUND: Results on sera and calibrators vary 1.4- to 2.3-fold among commercial human chorionic gonadotropin (hCG) assays. The relative contributions of calibrators, standards, hCG charge isoforms, and major structural variants to this variation have not been quantified. METHODS: Purified hCG was separated by isoelectric focusing into four fractions with pI ranges of 3-4, 4-5, 5-6, and 6-7. These four fractions together with pure hCG, hyperglycosylated hCG, hCG beta-subunit (hCGb), nicked hCG, and hCGb core fragment (hCGbcf) were tested in nine commonly used commercial serum assays for hCG. The compositions of pure hCG preparations, standards, and commercial hCG preparations were determined by immunoassay. RESULTS: The three pure hCG preparations and the four hCG charge isoforms each showed parallel responses in the nine commercial hCG assays. Although wide variations were found in the detection of hCG structural variants by the nine assays (range for hyperglycosylated hCG, 468-1544 IU/L; for hCGb, 3187-5535 IU/L; for nicked hCG, 2736-4240 IU/L; and for hCGbcf, <2-130 IU/L), this did not correlate with the between-method variation observed in results for the three pure hCG preparations. Commercial preparations of hCG and calibrators showed great variation in their content of hCG structural variants (from 34% to 100% intact hCG). CONCLUSIONS: Intermethod differences in hCG results were not explained by changes in responses attributable to hCG charge isoforms or to hCG structural variants, but wide variation was observed in concentrations of hCG structural variants in calibrators and in detection of these structural variants. Differences in assay specificity and in composition of the calibrators are the most likely sources of between-method variation.     

Human chorionic gonadotropin in pregnancy diagnostics

Human chorionic gonadotropin (hCG) is a 237 aminoacid glycoprotein hormone composed of two dissimilar α and β subunits noncovalently linked by charge interactions, which are both required for the biological activity of the hormone. Due to structural heterogeneity, hCG exists in biological fluids as a mixture of different isoforms, i.e., intact active hormone (hCG), nicked hCG (hCGn), free β subunits (hCGβ), free α subunit (hCGα), β-core fragment (hCGβcf, predominantly detected in urine and containing amino acids 6-40 and 55-92 linked by disulphide bridges) and nicked free β-subunit (hCGβn). Although the measurement of hCG might be useful in a kaleidoscope of clinical conditions, such as diagnosis, monitoring and follow-up of pregnancy-related disorders, prenatal screening and gynecological cancers, the leading application is still the diagnosis of pregnancy, where it can be measured quantitatively either in serum or urine, in the latter case also using qualitative and rapid immunoassays. Since there is still debate as to whether serum or urine tests are to be preferred for establishing a diagnosis of pregnancy, we discuss here the main analytical and clinical aspects of hCG measurement for the diagnosis of pregnancy, highlighting the advantages and limitations of assessing hCG in urine and serum.     

Heterophilic antibodies: a problem for all immunoassays

We verified that antibody-binding substances in serum that interfere in two-site immunoassays involving murine antibodies are heterophilic antibodies. Incubation of serum containing heterophilic antibodies and a murine monoclonal antibody to human choriogonadotropin (hCG) leads to formation of a series of soluble immune complexes. We investigated the recognition of hCG by reagent antibody in the presence of heterophilic antibodies and found this recognition to be diminished. Consequently, about 30% of serum samples containing heterophilic antibodies falsely appear to contain increased concentrations of hCG. The effect on analyte recognition probably results from steric inhibition of hCG binding to complexed antibody. Heterophilic antibodies detected with a murine antibody also bound immunoglobulin from several other species but did not bind all of those tested.     

Free alpha-subunit, free beta-subunit of human chorionic gonadotropin (hCG), and intact hCG in sera of healthy individuals and testicular cancer patients.

To determine the serum concentrations of human chorionic gonadotropin (hCG), its free beta-subunit (hCG beta), and the free alpha-subunit (free alpha) common to all human glycoprotein hormones under physiological and pathological conditions, we developed monoclonal antibody-based immunoenzymometric assays. Free alpha-subunit was detected in the sera of all healthy individuals of both sexes; hCG was measurable in sera of 54% of the men, and 46% were positive for free hCG beta; in nonpregnant women, 69.5% were positive for hCG, 68.4% for the free beta-subunit. Pathological conditions, i.e., hCG-producing tumors, were studied in vitro and in vivo. In vitro, the concentrations of hCG, free hCG beta, and free alpha in tissue-culture supernates of a choriocarcinoma cell-line ("JAR") showed a parallel pattern during time-course analysis. In vivo, in long-term follow-up studies of 13 patients with testicular cancer, serum concentrations of the three analytes paralleled each other, whether the disease was in remission or not. Because of a selective increase of free hCG beta and free alpha in 27% of seminomatous tumor patients and in 13% of the nonseminomatous patients, the percentage of tumor-marker-positive sera was increased from 15% to 42% and 57% to 70%, respectively, by the additional measurement of free hCG beta and free alpha. Thus hCG, free hCG beta, and free alpha are physiologically present in a high percentage of the sera from healthy men, and the determination of free hCG beta and free alpha, although not of prognostic value, improves the diagnostic possibilities in patients with testicular cancer.     

Development and validation of a choriogonadotropin beta-subunit radioimmunoassay for serum choriogonadotropin using commercially available components

A sensitive, specific, accurate and precise radioimmunoassay procedure developed for the beta-subunit of serum choriogonadotropin (hCGbeta) is described. 1. The assay employs an anti-hCGbeta (rabbit) serum generated against hCGbeta, highly purified intact choriogonadotropin (hCG) as standard, and [125I]hCG as the radioactive ligand. The antibody-bound hCG was separated from the free hormone by the addition of goat anti-rabbit gamma-globulin. 2. The detection limit of the assay was approximately 75 microIU hCG which corresponds to a serum concentration of approximately 0.75 mIU/mL. 3. Cross reactivity studies performed with human luteinizing hormone (hLH) and human thyroid-stimulating hormone (hTSH) indicated minimal interferences from these structurally similar glycoproteins. Parallel dose-response curves were demonstrated between dilutions of sera with elevated hCG concentrations and the standard reference preparation. A non-specific binding of less than 2.5% of the total [125I]hCG was routinely observed. 4. The analytical recovery of hCG added to human sera varied from 94 to 110%, with a mean recovery of 101%. 5. The inter-assay variation was determined by assaying (n=30) 3 different quality control pools. The following data were obtained: X1=4.6 +/- 0.5 mIU/mL (CV=10.9%); X2=8.1 +/- 0.9 mIU/mL (CV=11.1%); and X3=36.8 +/- 2.8 mIU/mL (CV=7.6%). 6. The clinical data collected from subjects with trophoblastic disease agreed with previously published studies. All of the reagents are available commercially.     

Outcome validation of the Beckman Coulter access analyzer in a second-trimester Down syndrome serum screening application

BACKGROUND: Mid-trimester maternal serum alpha-fetoprotein (AFP) and unconjugated estriol (uE3) are 30% lower and human chorionic gonadotropin (hCG) is twofold higher in Down syndrome pregnancies compared with unaffected pregnancies. In maternal serum screening, patient-specific risks are calculated using published gaussian frequency distribution parameters for these three markers obtained with previously available immunoassays. New immunoassays must generate similar distribution parameters if the accuracy of assigned risks and overall performance of prenatal screening are to be maintained. METHODS: Agreement between the Beckman Coulter Access and the Bayer Immuno 1 assays for AFP and hCG and the Amersham Amerlex-M RIA for uE3 was assessed in 558 fresh sera. Precision was measured over 6 weeks. Median concentrations were calculated by regression of 568 Caucasian singleton pregnancy samples against gestational age in days. Frozen mid-trimester sera from 44 confirmed Down syndrome singleton pregnancies (cases) were selected without conscious bias for reanalysis, and each case was matched with five control specimens from unaffected pregnancies. Serum markers were expressed as the multiple of the median (MoM) concentration derived from the control samples, corrected for maternal weight and converted to their log-equivalent values. Normality was assessed using probability plots and the Shapiro-Wilk W-test. Gaussian distribution parameters were compared with established values, and Down syndrome risk calculations were assessed with a commonly used risk algorithm. RESULTS: The Access AFP and hCG assays had consistent proportional agreement with the established assays, whereas agreement between the uE3 methods was less consistent. Analytical imprecision was 3-6% at mid-trimester concentrations. Normal distributions were obtained for the log MoM values of all three markers in both the Down syndrome and unaffected populations, and their gaussian distribution parameters compared well with established values. The performance of the Access assays in an established trivariate risk algorithm for Down syndrome was equal to the performance exhibited by traditional methods. CONCLUSION: The Beckman Coulter Access analyzer provides valid mid-trimester serum AFP, uE3, and hCG results and risk assessments when applied in a prenatal Down syndrome screening service.     

Comparison of two assays measuring human chorionic gonadotrophin serum concentrations in pregnancy termination and trophoblastic or non-trophoblastic tumours

Background: Differences in human chorionic gonadotrophin (hCG) results provided by the commercial immunoassays reflect the heterogeneity of antibodies and the use of suboptimal standards. As a consequence, the principal forms of hCG and metabolites are differentially detected and the hCG tests are not suited for the same clinical applications. Conflicting results are available in the literature regarding which hCG variants are recognized by the Roche Elecsys hCG?+?β test. The aim of our study was to compare the hCG concentrations provided by the Siemens Immulite 2000 test and the Roche test as well as to assess the concordance between both assays.

Methods: In this purpose, 152 samples obtained from women and 44 samples from men were analysed by both tests during the follow-up of pregnancy termination, gestational trophoblastic disease and malignancies. The intermediate precision of the Roche test was also investigated on a pool with a low hCG concentration.

Results and conclusions: The hCG concentrations measured with the Roche test were slightly lower compared with the Siemens assay; mean biases of ?34.2% and ?8% were respectively obtained for hCG values ≤100?UI/L and higher than 100?UI/L. The overall agreement between both assays was 96.1% for women and 97.7% for men. By using an upper reference limit of 3.2?UI/L for women and 1.6 UI/L for men, the Roche test demonstrated a respective concordance of 98.7% and 100%. This test also yielded an excellent precision with a coefficient of variation of 2.8% at a mean hCG concentration of 7?UI/L.     

Importance of the detection method for intact dimeric human chorionic gonadotropin without interference with the free human chorionic gonadotropin beta subunit for pregnancy exclusion before liver transplantation in a woman with cholangiocarcinoma.

Assay of human chorionic gonadotropin (hCG) is mainly used for the detection and monitoring of pregnancy, and for the follow-up of trophoblastic tumors. The serum free beta-hCG subunit (hCGbeta) is also a tumor marker in many non-trophoblastic tumors, including gastrointestinal cancers. In this work, we compared the performance of several immunoassays for pregnancy exclusion before liver transplantation and in the follow-up of a woman with cholangiocarcinoma. Serum hCG was detected with the Abbott Testpack plus hCG-Combo and measured with four automated sandwich immunoassays: ADVIA-Centaur, ACS:180, AxSYM and Dimension. hCGbeta was determined by an automated fluorescence sandwich immunoassay (Kryptor-Free beta hCG) and with a specific immunoradiometric assay (ELSA-F beta hCG, Schering). The expression of hCG was also evaluated by immunohistochemistry on sections of intrahepatic cholangiocarcinoma cells and on peritoneal metastases. Before transplantation, discordant results were observed for pregnancy exclusion. Qualitative Testpack and Dimension tests detected no hCG-like immunoreactivity, whereas the ADVIA-Centaur, ACS:180 and AxSYM tests revealed positive levels. The same discrepancy was obtained in follow-up of the patient after liver transplantation. hCGbeta assay and immunohistochemical staining revealed tumor cell secretion of hCGbeta. In conclusion, a specific serum immunoassay for intact dimeric hCG without cross-reaction with hCGbeta should be adopted as routine policy for pregnancy exclusion before liver transplantation.     

Total hCG tests

IntroductionThere are 12 types of automated total hCG tests sold today, the Abbott Architect, Abbott AxSym, the Beckman Access 2. Beckman DxI 800, the Ortho Vitros EciQ, Roche Elecsys hCG + β, Siemens ACS180, Siemens Centaur, Siemens Dimension, Siemens Immulite and Siemens Stratus, and the Tosoh A1A. All tests claim to be total hCG tests but do not define what total means. Total hCG test needs to detect all hCG variants in order to be used for all hCG test clinical applications. Here we assess this ability.MethodsCoded samples of pure hCG, nicked hCG, hyperglycosylated hCG, nicked hCG missing C-terminal peptide, nicked hyperglycosylated hCG, asialo hCG, hCGβ, nicked hCGβ and β-core fragment were tested blindly in serum and urine at 10 independent laboratories.ResultsWhile the Siemens Immulite total hCG test detected 8 of 9 hCG variant standards, other assays poorly detected important determinants such as nicked hCG missing the C-terminal peptide, β-core fragment, hyperglycosylated hCG, nicked hCG, asialo hCG, and hCGβ. Four assay appropriately detected 4 of 9 variants, 2 assays detected 3 of 9, 4 assays detected 2 of 9 and 1 assay only appropriately detected 1 of 7 hCG variants.DiscussionCare is needed in selecting a total hCG test. The Siemens Immulite tests performed best at detecting all the hCG variants making it appropriate for all applications. Nine assays had limited applications, 3 of the assays were appropriate for advanced pregnancy testing only.     

Advances in the clinical laboratory detection of gestational trophoblastic disease

BACKGROUND: Gestational trophoblastic disease (GTD) consists of a spectrum of disorders that are characterized by an abnormal proliferation of trophoblastic tissue. Gestational trophoblastic neoplasia (GTN) refers to a subset of GTD with a persistently elevated serum hCG in the absence of a normal pregnancy and with a history of normal or abnormal pregnancy. Although previously a lethal disease, GTN is considered today the most curable gynecologic cancer. However, a delay in the diagnosis may increase the patient's risk of developing malignant GTN, and therefore the prompt identification of GTN is important. SERUM MARKERS: hCG test is essential for detection of GTN. It has emerged that there are problems with hCG tests. In addition to regular hCG, at least five major variants of hCG are present in serum samples. False-positive hCG (phantom hCG) can occur in the absence of GTN. Low-level real hCG may occasionally persist in the absence of clinical evidence of pregnancy or GTD. Alternatively, low-level real hCG may be due to pituitary hCG. Other placental hormones, human placental lactogen (hPL), inhibin and activin, and progesterone have also been evaluated as tumor markers for GTD. CONCLUSION: hCG has high diagnostic sensitivity, approaching 100% sensitivity, for managing the treatment of GTN and for detecting recurrences of disease. It is recommended to use hCG test that recognizes all forms of the hCG molecule. In cases where low-level hCG persists, it must be differentiated whether it is real or false. Real-hCG may be due to quiescent gestational trophoblastic disease or pituitary hCG. It has not yet been established whether measurement of markers other than hCG (hPL, inhibin, activin, and progesterone) is useful in the detection and follow-up of GTD.