False-positive hCG Research Articles

1. Persistent elevation of BHCG-levels in a patient with stage 5D Chronic Kidney Disease

Introduction and aim: A 24 year old female with Stage 5D chronic kidney disease (CKD) presents with persistent positive BHCG levels. BHCG elevation causes include pregnancy, pituitary production, hydatidiform mole, persistent trophoblast disease, malignancies and false positive hCG. Variants of the hCG molecule has been identified and includes sulfated hCG, hyperglycosylated hCG, hCG free β-subunit and hyperglycosylated hCG free β-subunit. Different hCG fractions are generated depending on the disease process. Isolated cases of falsely raised BHCG in both men and women with CKD have been reported. Origin of hCG has been attributed to pituitary production, coupled with CKD impairing metabolism and clearance of hCG.Methodology: Samples were tested by the NHLS Universitas Academic Laboratory using the Cobas e 601 analyzer (Roche) for intact human chorionic gonadotropin and the β-subunit. This immunoassay detects the holo-hormone, nicked forms of hCG, β-core fragment and free β-subunit. A qualitative urine test, detecting total hCG was negative, while a laboratory urine analysis had a positive result. Analysis on different instruments and serial dilutions excluded assay interference from human antimouse antibodies (HAMA), heterophilic antibodies or a high dose hook effect. Imaging studies including magnetic resonance imaging (MRI) brain, pelvis, computed tomography (CT) chest and pelvic ultra sound was performed. Diagnostic laparoscopy was refused by the patient due to her ongoing peritoneal dialysis.Results: Serial BHCG results show persistent elevation. Imaging studies yielded no explanation to HCG production.Conclusion: Elevated BHCG could be attributed to a tumour of gestational or non-gestational origin, failed pregnancy, familial elevated hCG, reduced clearance and degradation of hCG in CKD or changes of hCG associated with CKD. Immunoassay interference should be considered when patient results and clinical presentation differs. False positive test results may subject patients to unnecessary investigation and it may prevent patients from qualifying for organ transplantation.

Evaluation of Leukocyte and Bacterial Interference in Point-of-Care Human Chorionic Gonadotropin Tests

We read with interest the Letter to the Editor by Jao et al. [1] which reported false positive results using the point-of-care (POC) One Step Pregnancy Test device (ACON Laboratories Inc., San Diego, CA, USA). The authors determined that false positive results occurred when the concentration of white blood cells (WBCs) in a urine specimen exceeded 0.4×109 cells/L. We recently observed several false-positive human chorionic gonadotropin (hCG) results using the POC hCG Combo Rapid Test (Cardinal Health, Waukegan, IL, USA). We observed that most of our false positive specimens were in patients with evidence of urinary tract infection (UTI) and pyuria; with this information, and in the context of the findings by Jao et al. [1] that WBCs may result in false positive hCG assays, we evaluated the effect of WBCs or bacteria in urine on the analytical performance characteristics of both devices. Two buffy coat preparations were created using pooled whole blood from 25 patients. The buffy coat preparations were analyzed using the Coulter LH 750 Hematology Analyzer (Beckman Coulter, Brea, CA, USA) to assess the purity of the preparation. WBCs were prepared on two separate occasions and the total WBC counts of the pools were 57.5×109/L and 200×109/L. These WBC preparations were then diluted into urine from a male patient at six different WBC concentrations (0.1×109, 0.4×109, 1.0×109, 5.0×109, 10.0×109, and 21.0×109/L) including and exceeding the concentration used by Jao et al. [1]. The urine was then tested on both the hCG One Step and the hCG Combo Rapid test according to the manufactures' recommendations. All specimens were negative on both devices. The explanation for the different results observed in the study by Jao et al. [1] and the current study are unclear. Jao et al. [1] do not describe the source of their WBC preparation, it is unknown if it is from one patient or multiple patients, and the WBC differential is also unknown. It is possible that differences in these parameters could explain the discrepancy. With the knowledge that most of our patients with false positive results had evidence of UTI, and knowing that Escherichia coli is the most common cause of UTI in the outpatient setting, we wondered if E. coli specifically might account for the false positive results. To test this hypothesis, we made logarithmic dilutions (107 colony forming units [CFU]/mL, 106 CFU/mL and 105 CFU/mL) of a clinical isolate of uropathogenic E. coli into sterile urine from a male patient and tested these samples on both devices; all tests yielded negative results. To account for the fact that addition of E. coli and/or WBCs to sterile urine might not accurately replicate the matrix of a clinical specimen from a patient with UTI, we then tested 10 urine specimens from unique, female patients that were culture positive for E. coli (>50,000 colonies/mL) and 5 additional urine specimens that were submitted from outpatients to the microbiology laboratory for culture for presumed UTI. All of these specimens, when tested with the hCG Combo Rapid Test, also gave negative results. A recent study by Snyder et al. [2] reported that high WBC concentrations resulted in falsely increased serum hCG concentrations using the Beckman Coulter Access Total βhCG on the UniCel DxI (Beckman Coulter, Chaska, MN, USA). According to the authors, the false positive results may be attributed to leukocyte alkaline phosphatase reacting with the conjugate that is used in those immunoassays. However, both POC devices used in this particular study use colloidal gold as the color conjugate, hence leukocyte alkaline phosphatase should not result in this specific interference. Based on the information in this study, we feel there is inadequate evidence at this time to conclude that false-positive hCG results, in either the One Step Pregnancy Test device or the hCG Combo Rapid Test, can be attributed to elevated WBC concentrations in the urine. However, we continue to see false positive results that suggest the presence of a yet unidentified interfering substance.

USA hCG reference service, 10-year report

Introduction The 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. Methods Total 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. Results The 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. Conclusions The USA hCG Reference Service experience shows new methods for detecting multiple hCG-related disorders and recommends new approaches for detecting these hCG-related disorders.

The need for a quantitative urine hCG assay

Background The USA uniquely does not use quantitative urine human chorionic gonadotropin (hCG) tests despite being invaluable in pregnancy testing and in monitoring cancer patients. We look at current hCG tests and their detection of the degraded forms of hCG predominant in urine. We examine levels of urinary hCG, its usefulness in pregnancy testing, and advantages of urine testing in false positive hCG cases and cancer cases. Methods hCG assays were blindly evaluated at 10 laboratories running different methodologies. Daily urine samples from 164 women were collected through 5 menstrual cycles or until pregnancy was achieved. Urines were assayed for total hCG. We also examined the use of quantitative urine hCG in confirming false positive serum hCG results in 80 clinical cases. Results Only the Siemens Immulite test was shown to detect the degraded forms of hCG present in urine. This test equally recognized urine and serum hCG. We investigated background hCG in 9026 urines, the mean hCG level was 0.04 IU/L, and the 99th centile was 1.4 IU/L. In cycles where pregnancy was achieved, hCG could be detected in urine at 24.6 days of a 28.7 day menstrual cycle. At this time, the average hCG was 6.02 IU/L, setting a sensitivity level for quantitative urine hCG tests to detect pregnancy. Quantitative urinary hCG proved critical in detecting cancer in 3 of 80 cases complicated by false positive serum hCG. Conclusions The need for a quantitative urine hCG assay is undeniable and we invite manufacturers to produce a quantitative urine hCG test.

False-Positive Serum Human Chorionic Gonadotropin (hCG) in a Male Patient with a Malignant Germ Cell Tumor of the Testis: A Case Report and Review of the Literature

A 39-year-old male patient with a favorable prognosis stage IIB metastatic malignant germ cell tumor (GCT) and elevated pre- and postorchiectomy serum human chorionic gonadotropin (hCG) was treated with three courses of combination chemotherapy resulting in a rapid normalization of his serum hCG. Within 2 months after the cessation of chemotherapy, his serum hCG increased again, suggesting tumor recurrence. Pathological examination of the resected residual retroperitoneal lymph nodes revealed no vital tumor cells. Based on the further rise in his serum hCG and enlargement of mediastinal lymph nodes on computed tomography scan, the patient underwent second- and third-line chemotherapy, which did not result in normalization of his serum hCG. Reanalysis of stored serum samples with other immunoassays revealed that the elevated serum hCG levels collected before first-line chemotherapy were indeed elevated, but those collected after first-line chemotherapy were all falsely positive. Currently, the patient is still alive and disease free. This is the first report of a male cancer patient who received unneeded second- and third-line chemotherapy for relapse based on false-positive hCG results. We discuss the pitfalls of false-positive serum hCG measurements, including heterophilic antibodies, as in our IgA-deficient patient, and review the literature.

Persistent Low Concentration of Human Chorionic Gonadotropin in a Nonpregnant Woman

A 48-year-old woman presented for radio-iodine ablation therapy 3 months after undergoing a complete thyroidectomy performed for compressive goiter symptoms. The patient’s medical history included stage-3 follicular variant papillary thyroid cancer with no nodal involvement and no metastatic disease. A 6.5-cm papillary carcinoma had been identified and removed surgically. Despite this surgical treatment, 3 foci were detected by 125I uptake testing, a finding that prompted the use of therapeutic ablation. Because the patient reported 5 months of amenorrhea, a quantitative serum human chorionic gonadotropin (hCG) test (hCG+β assay, Roche Diagnostics) was performed to rule out pregnancy. The result was 7.0 IU/L (reference interval: <5.0) and the administration of 100 mCi I131 was cancelled owing to concern for a potential pregnancy. A repeat hCG test performed 4 days later was 7.0 IU/L. Follicle stimulating hormone (FSH) was determined to be 110 IU/L [reference intervals: 1.9–11.6 (follicular phase), 1.4–9.6 (luteal phase), and 21.5–131 IU/L (postmenopausal)]. hCG is produced by the trophoblastic tissue of the placenta and hence is a reliable marker for pregnancy. hCG also has clinical utility as a tumor marker because of its production by trophoblastic and nontrophoblastic neoplasms. Finally, hCG is also produced by the gonadotropic cells of the pituitary during the menopause (1)(2). As demonstrated by this patient, a persistent low concentration of hCG is particularly perplexing. Such cases have 3 potential etiologies: (a) false-positive hCG due to interfering antibodies, (b) quiescent gestational trophoblastic disease, and (c) pituitary hCG. ### false-positive hCG due to interfering antibodies There are several reports of falsely increased hCG due to endogenously produced interfering antibodies (3). Interfering antibodies can be of 2 types: human antianimal antibodies (HAAA) or heterophile antibodies. HAAAs are directed toward a specific antigen and may be produced after treatment with therapeutic antibodies or exposure to animal antigens (4). Heterophile antibodies display …

Elevated hCG Outside of Pregnancy—Diagnostic Considerations and Laboratory Evaluation

Human chorionic gonadotropin (hCG) is a glycoprotein hormone produced by trophoblastic tissues, and its identification is frequently relied upon to establish the diagnosis of pregnancy. Entities other than pregnancy, such as false-positive hCG results, pituitary hCG, exogenous hCG, and both trophoblastic and nontrophoblastic neoplasias, can also cause laboratory assays for hCG to show positive results. Because of their rarity, these conditions are not commonly recognized, and the steps to differentiate between them are not widely known. Discriminating between the causes of elevated hCG in nonpregnant patients can be confusing. An understanding of the differential diagnosis and awareness of available diagnostic modalities are essential for accurate diagnosis and avoidance of potentially harmful treatments. Obstetricians & Gynecologists, Family Physicians. After completion of this article, the reader should be able to state the importance of types of human chorionic gonadotropin (hCG), recall their presence in both trophoblastic and nontrophoblastic neoplasias, and explain how important it is to distinguish between the various causes of an elevated serum hCG to avoid harmful treatments.

Gestational trophoblastic diseases: 4. Presentation with persistent low positive human chorionic gonadotropin test results

Objectives. A high proportion of women with persistent low levels of hCG, in the absence of pregnancy or any evidence of tumor, have received chemotherapy and hysterectomy for assumed malignancy. Such chemotherapy and surgery were ineffective and unwarranted. This study identifies the causes of persistent low level of hCG and provides guidelines for the management of these patients, preventing unnecessary treatment in the future. Methods. The USA hCG Reference Service has consulted on 170 women with low levels of hCG persisting for 3 months or longer. Serum total hCG was measured in the Diagnostic Products Corporation (DPC) Immulite assay and hyperglycosylated hCG in the Nichols Advantage test. Results. Among these 170 patients, the average persistent hCG result was 102 ± 152 mIU/ml, with a range of 6.1–900 mIU/ml. Thirteen (7.6%) of the 170 patients had true malignancy, 5 had placental site trophoblastic tumor, 3 had other gestational trophoblastic neoplasms (GTN), and 5 had non-trophoblastic malignancies. The remaining 157 patients had false-positive hCG, quiescent gestational trophoblastic disease (quiescent GTD), or pituitary hCG (hCG of pituitary origin). Of 71 patients with false-positive hCG, 47 patients received chemotherapy and 9 had surgery that had no effect on the level of hCG. Five of these patients with false-positive hCG were being monitored for hydatidiform mole or GTN. The majority of these cases were first investigated following an incidental pregnancy test. Of 69 patients who had quiescent GTD, 41 received chemotherapy and 9 underwent hysterectomy. All these therapies were unnecessary and ineffective. While 21 patients with quiescent GTD followed incidental pregnancy tests, the majority were discovered while monitoring patients after treatment for hydatidiform mole or GTN/choriocarcinoma ( n = 48). Seventeen cases of pituitary hCG were found among those women who were peri- or post-menopause. Two patients also received chemotherapy for assumed malignancy which was not present. Conclusion. Clinicians frequently assume that an elevated hCG implies that a patient is pregnant or has GTD or recurrent GTN, even when apart from the pregnancy test, no clinical evidence was found to support such a diagnosis. In most of these cases of persistent low hCG etiologies, all therapies were found unnecessary and ineffective. Guidelines are proposed for managing these patients. It is essential to demonstrate a malignancy clinically and with readily available biochemical tests before initiating therapy. This applies whether the patient is identified by an incidental pregnancy test or is actively being monitored for gestational trophoblastic disease.

Easy fix for clinical laboratories for the false-positive defect with the Abbott AxSym total β-hCG test

Background: False-positive hCG results can lead to erroneous diagnoses and needless chemotherapy and surgery. In the last 2 years, eight publications described cases involving false-positive hCG tests; all eight involved the AxSym test. We investigated the source of this abundance of cases and a simple fix that may be used by clinical laboratories. Methods: False-positive hCG was primarily identified by absence of hCG in urine and varying or negative hCG results in alternative tests. Seventeen false-positive serum samples in the AxSym test were evaluated undiluted and at twofold dilution with diluent containing excess goat serum or immunoglobulin. Results: We identified 58 patients with false-positive hCG, 47 of 58 due to the Abbott AxSym total hCGβ test (81%). Sixteen of 17 of these “false-positive” results (mean 100 mIU/ml) became undetectable when tested again after twofold dilution. Conclusions: A simple twofold dilution with this diluent containing excess goat serum or immunoglobulin completely protected 16 of 17 samples from patients having false-positive results. It is recommended that laboratories using this test use twofold dilution as a minimum to prevent false-positive results.

Persistent low levels of human chorionic gonadotropin: A premalignant gestational trophoblastic disease

Objective: This study was undertaken to evaluate the significance of persistent low-level human chorionic gonadotropin (hCG) titers (usually <50 IU/L) in the absence of clinical evidence of pregnancy or gestational trophoblastic disease. Study Design: The USA hCG Reference Service consulted on 114 cases with persistent low levels of hCG; 51 had false-positive hCG results. The remaining 63 cases had real hCG results and are presented here. Results: Antecedent gestational events included hydatidiform mole (27), pregnancy (35), and gestational trophoblastic neoplasm (1). Forty of the 63 (64%) cases received therapy, including chemotherapy (38), hysterectomy (2), or both (10). Despite treatment, in all cases, low hCG titers persisted. After 1 to 4.5 years of low titers, four women had a sudden rapid increase in hCG levels, and malignant disease was confirmed or clearly suggested (gestational trophoblastic neoplasm [3] and placental site trophoblastic tumor [1]). Invasive trophoblast antigen (ITA) is a marker of invasive cytotrophoblast cells. ITA was measured in 38 of the cases with persistent low hCG, in all cases ITA accounted for less than 25% of the hCG concentration. It was also determined in the 4 cases indicated with malignant disease, accounting for more than 80% of the hCG. Conclusion: The presence of persistent low-level hCG titers defines a subset of women with preinvasive or quiescent gestational trophoblastic disease. ITA effectively detected the presence or absence of invasive cells in these cases. The recommended management of the quiescent disease is close surveillance without therapy until malignant disease detected. (Am J Obstet Gynecol 2003;188:1254-9.)

ACOG Committee Opinion No. 278: Avoiding Inappropriate Clinical Decisions Based on False-Positive Human Chorionic Gonadotropin Test Results

Clinically significant false-positive human chorionic gonadotropin (hCG) test results are rare. However, some individuals have circulating factors in their serum (eg, heterophilic antibodies or nonactive forms of hCG) that interact with the hCG antibody and cause unusual or unexpected test results. False-positive and false-negative test results can occur with any specimen, and caution should be exercised when clinical findings and laboratory results are discordant. Methods to rule out the presence of interfering substances include using a urine test, rerunning the assay with serial dilutions of serum, preabsorbing serum, and using another assay. Physicians must decide whether the risks of waiting for confirmation of results outweigh the risks of failing to take immediate medical action. Patients should be notified if they are at risk for recurrent false-positive hCG test results, and this information should be included in the patient's medical record.

Use of Heterophilic Antibody Blocking Agent (HBT) in Reducing False-Positive hCG Results

The USA hCG Reference Service aids physicians in the interpretation of discordant or irregular human chorionic gonadotropin (hCG) results that do not concur with physical findings. The Service has now observed 24 cases of false-positive hCG results (14–571 IU/L). All have been cases erroneously diagnosed with choriocarcinoma or gestational trophoblast disease without demonstrable pregnancy or tumor (1)(2)(3)(4). Because of false-positive hCG results, patients have needlessly received chemotherapy, hysterectomy, and/or other surgery. The suspected cause for serum false-positive hCG is the presence of heterophilic antibodies that bind both capture and detection antibodies, effectively bridging them in the same way as the target antigen should in a standard ELISA format. Until recently, …

Utility of Commonly Used Commercial Human Chorionic Gonadotropin Immunoassays in the Diagnosis and Management of Trophoblastic Diseases

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. 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. 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). 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.

False diagnosis and needless therapy of presumed malignant disease in women with false-positive human chorionic gonadotropin concentrations

12 women were diagnosed of having postgestational choriocarcinoma on the basis of persistently positive human chorionic gonadotropin (hCG) test results in the absence of pregnancy. Most of the women had extirpative surgery or chemotherapy, or both, without significant diminution in hCG titre. Our aim was to assess whether the hCG concentrations were false-positive test results. Samples were tested for hCG, hCG free beta subunit, and hCG beta-core fragment. Assay kinetics were also assessed, and samples were tested independently by competitive RIA. False-positive hCG concentrations were identified by two criteria: detection of hCG in serum and lack of detection of hCG and its degradation products in urine; and wide variations in results for different hCG assays. We corroborated false-positive hCG values by the lack of parallel changes in hCG results when serum was diluted, by false detection of other antigens, and by failure to detect hCG with in-house assays. All 12 women met both criteria for false-positive hCG, and all had corroborating findings. In all 12 cases, a false diagnosis had been made, and most of the women had been subjected to needless surgery or chemotherapy. Assay kinetics indicated that heterophilic antibodies were responsible for the false-positive results. As a result of our findings all further therapy was stopped. Current protocols for the diagnosis and treatment of choriocarcinoma should be modified to include a compulsory test for hCG in urine.

False-Positive hCG Assay Results Leading to Unnecessary Surgery and Chemotherapy and Needless Occurrences of Diabetes and Coma

Much concern has been raised by the unraveling at the hCG Reference Service of six cases of persistent phantom human chorionic gonadotropin (hCG). These are false-positive hCG results, which are likely attributable to human anti-mouse IgG or to heterophilic antibodies (1)(2)(3). The hCG Reference Service, started in January 1998 to aid with the interpretation of irregular or discordant hCG immunoassay results, requests parallel serum and urine samples. Each is tested in four separate two-step microtiter plate ELISAs (assay 1 detects intact hCG, assay 2 detects nonnicked or bioactive hCG only, assay 3 detects the hCG free β-subunit only, and assay 4 detects the hCG β-core fragment only) at three different concentrations (undiluted, a 1:2 dilution, and a 1:5 dilution). From the data, inferences are made about the nature (nonnicked or nicked hCG, free β-subunit, and β-core fragment) and likely source (trophoblast disease, pituitary hCG, cancer, or phantom hCG) of the hCG immunoreactivity. …

Pseudocyesis and its modern perspective.

EDITORIAL COMMENT: We accepted this paper for publication because we have not reported previously on pseudocyesis, which is a rare condition, especially if ‘first trimester cases’ are excluded where there has been confusion with interpretation of intervals of amenorrhoea. These cases can occur at the climacteric when elevated levels of LH can give a false positive HCG test result with older methods of assay and add further to the temporary clinical confusion. The classical clinical picture, unlike the 3 cases reported in this paper, is said to be the nullipara approaching the time of the climacteric who is anxious to conceive. Queen Mary's case must be the most famous on record and also the best documented by means of the serial bulletins issued for her loyal subjects concerning the progress of her royal pregnancy (A). The editor can remember only 1 case of ‘late pregnancy’ pseudocyesis in 40 years of obstetric practice. This woman was finally convinced of her nonpregnant status by failure of a fetal skeleton to show on an abdominal X‐ray. This was many years ago. This test was claimed to be definitive. One wonders how these women coped thereafter. We agree with the authors that follow‐up, not necessarily by a psychiatrist, is important. In the editor's experience pseudocyesis of late pregnancy is less common than advanced true normal pregnancy in a nullipara aged more than 40 years, married for many years, who presents with abdominal pain and finds out to her delighted surprise that she is in labour at term and shortly thereafter produces a surviving normal infant. The reviewers of this paper did not agree with the suggestion that curettage would be an appropriate procedure to convince a woman with pseudocyesis that she was not pregnant. However, the authors, having read this editorial comment, stated that curettage is mentioned in the pseudocyesis literature (4).(A) Dewhurst J. Royal Confinements. Weidenfeld and Nicolson, London. 1980; 28–29.

False-positive hCG by enzyme immunoassay resulting in repeated chemotherapy

In abnormal pregnancies, it is necessary to follow hCG levels to ensure resolution of the pregnancy, either spontaneously or after therapy. Lack of a normal resolution can be treated with methotrexate. A 32-year-old woman had a persistently elevated serum hCG level analyzed by enzyme immunoassay technique before and after being treated with three courses of methotrexate. Analysis of the serum samples by radioimmunoassay technique gave negative results. If the expected laboratory response is not forthcoming in the treatment of an abnormal pregnancy with methotrexate, hCG analysis by another assay method is recommended. False-positive hCG levels can result from the presence of heteroantibodies in the serum of the patient.