FERTILITY AND STERILITY

VoL 58, No.3, September 1992

Printed on acid-free paper in US.A.

Copyright © 1992 The American Fertility Society

An office semiquantitative serum human chorionic gonadotropin determination

Sjarlot Kooi, M.D. Hans C. L. V. Kock, M.D. * Department of Gynecology and Obstetrics, Maria Hospital, Tilburg, The Netherlands

Objective: To compare the human chorionic gonadotropin (hCG) concentration, established by a standard serum quantitative hCG fluorescent immunoassay and a semiquantitative serum determination. Design: Patients were asked to give two serum samples early in pregnancy to establish the accuracy of a semiquantitative serum hCG test in diluted and undiluted serum samples. Setting: In a laboratory setting, two serum samples were determined; one sample was submitted for standard serum hCG radioimmunoassay, and the other was tested for hCG by the 25 IU Tandem ICON Assay (Hybritech, Liege, Belgium) in diluted and undiluted serum samples. Participants: Sixteen patients supposed to be pregnant. Main Outcome Measures: Within dilutional zones, the results of a semiquantitative hCG test were compared with a known standard quantitative serum hCG immunoassay measurements. Result: The semiquantitative hCG ranges of serum hCG compare fairly well with an accurate standard quantitative serum hCG immunoassay. Conclusion: The determination of a serum hCG range compares well with the standard quantitative serum hCG immunoassay (First International Reference Preparation) and can be completed within 15 minutes. This office semiquantitative serum hCG determination proved to be a quick and reliable test. Fertil Steril 1992;58:522-5 Key Words: Human chorionic gonadotropin subunits, quantitative hCG immunoassay, serum serial hCG dilutions

Human chorionic gonadotropin (hCG) is a glycoprotein with an alpha- and a beta-subunit. The intact dimer hCG is the biologically active hormone, and the beta-subunit determines its specificity (13). Cunningham (4) cites Hirose with the first demonstration in 1919 of the trophic effect of human placental tissue fragments on the ovaries and uterus of the rabbit. Cunningham (4) refers also to Ascheim and Zondek who demonstrated a pregnancy hormone (prolan) in the urine of pregnant women that formed the basis for the A-Z pregnancy test. Immunological pregnancy tests were first developed in

Received September 16, 1991; revised and accepted May 19, 1992. * Reprint requests: Hans C. L. V. Kock, M.D., Department of Gynecology and Obstetrics, Maria Hospital, Tilburg, The Netherlands.

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1960 (5). Vaitukaitis and Ross (6) were the first to describe a radioimmunoassay (RIA), which utilized an antiserum generated against the beta-subunit ofhCG. Currently, serum hCG concentrations are widely used to diagnose and to evaluate normal and abnormal pregnancies (7-9). There are also reports in which the choice of treatment modality is based on the initial serum hCG concentration (9-12). Some authors use a urine hCG quantification method (13, 14). The metabolism of hCG and its subunits is partly renal and partly metabolic (15-17). The renal metabolism rates are different for the intact hCG dimer and its two subunits (15, 17). The correlation between the urine and serum levels for the intact hCG dimer is only weak (18). This weak correlation does not improve when related to creatinine excretions (18). Therefore, a qualitative hCG test in serum

Semiquantitative hCG with qualitative hCG tests

Fertility and Sterility

is more reliable than in urine (18, 19). In the past, serial dilutions to quantify hCG concentrations in urine have been used successfully. This method has not been described in serum samples. To employ the dilutional hCG range in serum instead of urine, the advantages of a quick qualitative hCG test might be combined with the accuracy of the standard serum quantitative hCG radioimmunoassay. MATERIALS AND METHODS

Two blood samples were collected from women supposed to be pregnant. One blood sample was tested by the routine quantitative hCG immunoassay (Delfia, hCG, time-resolved fluorescent immunoassay [FIA]; Wallac, Oy, Turku, Finland). The other sample was submitted to the laboratory for hCG analysis by the Tandem ICON 11 hCG (serum) Immuno-Enzy-Metric Assay (Hybritech, Liege, Belgium). Results of both assays were expressed in terms of the First International Reference Preparation (IRP) ofhCG. The serum tests with the Tandem ICON assay were performed as described in the manufacturer's instruction manual. A blue spot after 3 minutes was assessed as positive. Time span to positivity was measured. Standard dilutions varying between 1:10 and 1:400 of the test sera were made with hCG-negative serum. The test sera were diluted until their test results were negative. All tests were made in duplicate. The test result is assessed by observation of the test zone 3 minutes after dispensing the substrate reagent. There are four possibilities: [1] negative: a specimen does not produce a circular blue spot in the test zone; [2] positive:

An office semiquantitative serum human chorionic gonadotropin determination.

To compare the human chorionic gonadotropin (hCG) concentration, established by a standard serum quantitative hCG fluorescent immunoassay and a semiqu...
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