Cross-Analysis of the Quantitative Determination of Uirinary Human Chorionic Gonadotropin (GCG) by Means of Automated Immunoassay and Radioimmunossay Techniques
Chicco, Giacomo Franco
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A substance commonly associated with pregnancy-testing is the hormone Human Chorionic Gonadotropin, a glycoprotein produced by the trophoblast, easily detectable in the maternal urine five weeks after the last menstrual period through common immunological techniques. Because of its early appearance, this hormone has become the classical substance tested for when a proof of pregnancy is required. Moreover, it has also been used for the monitoring of the risk of spontaneous abortion and for the diagnosis and prognosis of most trophoblastic diseases. In the past, the classical method for the detection of HCG had been a adioimmunological technique developed by Wide in 1962. This method, based on the detection of the beta subunit of the hormone, was found, in the years, to be very lengthy and complicated. Today, routine pregnancy testing is carried out by rapid immunological test-tube assays based on the agglutination-inhibition reaction. This method, though, presents itself as very inaccurate and unreliable for the quantitative measurement of HCG in urine. It was only in 1979 that Martorana and Castelli introduced a new method for pregnancy testing which combined the simple immunological test-tube assay to a rotative analyzer. The speed with which assays can be done and, above all, an increase in reliability of the quantitative measurement of HCG by immunological methods. The purpose of this research was to test the accuracy and reliability of this new method by cross-analyzing the clinical results obtained in parallel with the radioimmunoassay technique; further, the extent to which this type of assay can be adapted to the routine work of a laboratory of analysis of a city hospital was also questioned. At the end of the experiment, it was discovered that there was not a good correspondence between the results of the two methods. Consequently, a series of determinations using the semi-quantitative test-tube assay were performed in order to establish the validity of the automated immunoassay. In conclusion, the apparent non-specificity of the automated immunoassay results and its possible causes were briefly analyzed.