105 - The Laboratory role in pregnancy diagnosis
Autor(s): A. Fortunato
Issue: RIMeL - IJLaM, Vol. 6, N. 2, 2010 (MAF Servizi srl ed.)
Page(s): 105-110
Background. At the beginning of eighties human chorionic gonadotropin (hCG) immunoassays availability significatively improved the laboratory role in pregnancy diagnosis. Increased methods sensitivity of blood tests and urine point of care or home pregnancy tests enables not only early pregnancy detection and demonstration of hCG secretion in other physiopathology conditions but also the oversensitiveness to interference mainly for urine samples. Methods. Analytical and interpretative aspects of hCG detection related to the molecular heterogeneity and the need of methods standardization are discussed. To evaluate the performances of six different commercial pregnancy tests we report results obtained in urine samples with hCG concentration between 0 and 2000 IU/L for a total of 500 assays. Results. hCG molecular heterogeneity is due both to structure variants and carbohydrate content, the consequence is the use of nonstandard nomenclature for hCG variants, absence of purified standards to achieve accurate calibration and discrepant characterizations of hCG variants that are recognized by different hCG immunoassays. Our data for the pregnancy test methods comparison demonstrate that all samples, with hCG concentration between 15 and 70 IU/L, showed at least one disagreeing clinical result. Conclusions. With different immunoassays giving different results for the same specimens, hCG measurement standardization is an important problem and recently it has been a topic of great discussion. Also results obtained with urine quick tests aren’t always easy to interpret, also if tests are performed by skilled technicians, and often manufacturer declared sensitivity is better than that demonstrated in our study.