title: Assessment of the Abbott IMx assay system for the measurement of human chorionic gonadotropin levels in the treatment of ectopic pregnancy.
abstract: The rapid, accurate determination of serum human chorionic gonadotropin (beta-hCG) levels in the 900- to 2000-IU/L range is a critical element in the treatment of patients with suspected ectopic pregnancy. Using the Abbott IMx system (Abbott Laboratories, North Chicago, Ill), beta-hCG levels can be determined on an undiluted sample up to 1000 IU/L. A sample with beta-hCG level greater than 1000 IU/L is automatically diluted and the diluted sample redetermined. Unfortunately, employing a 1:200 fixed dilution can produce a working sample that contains an beta-hCG concentration that does not fall on a linear portion of the standard curve (<7.5 IU/L). This results in a calculated beta-hCG concentration (200 x observed value) that has high error (coefficient of variation up to 21.8%). Additionally, interfering substances in the reagents, which vary in quantity from lot to lot of reagents, further confound accurate beta-hCG determination by the system. Consequently, the Abbott IMx assay system cannot be used as recommended by the manufacturer for routine measurement of serum beta-hCG in the 900- to 2000-IU range. An alternate protocol employing at 1:10 dilution would allow a more accurate beta-hCG determination.
authors.affiliation: Department of Pathology and Laboratory Medicine, University of Pennsylvania Medical School, Philadelphia 19104.
authors.forename: D B
authors.initials: DB
authors.lastname: Goodman
authors.forename: M
authors.initials: M
authors.lastname: Bulley
authors.forename: M
authors.initials: M
authors.lastname: Hendricks
authors.forename: M
authors.initials: M
authors.lastname: Senior
mesh_terms: D001322:Autoanalysis; D006063:Chorionic Gonadotropin / Q000097:blood*; D005260:Female; D006801:Humans; D007124:Immunoenzyme Techniques / Q000592:standards*; D011247:Pregnancy; D011271:Pregnancy, Ectopic / Q000097:blood*; D011933:Reagent Kits, Diagnostic / Q000592:standards*; D012044:Regression Analysis; D015203:Reproducibility of Results
chemical_list: D006063:Chorionic Gonadotropin; D011933:Reagent Kits, Diagnostic