of' 1Clinical. Pathology and 2Medicine, Cedars-. Sinai Medical Center, UCLA School of Medicine, 8700 Beverly. Blvd., Room B118, Los Angeles, CA 90048.
CLIN. CHEM. 40/10, 1944-1949
Four Rapid Serum-Urine Combination Assays of Choriogonadotropin (hCG) Compared and Assessed for Their Utility in Quantitative Determinations of hCG Suha H. Mishalani,1
and Glenn D. Braunstein2’3
We evaluated the performance of four visually read pregnancy tests (TestPack Plus hCG Combo, ICON II hCG, SureCell hCG-Serum/Urine and PregnaGen 1-Step) designed to detect increased concentrations of choriogonadotropin (hCG) in either serum or urine samples. The biochemical sensitivities and specificity in both serum and urine samples were similar for each kit. All kits correctly identified pregnancy serum samples: The TestPack Plus hCG Combo and SureCell hCG-Serum/Urine were 100% specific; the other two kits exhibited a few false-positive results. For urine samples the ICON II hCG test was 100% sensitive, and the other three were 99.5% sensitive, with false-positive urine results occasionally reported by the PregnaGen 1-Step and ICON II hCG tests. Quantitative hCG concentrations could be estimated in pregnancy serum samples, but not urine samples, through determination of the time elapsed from the sample application or addition of the final reagent to the first appearance of a positive result. Indexing Terms: pregnancy testing/intermethod ation, source of
Despite the number of commercially available tests for the qualitative measurement of choriogonadotropin (hCG) in serum or urine, relatively few are approved for hCG determination in serum and urine.4 Because no extensive comparative evaluation among these kits has been reported, we compared the performance of four commercial products with regard to each assay’s biochemical and clinical sensitivity and specificity. We also evaluated whether these assays could be used for quantitative measurements of serum and urine concentrations of hCG by measuring the time from the end of reagent addition to the appearance of a positive result.
Materials and Methods Samples. Serum samples were collected from 201 pregnant women, 100 postmenopausal women, 100 nonpregnant premenopausal women, and 100 men. Urine samples were collected from 200 pregnant women, 100 poatmenopausal women, 100 nonpregnant premenoDepartments of’ 1Clinical Pathology and 2Medicine, CedarsSinai Medical Center, UCLA School of Medicine, 8700 Beverly Blvd., Room B118, Los Angeles, CA 90048. 3Author for correspondence. Fax 310-289-5207. 4Nonstandard abbreviations: hCG, human choriogonadotropun (chorionic gonadotropin); WHO, World Health Organization; IS, International Standard; IRP, International Reference Preparation; FSH, follitropin (follicle-stimulating hormone); LH, lutropin (luteinizing hormone); and TSH, thyrotropin (thyroid-stimulating
hormone). Received May 12, 1994; accepted July 8, 1994. 1944
Vol. 40, No. 10, 1994
pausal women, and 100 men. The serum and urine samples were from different patients. Kits. The TestPack Plus hCG Combo kits (Abbott Labs., Abbott Park, IL) and the PregnaGen 1-Step kits (BioGenex, San Rarnon, CA) were provided by their manufacturers. The ICON II hCG kits (Hybritech, San Diego, CA), and SureCell hCG-SerumftJrine test kits (Eastman Kodak, Rochester, NY), were purchased. All kits were obtained from the same lot. Te8tPack Plus hCG Combo utilizes a goat polyclonal antibody to hCG-p subunit to capture the hCG and a mouse monoclonal anti-hCG-a subunit selenium-colloid complex to detect the hormone. Both ICON II and PregnaGen 1-Step kits use mouse monoclonal antibody to hCG-a subunit as capture antibodies. For detection, ICON II uses an enzyme-linked anti-hCG-$ subunit antibody; PregnaGen 1-Step utilizes anti-13 subunit-colloidal gold complex. SureCell hCG-Seruxn/lJrine uses a goat polyclonal antibody to hCG-p subunit to capture the hCG and a monoclonal antibody targeted to the intact hCG molecule coupled to enzyme for the detection of the hormone. The methods presented in the instruction booklets were followed strictly. Comparison methods. Our previously described radioimmunoassays of hCG in serum and urine were used to quanti1r the hCG in all true- and false-positive and false-negative serum and urine samples (1, 2). Both assays measure intact hCG, free hCG-p subunit, the (3-core fragment of hCG, and “nicked” hCG. CR127 hCG was used as a standard and was iodinated with 1251 for use as the tracer; the antibody to hCG p subunit, SB6, was used as the primary antibody (both reagents were obtained as a gift of the National Hormone and Pituitary Program, National Institutes of Health, Rockville, MD). The sensitivity (detection limit) of the serum assay is 5 lU/L relative to the World Health Organization Second International Standard (WHO 2nd IS) or 7.5 lU/L relative to the WHO 3rd IS. The intra- and interassay CVs in serum are 6.6% and 8.2%, respectively, with values