A sensitive enzyme immunoassay for pregnancy-associated plasma protein A (PAPP-A): a possible first trimester method of screening for Down syndrome and other trisomies

1995 ◽  
Vol 256 (4) ◽  
pp. 185-192 ◽  
Author(s):  
N. A. Bersinger ◽  
A. Zakher ◽  
U. Huber ◽  
G. Pescia ◽  
H. Schneider
Keyword(s):  
Down Syndrome ◽  
Enzyme Immunoassay ◽  
Plasma Protein ◽  
Protein A ◽  
First Trimester

Four Years' Experience With an Interlaboratory Comparison Program Involving First-Trimester Markers of Down Syndrome

2010 ◽  
Vol 134 (11) ◽  
pp. 1685-1691
Author(s):  
Glenn E. Palomaki ◽  
George J. Knight ◽  
Geralyn Lambert-Messerlian ◽  
Jacob A. Canick ◽  
James E. Haddow
Keyword(s):  
Down Syndrome ◽  
Chorionic Gonadotropin ◽  
Plasma Protein ◽  
Human Chorionic Gonadotropin ◽  
Interlaboratory Comparison ◽  
Protein A ◽  
First Trimester ◽  
Nuchal Translucency ◽  
Second Trimester ◽  
Coefficients Of Variation

Abstract Context.—We initiated a voluntary, self-funded interlaboratory comparison program in the fall of 2005 because no proficiency testing program was available to laboratories in North America offering first-trimester, combined serum and ultrasound, Down syndrome screening. Objectives.—To evaluate the first 4 years of the interlaboratory comparison program against stated goals, to identify areas of concern, and to create new initiatives as indicated. Design.—Five serum samples are distributed 3 times a year to be tested for pregnancy-associated plasma protein A, human chorionic gonadotropin or its β subunit, and dimeric inhibin-A; participants convert these results into multiples of the median. Patient histories include nuchal translucency information that enables the calculation of the risk of Down syndrome. Also included are educational components linked to interlaboratory comparison program results. Assessment of integrated (first- and second-trimester markers) risks is accomplished by having participants combine interlaboratory comparison program results with their results from a second-trimester proficiency testing program administered by the College of American Pathologists. Results.—The precision profile for pregnancy-associated plasma protein A shows decreasing coefficients of variation with increasing pregnancy-associated plasma protein A concentrations and multiples of the median (25% to 11% and 30% to 15%, respectively). In contrast, coefficients of variation are a relatively constant 12% throughout the entire range of human chorionic gonadotropin results. On a logarithmic scale, the median coefficient of variation of the risk of Down syndrome is 9%. Conclusions.—Participants in the interlaboratory comparison program reliably measure analytes, compute multiples of the median, and calculate consistent Down syndrome risks. Assays for the measurement of pregnancy-associated plasma protein A are not standardized and are less precise than those for human chorionic gonadotropin. Participants calculate reliable median equations given sonographer-specific sets of paired crown-rump length and nuchal translucency measurements.

scholarly journals Point-of-Care Time-resolved Immunofluorometric Assay for Human Pregnancy-associated Plasma Protein A: Use in First-Trimester Screening for Down Syndrome

2002 ◽  
Vol 48 (3) ◽  
pp. 473-483 ◽  
Author(s):  
Qiu-Ping Qin ◽  
Michael Christiansen ◽  
Kim Pettersson
Keyword(s):  
Down Syndrome ◽  
Confidence Interval ◽  
Plasma Protein ◽  
Whole Blood ◽  
Point Of Care ◽  
Protein A ◽  
First Trimester ◽  
Time Resolved ◽  
Lanthanide Chelate ◽  
One Stop

Abstract Background: Screening for Down syndrome in the first trimester by a combination of fetal nuchal translucency thickness and maternal serum pregnancy-associated plasma protein A (PAPP-A) and free β-human chorionic gonadotropin has been shown to be effective and efficient. We aimed to develop a fast point-of-care assay that could be placed in one-stop clinics for the measurement of PAPP-A. Methods: We developed a two-site, one-step assay that uses two monoclonal antibodies (mAbs) to PAPP-A, based on a dry-reagent, all-in-one immunoassay concept with a stable fluorescent lanthanide chelate and time-resolved fluorometry. One antibody (mAb 10E1) was biotinylated, and the other (mAb 234-5) was europium-labeled, both via the ε-amino groups of surface lysine residues. The assay was performed on an AIO immunoanalyzer at 36 °C in single, streptavidin-coated microtitration wells that contained the dry reagents. PAPP-A, either in free or complexed form, was detected by the antibodies used. Results: The assay procedure required 20 min and used 10 μL of sample. The calibration curve was linear from 5 to 10 000 mIU/L. The detection limit was 0.5 mIU/L. Intra- and interassay imprecision (CV) was ≤4.3% and 8.3%, respectively, for whole blood, plasma, or serum samples. Recovery was 93–96% for serum, 95–108% for heparin-derived whole blood, and 98–103% for heparin-derived plasma. Parallelism was observed in all three matrices. Results correlated [slope = 0.85 (confidence interval, 0.82–0.87); intercept = −33 (confidence interval, −58 to −9); Sy|x = 85 mIU/L; r = 0.991; n = 100] with those obtained by a Delfia assay. Heparin did not affect the assay, but EDTA markedly reduced PAPP-A values. PAPP-A was stable at 4 °C for at least 18 days in serum and for 8 days in heparin-derived whole blood or plasma. Conclusions: The present assay appears suited for use in one-stop clinics for screening for Down syndrome in the first trimester, with results available within 1 h.

scholarly journals Double-monoclonal immunofluorometric assays for pregnancy-associated plasma protein A/proeosinophil major basic protein (PAPP-A/proMBP) complex in first-trimester maternal serum screening for Down syndrome

1997 ◽  
Vol 43 (12) ◽  
pp. 2323-2332 ◽  
Author(s):  
Qiu-Ping Qin ◽  
Michael Christiansen ◽  
Claus Oxvig ◽  
Kim Pettersson ◽  
Lars Sottrup-Jensen ◽  
...  
Keyword(s):  
Down Syndrome ◽  
Plasma Protein ◽  
Basic Protein ◽  
Protein A ◽  
First Trimester ◽  
Maternal Serum ◽  
Major Basic Protein ◽  
Maternal Serum Screening ◽  
Detection Rates ◽  
Serum Screening

Abstract Four double-monoclonal time-resolved immunofluorometric assays (TrIFMAs) have been developed for the specific determination of pregnancy-associated plasma protein A/proeosinophil major basic protein (PAPP-A/proMBP) complex in first-trimester maternal serum samples. The assays have a functional sensitivity of <4 mIU/L and a working range from 4 to 1000 mIU/L. These 4 assays, together with a polyclonal sandwich TrIFMA, were compared for their ability to discriminate between normal pregnancies (n = 149) and pregnancies carrying a Down syndrome fetus (n = 36) in maternal serum screening samples from gestational weeks 4–13. In 26 Down syndrome pregnancies from gestational weeks 7–12, the median PAPP-A multiples of the median concentration in controls (MoMs) determined by monoclonal antibody combinations 234–3/234–2*, 234–4/234–2*, 234–4/234–5*, and 234–5/234–6* were 0.35, 0.37, 0.42, and 0.44, respectively, whereas the median MoM determined by the polyclonal assay was 0.56. ROC curve analysis also showed that better overall diagnostic accuracy and detection rates were achieved by the monoclonal TrIFMAs than by the polyclonal TrIFMA. This report is the first to describe assays that specifically measure PAPP-A/proMBP complex without possible interference from other proMBP-containing complexes.

Pregnancy-associated plasma protein A (PAPP-A): measurement by highly sensitive and specific enzyme immunoassay, importance of first-trimester serum determinations, and stability studies

1995 ◽  
Vol 7 (6) ◽  
pp. 1419 ◽  
Author(s):  
NA Bersinger ◽  
P Marguerat ◽  
G Pescia ◽  
H Schneider
Keyword(s):  
Enzyme Immunoassay ◽  
Plasma Protein ◽  
Protein A ◽  
First Trimester ◽  
Maternal Serum ◽  
Potential Candidate ◽  
Second Trimester ◽  
Freezing And Thawing ◽  
Control Serum ◽  
Repeated Freezing

It has recently been established that maternal serum pregnancy-associated plasma protein A (PAPP-A) was reduced in pregnancies with fetal Down syndrome in the first but not in the second trimester of gestation. In comparison with two other placental proteins, human chorionic gonadotrophin and pregnancy-specific beta 1-glycoprotein, an explanation for this can be formulated based on the large molecular weight of PAPP-A. With the increasing clinical demand for fetal abnormalities to be diagnosed in the first rather than in the second trimester of pregnancy, maternal serum PAPP-A is a strong potential candidate for being used in routine trisomy screening. We have developed a sensitive enzyme immunoassay (ELISA) intended at smaller laboratories due to its long shelf life. Here we show that repeated freezing and thawing, or the addition of iodoacetate (5 mM) did not affect the results, at both high or low concentration of PAPP-A. It is also possible to introduce the serum into the test as a dry sample on blotting paper, easily posted in an envelope. A decrease of 21% was observed after such dry storage for three weeks at room temperature, which can be compensated for by the inclusion of a dried control serum, mailed with the sample(s).

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