Examination of the pregnancy-associated plasma protein-A assay on the Beckman Coulter Access(®) platform: suitability for use in first trimester Down's syndrome screening.
OBJECTIVE
To explore the clinical validity of the new Access(®) pregnancy-associated plasma protein-A (PAPP-A) assay for Down's syndrome screening.


METHODS
Academic hospital.


METHODS
Residual serum samples (n = 416) received for routine first trimester Down's syndrome screening (10-13 weeks) were retrieved from freezer storage and tested using two PAPP-A immunoassay methods. The new Access(®) assay was specifically compared, on a subset of these samples (n = 194), with an assay proven to give acceptable Down's syndrome screening performance, the PerkinElmer (PE) AutoDELFIA method. Access(®) PAPP-A levels were examined in relation to gestational age and maternal weight, and were compared with the PE method by regression and Bland-Altman analyses.


RESULTS
Access(®) PAPP-A assay results were highly correlated with the PE AutoDELFIA method (r = 0.97). PAPP-A levels obtained using the Access(®) assay increased with advancing gestational age and were inversely related to maternal weight, as expected. The distribution of multiples of the median (MoM) values fit a log Gaussian distribution and the standard deviation of the log MoM (0.2331) matched published estimates. PAPP-A MoM levels in Down's syndrome pregnancies (n = 6, median 0.30) showed the expected reduction.


CONCLUSIONS
Using an appropriate gestational age-specific median equation, the Access(®) PAPP-A assay is expected to perform acceptably in first trimester Down's syndrome screening.
Lambert-Messerlian
Geralyn
G
Department of Pathology and Laboratory Medicine, Division of Medical Screening and Special Testing, Women and Infants Hospital, 70 Elm St, Suite 2, Providence, RI 02903, USA. Gmesserlian@wihri.org
Palomaki
Glenn E
GE
Canick
Jacob A
JA
D004314:Down Syndrome / Q000097:blood* / Q000175:diagnosis*; D005260:Female; D006801:Humans; D007118:Immunoassay; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011266:Pregnancy-Associated Plasma Protein-A / Q000378:metabolism*; D015203:Reproducibility of Results
D011266:Pregnancy-Associated Plasma Protein-A