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.
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
Geralyn
G
Lambert-Messerlian
Glenn E
GE
Palomaki
Jacob A
JA
Canick
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