Immunofluorometric point-of-care assays for the detection of acute coronary syndrome-related noncomplexed pregnancy-associated plasma protein A.
BACKGROUND
We recently reported that the pregnancy-associated plasma protein A (PAPP-A) form specifically related to acute coronary syndromes (ACS) is not complexed with the proform of eosinophil major basic protein (proMBP). The aim of this study was to develop rapid point-of-care immunoassays for the measurement of the noncomplexed PAPP-A.


METHODS
We developed immunofluorometric noncompetitive dry-reagent assays for total PAPP-A with 2 PAPP-A subunit-specific monoclonal antibodies and for PAPP-A/proMBP complex with 1 PAPP-A subunit-specific antibody and 1 proMBP subunit-specific antibody. The concentration of noncomplexed PAPP-A was determined as the difference of the results obtained with the 2 assays.


RESULTS
The assays were linear from 0.5 to 300 mIU/L. The analytical detection limit and functional detection limit (CV <20%) were 0.18 mIU/L and 0.27 mIU/L for total PAPP-A assay and 0.23 mIU/L and 0.70 mIU/L for PAPP-A/proMBP assay, respectively. The total assay imprecisions were <10%, and recoveries were 88%-107% for both assays. The mean difference (95% limits of agreement) between the new total PAPP-A assay and a previously reported total PAPP-A assay was -3.2% (-45.7% to 39.3%; n = 546; P = 0.0019). In serum samples from 159 non-ACS individuals, median concentrations (interquartile range) were 2.42 (1.14) mIU/L for total PAPP-A, 2.20 (1.18) mIU/L for PAPP-A/proMBP, and 0.18 (0.63) mIU/L for noncomplexed PAPP-A. Total PAPP-A and PAPP-A/proMBP, but not noncomplexed PAPP-A, correlated with age (r = 0.290, P = 0.0002; r = 0.230, P = 0.0035; r = 0.075, P = 0.3483, respectively).


CONCLUSIONS
The new assays described revealed that noncomplexed PAPP-A is found only in negligible amounts in non-ACS samples.
Wittfooth
Saara
S
Department of Biotechnology,, University of Turku, Turku, Finland. sara.wittfooth@utu.fi
Qin
Qiu-Ping
QP
Lund
Juha
J
Tierala
Ilkka
I
Pulkki
Kari
K
Takalo
Harri
H
Pettersson
Kim
K
D000208:Acute Disease; D000328:Adult; D000368:Aged; D003327:Coronary Disease / Q000097:blood / Q000175:diagnosis*; D047093:Eosinophil Major Basic Protein / Q000097:blood; D005260:Female; D005455:Fluorescent Antibody Technique; D006801:Humans; D008297:Male; D008875:Middle Aged; D019095:Point-of-Care Systems; D011247:Pregnancy; D011266:Pregnancy-Associated Plasma Protein-A / Q000032:analysis* / Q000378:metabolism; D011485:Protein Binding; D011498:Protein Precursors / Q000097:blood; D013577:Syndrome
D011498:Protein Precursors; D047093:Eosinophil Major Basic Protein; D011266:Pregnancy-Associated Plasma Protein-A