Analytical performance evaluation of the i-STAT Total β-human chorionic gonadotropin immunoassay.
BACKGROUND
The ability to perform quantitative hCG testing in whole blood at the point-of-care is desirable. The purpose of this study was to perform an analytical validation of the Abbott i-STAT Total β-hCG test.


METHODS
Whole blood, plasma, and serum samples were prepared by the addition of hCG and were used to evaluate precision, linearity, analytical sensitivity, accuracy, the high-dose hook effect, and dilution recovery.


RESULTS
Imprecision was highest with whole blood (CV = 16.0% and 6.7% at 10 and 1184 IU/l, respectively) and lowest in serum (CV = 8.1% and 4.3% at 11 and 1305 IU/l, respectively). The limits-of-quantitation were 8 and <5 IU/l for whole blood and both plasma and serum, respectively. The assay was linear between 5 and 2000 IU/l in all sample types (R(2) ≥ 0.998). i-STAT results agreed most closely with the Architect Total β-hCG assay and with greater differences observed with Beckman DxI Total βhCG and Roche Cobas e601 hCG+β assays (mean differences across all sample types were 9.3% and 12.3%, respectively). A high-dose hook effect was observed at concentrations > 400,000 IU/l. Accuracy was achieved in samples diluted with serum but not saline.


CONCLUSIONS
The i-STAT Total β-hCG test demonstrates acceptable performance for quantifying hCG in whole blood, plasma and serum.
Department of Pathology, University of Utah School of Medicine, Salt Lake City, UT, USA.
Aleksandra M
AM
Sowder
Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO, USA.
Melanie L
ML
Yarbrough
Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO, USA.
Robert D
RD
Nerenz
Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO, USA.
John V
JV
Mitsios
ARUP Laboratories, Salt Lake City, UT, USA.
Rachel
R
Mortensen
Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO, USA; Department of Obstetrics and Gynecology, Washington University School of Medicine, St. Louis, MO, USA.
Ann M
AM
Gronowski
Department of Pathology, University of Utah School of Medicine, Salt Lake City, UT, USA; ARUP Institute for Clinical and Experimental Pathology, Salt Lake City, UT, USA. Electronic address: david.grenache@path.utah.edu.
David G
DG
Grenache
D000328:Adult; D002138:Calibration; D006063:Chorionic Gonadotropin / Q000097:blood*; D005260:Female; D006801:Humans; D007118:Immunoassay / Q000592:standards*; D057230:Limit of Detection; D019095:Point-of-Care Systems; D011258:Pregnancy Tests / Q000592:standards*; D012016:Reference Values; D015203:Reproducibility of Results
D006063:Chorionic Gonadotropin
Human chorionic gonadotropin; Point-of-care; Pregnancy test; Quantitative; Whole blood