Hook effect in Abbott i-STAT β-human chorionic gonadotropin (β-hCG) point of care assay.
Point-of-care testing for β-hCG has been widely advocated to allow rapid diagnosis/exclusion of pregnancy in the emergency department. A quantitative blood β-hCG assay has the additional benefit of being able to monitor the viability of pregnancy, using serial measurements, to determine the appropriate expected increase in β-hCG levels over time (e.g. ectopic pregnancy), and aiding in determining if an intrauterine gestational sac should be visible on sonographic imaging.


OBJECTIVE
Evaluation of the newly released Abbott i-STAT β-hCG point-of-care assay with the Beckman Coulter β-hCG laboratory assay in use.


METHODS
Whole blood, plasma and serum samples with a wide range of β-hCG concentrations were analysed by both methods.


RESULTS
The Abbott I-STAT β-hCG compares favourably, can be performed on heparinised whole blood, plasma and serum, and shows acceptable accuracy and precision. However a hook effect at elevated β-hCG was shown in gestational trophoblastic disease as well as normal pregnancies.


CONCLUSIONS
The i-STAT β-hCG performs acceptably in its intended use in the early detection of pregnancy, but results should always be interpreted within the clinical context, as a hook effect may occur.
Pathology Queensland, Department of Chemical Pathology, Royal Brisbane and Women's Hospital, Herston Road, Herston 4029, Queensland, Australia; University of Queensland, School of Medicine, Brisbane, St. Lucia, 4072 Queensland, Australia. Electronic address: Urs.Wilgen@health.qld.gov.au.
Urs
U
Wilgen
Pathology Queensland, Department of Chemical Pathology, Royal Brisbane and Women's Hospital, Herston Road, Herston 4029, Queensland, Australia; University of Queensland, School of Medicine, Brisbane, St. Lucia, 4072 Queensland, Australia.
Carel J
CJ
Pretorius
Pathology Queensland, Department of Chemical Pathology, Royal Brisbane and Women's Hospital, Herston Road, Herston 4029, Queensland, Australia.
Rehna S
RS
Gous
Pathology Queensland, Department of Chemical Pathology, Royal Brisbane and Women's Hospital, Herston Road, Herston 4029, Queensland, Australia.
Cameron
C
Martin
Pathology Queensland, Department of Chemical Pathology, Royal Brisbane and Women's Hospital, Herston Road, Herston 4029, Queensland, Australia.
Vincent J
VJ
Hale
Pathology Queensland, Department of Chemical Pathology, Royal Brisbane and Women's Hospital, Herston Road, Herston 4029, Queensland, Australia.
Jacobus P J
JP
Ungerer
D001681:Biological Assay / Q000379:methods*; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000097:blood*; D005260:Female; D031901:Gestational Trophoblastic Disease / Q000097:blood; D006801:Humans; D011247:Pregnancy
D018997:Chorionic Gonadotropin, beta Subunit, Human
Gestational trophoblastic disease; Hook effect; Human chorionic gonadotropin (β-hCG); Point-of-care testing