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Hook effect in Abbott i-STAT β-human chorionic gonadotropin (β-hCG) point of care assay
Urs Wilgen1, Carel J Pretorius1, Rehna S Gous2
1Pathology 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.
Unlabelled:
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.
Objectives:
Evaluation of the newly released Abbott i-STAT β-hCG point-of-care assay with the Beckman Coulter β-hCG laboratory assay in use.
Design And 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.
