High-dose hook effect in six automated human chorionic gonadotrophin assays.
BACKGROUND
The high-dose hook effect is a well-known phenomenon of two-site immunoassays including those for human chorionic gonadotrophin (hCG). We investigated the occurrence of a high-dose hook effect in six routinely available hCG assays using a sample with a total hCG concentration of approximately 3,600,000 IU/L.


METHODS
Dilutions of a sample with high hCG concentration were analysed using six common methods: Advia Centaur, Immulite 2000, Dimension RxL, Unicel DxI 800, Roche E170 and Abbott Architect. The measured concentrations and corresponding assay signals were obtained for each method. Performance was compared with manufacturer claims.


RESULTS
Four of the tested platforms demonstrated a clear high-dose hook effect, while the other methods showed no hook effect at the highest level tested.


CONCLUSIONS
Our results indicate that the hook effect may occur in some hCG assays, although the risk of reporting falsely low results was in most cases at higher concentrations than those indicated in manufacturers' product information. Assay design plays a major role in its occurrence. Laboratories should be aware of the assay limitations in this regard.
Al-Mahdili
Huda A
HA
Department of Chemical Pathology, SydPath, St Vincent's Hospital, Victoria St., Darlinghurst, Australia.
Jones
Graham R D
GR
D016477:Artifacts; D001331:Automation; D006063:Chorionic Gonadotropin / Q000032:analysis* / Q000276:immunology; D005188:False Negative Reactions; D006801:Humans; D007118:Immunoassay / Q000295:instrumentation / Q000379:methods*; D008297:Male
D006063:Chorionic Gonadotropin