Human chorionic gonadotropin discriminatory zone in ectopic pregnancy Does assay harmonization matter

Despite significant differences in human chorionic gonadotropin (hCG) concentrations across hCG immunoassays, an hCG discriminatory zone of 1,500–3,500 IU/L can be used for all but one commonly used hCG reagent platform.

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Diana Desai, M.D., Jun Lu, M.S., Sara P Wyness, B.S., Dina N Greene, Ph.D., Kalen N Olson, Ph.D., Carmen L Wiley, Ph.D., David G Grenache, Ph.D.

Volume 101, Issue 6, Pages 1671–1674



To determine the effect that lack of hCG assay harmonization has on the interpretation of a serum hCG concentration with regards to the hCG discriminatory zone.


A multisite method comparison study.


Clinical laboratories.


Eighty serum samples containing various concentrations of hCG.



Main Outcome Measure(s):

Concentrations of hCG obtained from seven hCG reagent platforms.


The hCG concentrations were significantly different across hCG reagent platforms. Seventy-one percent of assay pairs showed significant differences with samples selected based on hCG concentrations between 1,500 and 3,500 IU/L as determined by a comparative method. Relative to the comparative method, the calculated hCG discriminatory zones for five assays were within 9%, and one assay was within 40% of the target concentrations of 1,500 and 3,500 IU/L.


Despite significant differences in hCG concentrations across hCG immunoassays, an hCG concentration within a discriminatory zone of 1,500–3,500 IU/L can be used for all but one commonly used hCG reagent platform.

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Fertility and Sterility

Editorial Office, American Society for Reproductive Medicine

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