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

Capsule:
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.

Authors:
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

Abstract:

Objective:
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.

Design:
A multisite method comparison study.

Setting:
Clinical laboratories.

Patient(s):
Eighty serum samples containing various concentrations of hCG.

Intervention(s):
None.

Main Outcome Measure(s):
Concentrations of hCG obtained from seven hCG reagent platforms.

Result(s):
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.

Conclusion(s):
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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