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Multicenter Study
. 2025 Jul 1;45(4):410-419.
doi: 10.3343/alm.2024.0362. Epub 2025 Mar 21.

Analytical Interference of Exemestane With Androstenedione Immunoassays

Marina Giralt  1   2 , Roser Ferrer  1   2 , Noelia Díaz-Troyano  1   2 , Belén Vega  3 , Manuel Luque-Ramírez  3 , Sílvia Martínez  4 , Bárbara Fernández  5 , Irene Martínez  6 , Aleix Fabregat  6 , Eulalia Urgell  7 , Ignacio Cardona  8 , Gregori Casals  6 , Héctor F Escobar-Morreale  3
Affiliations
Multicenter Study

Analytical Interference of Exemestane With Androstenedione Immunoassays

Marina Giralt et al. Ann Lab Med. .

Abstract

Background: Exemestane, an aromatase inhibitor commonly used for breast cancer treatment, shares structural similarities with sex steroids analyzed in clinical laboratories. We aimed to investigate the influence of exemestane cross-reactivity in the measurement of sex steroids across various immunoassays.

Methods: We conducted a multicenter study involving measurements of androstenedione, testosterone, estradiol, progesterone, and 17-hydroxyprogesterone in serum samples from women undergoing exemestane therapy (N=15; 25 mg/day). Measurements were performed using liquid chromatography-mass spectrometry (LC-MS) and various commercially available chemiluminescence immunoassays, ELISA, and radioimmunoassay. In-vitro cross-reactivity was assessed by adding exemestane and 17-hydroexemestane to serum samples.

Results: Patients undergoing exemestane therapy had markedly falsely elevated androstenedione results in all immunoassays evaluated (N=4), which correlated with serum exemestane levels. In-vitro experiments confirmed this interference to be caused by cross-reactivity with exemestane. Additionally, one immunoassay yielded falsely elevated estradiol results in 20% of patients. However, in-vitro experiments did not confirm this to be caused by cross-reactivity with exemestane or 17-hydroexemestane.

Conclusions: Exemestane cross-reacts with androstenedione immunoassays, causing falsely elevated results in treated patients. This analytical interference may raise unnecessary concerns, leading to expensive diagnostic workups.

Keywords: Cross-reactivity; Exemestane; Hyperandrogenism; Immunoassay; Immunochemiluminescence; Liquid chromatography-mass spectrometry.

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Conflict of interest statement

CONFLICTS OF INTEREST

None declared.

Figures

Fig. 1
Fig. 1. Molecular structures of exemestane, androstenedione, progesterone, 17-hydroxyprogestrone, 17-hydroexemestane, testosterone, and estradiol.
Fig. 2
Fig. 2. Correlation (A) and Bland–Altman bias (B) plots of serum androstenedione concentrations measured using Liaison, Cobas, Maglumi, and DiaSource RIA versus LC-MS/MS. Because of the very large differences between the immunoassay and LC-MS/MS results, the ratio versus LC-MS/MS is plotted. (C) Correlation plots of serum exemestane concentrations in treated patients with the bias of androstenedione results for Liaison, Cobas, Maglumi, and DiaSource RIA.
Abbreviations: LC-MS/MS, liquid chromatography-tandem mass spectrometry; RIA, radioimmunoassay.
Fig. 3
Fig. 3. Correlation (A) and Bland–Altman bias (B) plots of serum 17-hydroxyprogesterone concentrations measured using Maglumi, DRG ELISA, IBL ELISA, and DiaSource RIA versus LC-MS/MS. Correlation (C) and Bland–Altman bias (D) plots of serum testosterone concentrations measured using Cobas, Architect, and Atellica versus LC-MS/MS. Serum concentrations of progesterone (E) and estradiol (F) obtained with different commercial immunoassays versus LC-MS/MS.
Abbreviations: LC-MS/MS, liquid chromatography-tandem mass spectrometry; RIA, radioimmunoassay.
Fig. 4
Fig. 4. Serum concentrations of androstenedione, estradiol, testosterone, 17-hydroxyprogesterone, and progesterone obtained with different commercial immunoassays versus LC-MS/MS for pooled sera spiked with exemestane (A) or 17-hydroexemestane (B) at 0, 0.4, 4, and 40 ng/mL.
See this image and copyright information in PMC

References

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