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Comparison of 2 Human Chorionic Gonadotropin Immunoassays Commercially Available for Monitoring Patients With Gestational Trophoblastic Disease
  1. Rafael Sanches dos Santos,
  2. Juliana Maria Quinalha de Souza, BSc, Biomedical Science*,,
  3. Antonio Braga, MD,
  4. Marcos Montanha Ramos, BSc, Biological Science*,,
  5. Rafael Cortés-Charry, MD§ and
  6. Izildinha Maestá, MD*,
  1. * Postgraduate Program in Gynecology, Obstetrics and Mastology and
  2. Trophoblastic Diseases Center, Botucatu Medical School, UNESP–São Paulo State University, Botucatu, São Paulo; and
  3. Rio de Janeiro Trophoblastic Disease Center (Maternity School of Rio de Janeiro Federal University, Antonio Pedro University Hospital of Fluminense Federal University), Rio de Janeiro, Rio de Janeiro, Brazil;
  4. § Department of Obstetrics and Gynecology, GTD Unit, University Hospital of Caracas, Central University of Venezuela, Caracas, Venezuela; and
  5. Department of Gynecology and Obstetrics, Botucatu Medical School, UNESP–São Paulo State University, Botucatu, São Paulo, Brazil.
  1. Address correspondence and reprint requests to Izildinha Maestá, MD, Department of Gynecology and Obstetrics, Botucatu Medical School, UNESP–São Paulo State University, Av. Prof. Montenegro s/n, Botucatu, São Paulo 18.618-970, Brazil. E-mail: imaesta{at}fmb.unesp.br.

Abstract

Objective The aim of this study was to compare serum human chorionic gonadotropin (hCG) levels in patients with gestational trophoblastic disease (GTD) using 2 commercially available hCG immunoassays.

Methods Serum samples were obtained from patients with GTD attending the Botucatu Medical School Trophoblastic Diseases Center of São Paulo State University (UNESP), from November 2014 to October 2015. Serum hCG levels were measured with both Architect i2000SR and Immulite 2000 XPi chemiluminescence assays. Serum hCG levels were compared against the null hypothesis. Agreement in clinical management decisions based on the hCG results was determined by comparing baseline hCG measurements and the hCG curves obtained with both assays.

Results Seventy-three patients with GTD were included in the analysis. Of these, 45 had hydatidiform mole and spontaneous remission, whereas 28 had gestational trophoblastic neoplasia (GTN). There was a perfect (zero difference) agreement in mean hCG levels between Immulite 2000 XPi and Architect i2000 when hCG is less than 100 mIU/mL. For hCG values greater than 100 mIU/mL, there was a significant difference between assays (P < 0.05), with levels measured via Architect i2000SR being higher than those measured by Immulite 2000 XPi in patients with hydatidiform mole/spontaneous remission (R2 = 90%, P < 0.01) and GTN (R2 = 98%, P < 0.01). Baseline clinical management decisions showed agreement in 100% (73/37) of cases (κ = 1.0, P < 0.001), whereas decisions based on hCG curve agreed in 98% (71/72) of cases (κ = 0.93, P < 0.001).

Conclusions Immulite 2000 XPi is the most frequently recommended assay for diagnosing and monitoring patients with GTD. However, our results suggest that because Immulite 2000 XPi and Architect i2000 show very similar performance in measuring hCG levels and in determining clinical management, Architect may be used as an alternative.

  • Gestational trophoblastic disease
  • Immunoassays
  • Serum hCG

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Footnotes

  • The authors declare no conflicts of interest.

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