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Abstract: SA-PO1099

Human Chorionic Gonadotropin (hCG) in Dialysis Patients

Session Information

Category: Pathology and Lab Medicine

  • 1502 Pathology and Lab Medicine: Clinical

Authors

  • Haninger-Vacariu, Natalja, Medical University of Vienna, Vienna, Austria
  • Herkner, Harald, Medical University Vienna, Vienna, Austria
  • Lorenz, Matthias, Dialysis Centre Vienna, Vienna, Austria
  • Saemann, Marcus D., Wilhelminen Hospital, Vienna, Austria
  • Vychytil, Andreas, Medical University of Vienna, Vienna, Austria
  • Jansen, Martin, Hospital St. John of God, Vienna, Austria
  • Marculescu, Rodrig, Medical University of Vienna, Vienna, Austria
  • Kramar, Reinhard, Austrian Dialysis and Transplant Registry, Kematen, Austria
  • Sunder-Plassmann, Gere, Medical University Vienna, Vienna, Austria
  • Schmidt, Alice, Medical University of Vienna, Vienna, Austria
Background

The FDA mandates pregnancy testing before and 8 days after initiation of therapy with MMF/MPA because its use in pregnancy is associated with an increased risk of miscarriage and congenital defects. However, a few case reports showed hCG to be elevated in transplant candidates resulting in refusal of transplantation.

Methods

We examined hCG serum concentrations in female dialysis patients, 18-50 years of age, and defined fertility status according to STRAW criteria. We classified hCG positive above a cut-off at 5 mIU/l. For an enhanced index test we classified hCG positive above a cut-off at 5 mIU/l for fertile patients and 14 mIU/l for non-fertile patients to calculate diagnostic test accuracy. We estimated the ideal cut-off for hCG using Liu's method with bootstrapped 95% CIs. We report estimates for hCG as a diagnostic test and predictors for elevated hCG using multivariable linear regression.

Results

Among 71 women two (2.8 %) were pregnant presenting with elevated hCG serum concentrations. We observed hCG concentrations greater than 5 mIU/ml, potentially indicating pregnancy, in 10 further patients. A hCG serum concentration > 5 mIU/ml had a sensitivity of 100% (95% CI: 100 to 100), a specificity of 86% (95% CI: 77 to 94), a positive predictive value (PPV) of 17% (95% CI: 8 to 25) and a negative predictive value (NPV) of 100% (95% CI: 100 to 100) for the diagnosis of pregnancy. Using a hCG cut-off of > 14 mIU/ml for non-fertile patients sensitivity and NPV did not change, the specificity increased to 93% (95% CI: 87 to 99) and the PPV was 29% (95% CI: 18 to 39). Excluding 23 non-fertile patients resulted in a specificity of 98% (95% CI: 94 to 100) and a PPV of 67% (95% CI: 53 to 80) whereas sensitivity and NPV did not change. The ideal hCG cut-off was 25.0 mIU/ml (95% CI: 17 to 33). Pregnancy (coefficient: 8.7; 95% CI: 6.6 to 10.7; p<0.001) and fertility (coefficient: -2.7; 95% CI: -3.5 to -1.8; p<0.001), but not age (coefficient -0.03; 95% CI: -0.08 to 0.01; p=0.13) were independent predictors of log transformed hCG.

Conclusion

hCG is elevated > 5 mIU/ml in 14,5% of non-pregnant dialysis patients of child-bearing age. In fertile women this cut-off can be used to exclude pregnancy. For our population the ideal hCG cut-off was 25 mIU/ml.