Sensitivity and specificity of placental proteins for gestational age screening: An exploratory study

To examine the possibility that serum or urine concentrations of pregnancy-associated plasma protein A (PAPP-A), a disintegrin and metalloproteinase 12 (ADAM-12), placental growth factor (PlGF), human placental lactogen (HPL), glypican-3, pregnancy specific beta-1-glycoprotein 1 (PSG-1) or prolactin could predict gestational age (GA) >70 days, the currently recommended limit for medical abortion in the United States.

In this exploratory observational study, we collected serum and urine specimens from 245 healthy individuals with singleton intrauterine pregnancies at GA <40 weeks by ultrasound. We assayed the serum specimens for all seven proteins and the urine specimens for PAPP-A and ADAM-12. We used scatterplots and receiver operating characteristic curves to identify a concentration for each protein that would differentiate GAs above and below 70 days.

All seven proteins showed significant ability to distinguish GAs >70 days from earlier gestations. A PAPP-A concentration ≥5.591 ng/ml provided 100% sensitivity and 90% specificity for identifying GAs >70 days. An ADAM-12 concentration of ≥3.11 ng/ml provided 98.5% sensitivity and 77% specificity for identifying GAs >70 days. Serum concentrations of the other compounds showed less diagnostic discrimination. PAPP-A was not detected in urine, and urinary ADAM-12 concentrations were not useful in identifying GAs above 70 days.

PAPP-A and ADAM-12 showed considerable promise as bases for a sensitive and specific serum test for identifying pregnancies with GA >70 days. If these results are confirmed by future research, such a test could obviate the need for routine ultrasound before medical abortion.

Two placental proteins, PAPP-A and ADAM-12, showed considerable promise as bases for a serum test for identifying pregnancies with gestational age >70 days. Such a test could be highly useful in screening patients for eligibility for medical abortion.