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

OBJECTIVE: 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.

STUDY DESIGN: 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.

RESULTS: 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.

CONCLUSION: 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.

IMPLICATIONS: 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.