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

PAPP-A as a screening tool for assessment of gestational age before medication abortion in an intended-use population

Introduction: Prior studies indicate that PAPP-A could serve as a marker of gestational age (GA) with the potential to determine eligibility for medication abortion. The authors validated the relationship between PAPP-A and GA in an actual-use population. Materials & methods: The authors collected blood samples, medical histories and ultrasound-determined GA from patients presenting for abortion services. They measured PAPP-A using two immunoassays and assessed diagnostic accuracy for predicting GA ≥71 days. Results: The Ansh Labs and R&D Systems immunoassays produced an area under the ROC curve of 0.982 (95% CI: 0.958-0.994) and 0.986 (95% CI: 0.963-0.996), respectively, for predicting GA ≥71 days. Conclusion: This validation study in an intended-use population confirmed that PAPP-A has a strong ability to distinguish pregnancies above and below 71 days' gestation. Clinical trial registration: NCT04232189 (ClinicalTrials.gov).

Analytical Comparison of Pregnancy-Associated Plasma Protein-A (PAPP-A) Immunoassays for Biochemical Determination of Gestational Age

BACKGROUND

Accurate pregnancy dating is critical for maternal and child health and for counseling on safe and effective abortion methods. While last menstrual period and first trimester ultrasound are often used together to determine gestational age (GA), they have limited accuracy and availability, respectively. Prior studies have shown that pregnancy-associated plasma protein-A (PAPP-A) increases exponentially during pregnancy and has the potential to serve as a biochemical marker of GA. We aimed to analyze the relationship between sonographically determined GA and serum PAPP-A concentration measured by different immunoassays and to derive cutoff levels informative for the 70 days GA commonly recommended limit for medical abortion in outpatient settings.

METHODS

We compared technical characteristics of 4 commercially available PAPP-A immunoassays and tested 120 maternal serum samples (GA range: 34-231 days) along with contrived pool samples and traceable quality controls. These characteristics included area under the receiver operator characteristic (AUROC) plot, sensitivity and specificity based on cutoffs defined by the Youden Index, and likelihood ratios.

RESULTS

All 4 immunoassays had sensitivities and specificities ≥80%, and AUROC values ranging from 0.948 to 0.968. Marked differences among absolute PAPP-A values were noted depending on immunoassay. PAPP-A cutoff values at 70 days GA for each individual immunoassay were established along with procedural recommendations that increase equivalence among immunoassays.

CONCLUSIONS

Maternal serum PAPP-A levels correlated strongly with GA despite differences in immunoassay formats and absolute data output. Serum PAPP-A has biomarker potential for future development of a point-of-care test aimed at increasing access to medical abortion.

Advances in abortion care technology and management

PURPOSE OF REVIEW

To review emerging evidence specific to abortion care, including diagnostic testing and pain management.

RECENT FINDINGS

Recent advances in abortion care include improvements in gestational age dating, Rh status testing, and pain management methods. When ultrasound technology is available, the use of crown-rump length (CRL)-based dating is more accurate up to 13 weeks and composite CRL and biometry between 13 and 14 weeks. Evidence supports using updated fetal foot length-to-gestational age reference ranges for postprocedure gestational age confirmation. Serum tests for two placental proteins, pregnancy-associated plasma protein A and a disintegrin and metalloproteinase 12, show potential for identifying pregnancies with gestational age more than 70 days. Early research using flow cytometry demonstrates that fetal RBC exposure after first-trimester uterine aspiration is insufficient to cause maternal Rh-sensitization, supporting elimination of Rh testing and anti-D-immunoglobulin provision prior to 8 weeks gestation. Recent studies exploring pain management strategies have not generated a standardized approach. Auricular acupuncture appears to be promising.

SUMMARY

Emerging data on improvements in gestational age dating and eliminating laboratory testing prior to early abortion procedures could have important implications for expanding access to early abortion care and telemedicine. Person-centered, novel pain management modalities, such as auricular acupuncture, help to improve client experience, by addressing both pain and anxiety.