Comparison of different blood collection, sample matrix, and immunoassay methods in a prenatal screening setting

Improved prediction of gestational hypertension by inclusion of placental growth factor and pregnancy associated plasma protein-a in a sample of Ghanaian women

BACKGROUND

We assessed whether adding the biomarkers Pregnancy Associated Plasma Protein-A (PAPP-A) and Placental Growth Factor (PlGF) to maternal clinical characteristics improved the prediction of a previously developed model for gestational hypertension in a cohort of Ghanaian pregnant women.

METHODS

This study was nested in a prospective cohort of 1010 pregnant women attending antenatal clinics in two public hospitals in Accra, Ghana. Pregnant women who were normotensive, at a gestational age at recruitment of between 8 and 13 weeks and provided a blood sample for biomarker analysis were eligible for inclusion. From serum, biomarkers PAPP-A and PlGF concentrations were measured by the AutoDELFIA immunoassay method and multiple of the median (MoM) values corrected for gestational age (PAPP-A and PlGF) and maternal weight (PAPP-A) were calculated. To obtain prediction models, these biomarkers were included with clinical predictors maternal weight, height, diastolic blood pressure, a previous history of gestational hypertension, history of hypertension in parents and parity in a logistic regression to obtain prediction models. The Area Under the Receiver Operating Characteristic Curve (AUC) was used to assess the predictive ability of the models.

RESULTS

Three hundred and seventy three women participated in this study. The area under the curve (AUC) of the model with only maternal clinical characteristics was 0.75 (0.64-0.86) and 0.89(0.73-1.00) for multiparous and primigravid women respectively. The AUCs after inclusion of both PAPP-A and PlGF were 0.82 (0.74-0.89) and 0.95 (0.87-1.00) for multiparous and primigravid women respectively.

CONCLUSION

Adding the biomarkers PAPP-A and PlGF to maternal characteristics to a prediction model for gestational hypertension in a cohort of Ghanaian pregnant women improved predictive ability. Further research using larger sample sizes in similar settings to validate these findings is recommended.

Dried blood spot measurement of pregnancy-associated plasma protein A (PAPP-A) and free β-subunit of human chorionic gonadotropin (β-hCG) from a low-resource setting

OBJECTIVES

The objectives of the article is to compare pregnancy-associated plasma protein A (PAPP-A) and free β-subunit of human chorionic gonadotropin (β-hCG) concentrations in dried blood spots (DBSs) with serum of samples obtained from a public hospital in a low-resource setting and to evaluate their stability.

METHODS

Serum and DBS samples were obtained by venipuncture and finger prick from 50 pregnant participants in a cohort study in a public hospital in Accra, Ghana. PAPP-A and β-hCG concentrations from serum and DBS were measured with an AutoDELFIA® (PerkinElmer, PerkinElmer, Turku, Finland) automatic immunoassay. Correlation and Passing-Bablok regression analyses were performed to compare marker levels.

RESULTS

High correlation (>0.9) was observed for PAPP-A and β-hCG levels between various sampling techniques. The β-hCG concentration was stable between DBS and serum, PAPP-A concentration consistently lower in DBS.

CONCLUSION

Our findings suggest that β-hCG can be reliably collected from DBS in low-resource tropical settings. The exact conditions of the clinical workflow necessary for reliable PAPP-A measurement in these settings need to be further developed in the future. These findings could have implications for prenatal screening programs feasibility in low-income and middle-income countries, as DBS provides an alternative minimally invasive sampling method, with advantages in sampling technique, stability, logistics, and potential application in low-resource settings.