Methodological aspects of dried blood spot sampling for the determination of isoprostanoids and prostanoids

Dried Blood Spot (DBS) analysis is a well-established practice for monitoring newborns in neonatal units because of the non-invasive collection of a very limited blood volume. Unfortunately, the haematocrit level and the drop volume can adversely affect the quality of the analytical data. For this reason, we performed an in-depth comparison of non-volumetric and volumetric sampling (e.g. Minivette® POCT microcapillary, and the microfluidic-based systems HemaXisTM DB and Capitainer-B) for the DBS analysis of the isoprostanoids 8-iso prostaglandin F2α and 8-iso prostaglandin E2, and prostaglandin E2, which represent well recognized indexes of oxidative stress and inflammation. Results highlighted a significant impact of drop volume on the analytical performances for the non-volumetric approach due to the inhomogeneous distribution of the analytes across the DBS. The innovative addition of labelled internal standards (ISs) on the filter paper before sampling did not circumvent the problem, as ISs did not accurately mimic the spreading of analytes in the DBS. Differently from HemaXisTM DB and Capitainer-B, the Minivette® POCT device showed an almost quantitative recovery with an overall variability of about 15%, and resulted the best option for an easy and reliable DBS collection in the clinic. Our procedure was used for the determination of the three metabolites in preterm newborns suffering from Patent Ductus Arteriosus (PDA). During our longitudinal monitoring, most of the preterm newborns with PDA showed a marked decrease (40–60%) of target analytes upon ibuprofen therapy, suggesting the potential involvement of the isoprostanoids and prostanoids in promoting drug responsiveness and ductal closure.