Evaluation of DNA extracted from blood filter spots and eluates processed for enzyme linked immunosorbent assay (ELISA)

Dried filter blood spots have become a significant blood collection method for screening individuals for clinical purposes. When used for ELISAs, they are normally discarded after the blood has been eluted. However, they may still be useful for extraction of DNA for molecular- based assays. The aim of this work was to determine the integrity of DNA extracted from filter paper spots from which blood has initially been eluted for ELISA with sample dilution buffer (SDB) and phosphate buffered saline (PBS). DNA was extracted from the eluted filter spots, the eluate, and dried blood filter spots (controls) using spin column extraction. The quality and quantity of the extracted DNA was assessed and used for PCR to further evaluate their usefulness in molecular assays. Concentration of DNA obtained was dependent on the buffer used for processing the filter blood blots. Accounting for the DNA concentration obtained from dried blood spots, which were used as controls, DNA extracted from the already eluted blood spots were 32 times higher in PBS than SDB processed filter paper. The ratio was even higher for the eluates, which were 57 times higher in PBS than SDS eluates. SDB eluates had significantly higher average DNA concentration than their eluted filter paper, but their purity ratios were similar. 85% PCR success rate was achieved with the DNA samples. Useful DNA can be extracted from blood spots after it has been eluted with SDB. Although the DNA concentration and purity may be low, the DNA could be useful for rather simple PCR assays.