In the news

This study aimed to determine whether it is feasible to perform useful global gene expression profiling on archived blood spot samples.

Blood spot samples between 6 months and 3 years old were collected from archives and tested, along with specimens from healthy controls on Guthrie cards (the term for blood samples, typically taken from newborns, spotted onto specially manufactured filter paper). RNA was extracted, purified and amplified, followed by microarray and gene expression analysis.

Around 9000 expressed genes per sample could be detected by the commercially available technique used in this study, compared with the 3500 genes the same team were able to identify using custom-made methods in their previous research. This study also confirmed that 3mm blood spot punches (the sample size taken from the card by the automated method used) are sufficient for generating gene expression profiles.

The researchers conclude that they have successfully established a new assay to obtain gene expression profiles from blood spot samples on Guthrie cards, and that this could open new opportunities to utilise archived specimens in large scale epidemiology studies.  They point out that in terms of efficiency and cost it makes sense to develop a means to use the pre-existing and comprehensive archive of newborn blood spots, rather than to devise methods that depend upon gathering new samples. The method used in this study was nearly 3 times as effective as the method used in their previous study, and is reproducible. They intend next to apply the technique to blood spot samples that have been stored for periods of up to 20 years.

This technique has potentially significant implications for the epidemiological study of disease, in that it allows the exploitation of a ready resource that doesn’t require the expense and difficulty of obtaining fresh samples. Because the method also uses existing and commercially available tools it could be easily be employed by others.

Guthrie cards have been used for 2-3 decades to collect blood for mandatory newborn screening programs in the US, Europe, South America, Australia and Japan amongst others. The successful use of the technique in this study thus means that a potentially vast archive could become available for population health research. However, archived cards are kept in a wide variety of storage conditions depending on region and country, which could conceivably mean that samples from some regions and archives may not be useable. The researchers’ forthcoming study of older archived blood spot samples may clarify the effect of such discrepancies in storage methods.