Archived Unfrozen Neonatal Blood Spots Are Amenable to Quantitative Gene Expression Analysis

BACKGROUND: State laws in the USA mandate that blood be drawn from all newborn infants to screen for health-threatening conditions. These screening assays consume only a small portion of the blood samples, which are collected on filter paper ('Guthrie') cards. Many states archive unused blood spots, often in unrefrigerated storage. OBJECTIVES: While individual RNA transcripts have been identified from archived neonatal blood spots, no study to date has performed quantitative analysis of archived blood spot RNA. METHODS: We demonstrate that RNA can be isolated and amplified from newborn blood spots stored unfrozen for as long as 9 years, and can be analyzed by microarray and qPCR. RESULTS: Microarray assays of archived neonatal blood spots consistently detected 3,000-4,000 expressed genes with correlations of 0.90 between replicates. Blood spot mRNA is amenable to qPCR and we detected biologically relevant expression levels of housekeeping and immune-mediating genes. CONCLUSIONS: These experiments demonstrate the feasibility of using blood spots as a source of RNA which can be analyzed using quantitative microarray and qPCR assays. The application of these methods to the analysis of widely collected biological specimens may be a valuable resource for the study of perinatal determinants of disease development.