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Stability of genomic DNA in dried blood spots stored on filter paper.

The stability of DNA in dried blood samples obtained from the neonatal screening program in Thailand was retrospectively studied in order to determine the conditions necessary for the long term storage of samples for DNA banking. Specimens from 1991 to 2001, which had been kept in the ambient conditions at the Department of Medical Science, Ministry of Public Health, Thailand, were randomly sampled and used for the study. Genomic DNA was extracted from the samples and DNA fragments of the PAX8 and beta-globin genes were amplified by PCR to determine DNA stability. The study showed that 255-bp and 674-bp fragments of the PAX8 gene could be amplified from all the samples. The DNA fragment of 1,039 bp of the beta-globin gene could be detected in all of the samples for the years 1993 to 2001, but only in seven and five out of the ten studied samples for each of the years 1991 and 1992, respectively. Our study shows that genomic DNA is stable in dried blood stored on filter paper at ambient tropical conditions for at least 11 years. However, DNA quality for amplification of larger DNA fragments decreased when the specimens were stored for longer than 10 years.