[Comparative research of the influence factors of DNA extraction of bloodstain on the filter paper with Chelex-100 method].

To improve DNA extraction from bloodstain on the filter paper and to establish a rapid, simple, and cost-effective method for DNA extraction suitable for database construction. Seven hundred and fifty two aged bloodstains on filter paper were randomly divided into four groups. The four different DNA extraction methods were compared with each other, and two DNA extraction methods used for 63 fresh bloodstains on filter paper were also compared with each other. There were no statistically significant differences observed among the four DNA extraction methods (P > 0.05) for aged bloodstains on filter paper; But the difference between the two DNA extraction methods for fresh bloodstains on filter paper was obviously (P < 0.05). Extraction of DNA samples from aged bloodstains on filter paper can be accomplished by using Chlex-100 methodology directly with no need to wash the bloodstains.