PCR DNA typing of stamps: evaluation of the DNA extraction.

Today, the PCR analysis of DNA from the saliva deposited on a stamp of an anonymous letter can lead to an identification. However, this analysis still involves problems, and DNA extraction can be particularly difficult. A comparative study of two DNA extraction methods with two categories of postage stamps was carried out and a purification process was tested. This study shows that the extraction with phenol/chloroform gives much better results than Chelex extraction. A purification process such as the use of Centricon 100 microconcentrators is recommended when an inhibition of PCR is present. This operation, however, results in a large loss of material.