The evaluation of stability of blood stains immobilized on the FHA cards during their prolonged storage

: We have studied the samples of dry blood immobilized on the FTA cards following a 15-year period of their storage at room temperature. The DNA preparations were obtained based on the protocol recommended by the manufacturer including washing up with the FTA reactant and in parallel by means of complete extraction with the use of robotic stations. The preparations were compared in terms of the content of amplificationally active DNA and the effectiveness of typing STR-loci of chromosomal DNA. The complete genetic profile was derived only from 41 (82%) of the 50 FTA cards with immobilized blood samples available for the investigation that had been treated with the FTA reactant and stored during 15 years at room temperature. In 9 (18%) cases, incomplete genetic profiles were obtained that were characterized by the absence of PCR-products, as well as missing of true alleles and the presence of pseudoalleles. Such poor results are supposed to be attributable to the occurrence of the residual inhibitors of DNA-polymerase activity due to the incomplete purification of the samples. This disadvantage was overcome by the application of robotic stations for the total DNA extraction. This approach made it possible to obtain the acceptable genetic profiles for each blood samples stored at the FTA cards during 15 years. Nevertheless, even these preparations exhibited the reduced matrix activity of high molecular weight SRT-loci. This observation suggests that long-term storage of dry blood samples on FTA cards at room temperature does not guarantee the absence of degradation of their DNA.