Diatom test has been a significant tool for the diagnosis of drowning. The reliability of the diatom test is still in strong dispute in the field of forensic science because of the false-positive results. This study was designed to quantitatively compare the numbers of the diatoms in false-positive cases and true drowning cases. Diatom samples from 64 victims were used in this study: 32 cases are confirmed drowning victims and other 32 cases died from non-drowned death. Samples were subject for the diatom test those were analyzed by the microwave digestion-vacuum filtration-automated scanning electron microscopy method (MD-VF-Auto SEM method) that we developed before. The results did show that there are false-positive diatoms detected in the liver and kidney tissues of non-drowned bodies: 6/20 in liver tissues and 7/20 in kidney tissues. However, the quantitative studies showed that there are statistical differences with the numbers of diatoms in the false-positive cases and in the true drowning cases. Diatom test of single organ is difficult for us to distinguish the sources of the diatoms detected. Therefore, comprehensive analysis of multiple organs would be more useful for the diagnosis of drowning.
Keywords: Diatom test; Drowning; False positive; Forensic pathology.