Human background DNA on stones in an urban environment

Stones are frequently used as tools in criminal acts. In our department, around 5 % of all analysed crime scene related trace samples are contact or touch DNA traces swabbed from stones. These samples are primarily related to cases of damage to property and burglary. In court, questions can arise about DNA transfer and the persistence of background DNA not related to the respective crime. To shed some light on the question of how likely it is to detect human DNA as background DNA on stones from an urban environment, the surfaces of 108 stones sampled throughout the city of Bern, the Swiss capital, were swabbed. We detected a median quantity of 33 pg on the sampled stones. STR-profiles suitable for a CODIS (Combined DNA Index System) registration in the Swiss DNA database were established from 6.5 % of all sampled stone surfaces. For comparison, retrospective casework data analysis from routine crime scene samples demonstrates a success rate of 20.6 % for the establishment of CODIS-suitable DNA profiles from stones sampled for touch DNA. We further investigated how climatic conditions, location and properties of the stones affected the quantity and quality of the recovered DNA. In this study, we show that the quantity of the measurable DNA decreases significantly with increasing temperature. Furthermore, less DNA could be recovered from porous stones, compared to smooth ones.     

“萤火虫”成像技术联合声触诊组织量化技术在甲状腺结节诊断中的应用价值

目的探讨"萤火虫"成像(MicroPure)技术联合声触诊组织量化(VTQ)技术在甲状腺结节诊断中的应用价值。方法 72例患者(共78个甲状腺结节)术前分别行常规超声、MicroPure及VTQ技术检查,以病理结果为金标准,分别计算MicroPure技术、VTQ技术及两者联合应用诊断甲状腺恶性结节的敏感性、特异性、准确性、阳性预测值及阴性预测值。结果 MicroPure技术对甲状腺结节内部微钙化的显示率较常规超声高,差异有统计学意义(P=0.008)。应用MicroPure技术、VTQ技术及两者联合诊断甲状腺恶性结节的敏感性分别为67.9%、82.1%及89.3%,特异性分别为86.0%、68.0%及68.0%,准确率分别为79.5%、73.1%及75.6%,阳性预测值分别为73.1%、59.0%及61.0%,阴性预测值分别为82.7%、87.2%及91.9%。结论 MicroPure联合VTQ技术在甲状腺结节鉴别诊断中具有较高的临床应用价值。