[Comparison of Three Drowning‑related Plankton Testing Methods in Drowning Diagnosis].

Objectives: To compare the application effects of plankton multiplex polymerase chain reaction-capillary electrophoresis (PCR-CE), SYBR Green Ⅰ real-time quantitative PCR (qPCR) and microwave digestion-vacuum filtration-automated scanning electron microscopy (MD-VF-Auto SEM) in the diagnosis of drowning.

Methods: Lung, liver and kidney tissues from 212 drowned corpses and 30 non-drowned corpses were examined respectively by the three drowning-related plankton testing methods, and the detection rates of plankton in each tissue by three methods were compared.

Results: In drowned corpses, the total detection rates of PCR-CE, qPCR, and MD-VF-Auto SEM were 93.9%, 96.2%, and 95.3%, respectively, with no statistically significant difference (P>0.05). The detection rate of lung tissue by MD-VF-Auto SEM (100%) was higher than those of PCR-CE and qPCR (P<0.05), and there was no significant difference in the detection rates of the three methods in liver or kidney tissues (P>0.05). In non-drowning corpses, a small number of diatoms (less than 10 cells/10 g) were detected by MD-VF-Auto SEM method, only in liver and kidney tissues, while the other two methods yielded negative results for all tissues.

Conclusions: All three methods have good efficacy in the examination of drowned corpses. The MD-VF-Auto SEM method directly observes diatom morphological characteristics through scanning electron microscopy, and the qualitative and quantitative analyses are intuitive and accurate. It has great advantages in the examination of difficult degradation samples. The PCR-CE method and qPCR method have a low sample demand (0.5 g), are easy to operate and have short detection time (4-7 h). They are easy to be applied in the grassroots departments and are suitable for the rapid determination of drowned corpses in routin cases. The combination of the two DNA methods with the MD-VF-Auto SEM method can increase the detection rate of plankton, ensuring the reliability of examination results. This combined use is of significant importance in the application of drowning diagnosis.