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For the preservation of tissue samples, formalin fixation followed by paraffin embedding (FFPE) has been the method of choice for decades, mainly because it maintains the morphologic characteristics of the original tissue particularly preserved, as well as its genetic material. FFPE cells can be used to perform molecular tests, such as conventional (c) or quantitative (q) reverse transcriptase polymerase chain reaction (RT-PCR), in retrospective investigations. However, extracting RNA from archived FFPE tissues is a challenging procedure, as it requires time and the use of complex extraction methods. As specific FFPE extraction methods are not always available in the laboratories, the objective of this study was to evaluate the performance of a method based on phenol-chloroform (PC) and 2 commercial methods for RNA extraction, adapting their protocols for FFPE tissues. For this study, a pool of FFPE tissues underwent RNA extraction by PC, QIAmp Viral RNA Mini, and RNeasy Mini Kit. Both the RT-cPCR and the RT-qPCR results were favorable, demonstrating the viability of the RNA. As these results expanded the alternatives for low-budget FFPE extraction, the choice of the ideal method to be used will depend on the availability of reagents and kits.

OBJECTIVE To evaluate the performance of post mortem laboratory analysis in identifying the causes of hemorrhagic fever and/or neuroinvasive disease in deaths by arbovirus infection. METHODS Retrospective cross-sectional study based on the differential analysis and final outcome obtained in patients whose samples underwent laboratory testing for arboviruses at the Pathology Center of the Adolfo Lutz Institute, in São Paulo, Brazil. RESULTS Of the 1355 adults clinically diagnosed with hemorrhagic fever and/or neuroinvasive disease, the most commonly attributed cause of death and the most common final outcome was dengue fever. Almost half of the samples tested negative on all laboratory tests conducted. CONCLUSION The failure to identify the causative agent in a great number of cases highlights a gap in the diagnosis of deaths of unknown etiology. Additional immunohistochemical and molecular assessments need to be added to the post-mortem protocol if all laboratory evaluations performed fail to identify a causative agent. While part of our findings may be due to technical issues related to sample fixation, better information availability when making the initial diagnosis is crucial. Including molecular approaches might lead to a significant advancement in diagnostic accuracy.