Stability of postmortem methemoglobin: Artifactual changes caused by storage conditions

• Published in: Forensic science international 2018-02, Vol.283, p.21-28
• Main Authors: Varlet, Vincent, Ryser, Elenore, Augsburger, Marc, Palmiere, Cristian
• Format: Article
• Language: English
• Subjects: Anoxia; Autopsies; Autopsy; Autoxidation; Biological activity; Cocaine; Cryoprotectors; Cytochrome; Delay; Erythrocytes; Ethylenediaminetetraacetic acids; Forensic sciences; Hemoglobin; Legal medicine; Methemoglobin; Methemoglobinemia; Microbial activity; Microorganisms; Optical measurement; Oxidation; Oxidizing agents; Poisoning; Postmortem; Reductase; Refrigeration; Storage; Storage conditions
• ISSN: 0379-0738; 1872-6283
• DOI: 10.1016/j.forsciint.2017.12.009

•We monitored methemoglobin changes in blood samples during storage.•Different temperatures and preservatives have been tested on cardiac and peripheral blood.•Different post-mortem intervals and storage time have been studied.•For short storages, blood samples taken at autopsy should be refrigerated and stored in EDTA preservative.•For longer storages, blood taken at autopsy should be should be frozen with cryoprotectant at −80°C. Hemoglobin is the protein in red blood cells that carries and distributes oxygen to the body. Methemoglobinemia is a blood disorder in which an abnormal amount of methemoglobin (MetHb), a form of hemoglobin (Hb), is produced from either inadequate MetHb reductase activity or too much MetHb production or by exposure to oxidizing agents. This could lead to anoxia and death if it is not treated. However, this parameter has not been investigated as a valid post-mortem indicator because random MetHb levels have been observed in various studies: MetHb increases can be observed due to autoxidation during storage, and MetHb decreases can be observed due to MetHb reductase or microbial activity in post-mortem samples. MetHb variations can also come from the blood state and can interfere in the optical measurements of MetHb. We have studied the post-mortem MetHb concentrations according to various storage conditions. Based on our results, both the post-mortem delay and the delay before analysis should be reduced whenever possible to avoid changes in MetHb. If the analysis is delayed for a short period of time (two weeks), the blood sample taken at autopsy should not be frozen but collected in EDTA preservative and stored under refrigeration (4–6°C) until analysis. If the analysis is delayed for a longer period (more than two weeks), the blood sample should be frozen with cryoprotectant at −80°C or −196°C.