Stability of Carboxyhaemoglobin in Blood Samples at Different Periods and Temperatures: A Forensic and Toxicological Tool for Diagnosis

Carbon monoxide (CO) is one of the most toxic agents in clinical and forensic practices. Diagnosis of CO poisoning is a challenging task and needs a high level of suspicion. Carboxyhaemoglobin (COHb) level is considered the only established marker for diagnosis. The current work aims to determine the levels of COHb in blood samples collected from CO poisoned patients on admission and to re-estimate those levels after storage of samples for different periods and after incubation at various temperatures. The results showed that the mean concentrations of carboxyhaemoglobin at time of admission=23.05 ± 13.44. Levels demonstrated insignificant change after either refrigerated storage of samples for different periods (one, two and three years) or after their incubation at different temperatures (37°C, 40°C and 50°C). It can be concluded that COHb concentration remains stable in refrigerated stored blood samples for up to 3 years as well as those present in high temperatures. It is recommended to immediately collect and store blood samples from patients suspicious of CO poisoning. When CO oximetry is not available, samples could be transported and sent to outside laboratory for analysis even after a long time has been passed. This could have great toxicological and medicolegal implications in cases of CO poisoning whether intentional or due to accidents and fires.