Evaluation of the methods used for carboxyhemoglobin analysis in postmortem blood

Numerous methods have been described in the literature for the determination of carboxyhemoglobin (COHb) in whole blood. The most popular and widely used have been (1) the spectrophotometric methods, which could be performed either by using a conventional spectrophotometer or by using specialized automated instruments known as CO-oximeters; (2) the gas chromatographic methods, with variable detection systems, which have been considered as the reference methods for every carbon monoxide analysis. The authors have critically reviewed previously reported comparative studies on these methods, considering statistical and analytical matters, in order to propose the best method for the determination of COHb in postmortem blood, that could be utilized in forensic toxicology laboratories where such analyses are limited in number (less than 20 per year). Criteria for evaluation have been accuracy, reliability, simplicity, time, and cost. The authors' concluding statement has been that the manual spectrophotometric method could be the method of choice for COHb determination in postmortem blood samples. It is simple, rapid, and reliable and fulfills the forensically acceptable accuracy. It is performed by the use of a conventional spectrophotometer, which is considered a basic instrument in every analytical laboratory.