Abstract
PurposeAn inter-method variation experiment to evaluate visible spectrophotometric methods for determining carboxyhemoglobin (CO-Hb) in blood was performed in 17 different forensic science laboratories.MethodsThree reference samples were prepared and the actual percentages of CO-Hb (%CO-Hb) in reference samples were determined with gas chromatography. The %CO-Hb values in reference samples were measured via four procedures: (1) the “Standard method of chemical analysis in poisoning 2017” (edited by the Pharmaceutical Society of Japan), (2) the isosbestic point method (developed by the Department of Forensic Medicine, Kagawa University), (3) the alkaline condition method, and (4) ISO 27368 with a slight modification.ResultsProcedures (1) and (2) gave results approximately the same as the actual values in low-%CO-Hb samples, but both methods underestimated %CO-Hb levels in blood samples with high %CO-Hb. Using a formula reported by Katsumata et al., procedure (3) overestimated %CO-Hb levels in blood samples with low %CO-Hb, while using the modified formula, gave underestimates in all samples. Procedure (4) gave %CO-Hb values relatively close to the actual values. Thus, an accuracy evaluation test was performed for this procedure and the values obtained were close to the actual CO-Hb content levels.ConclusionsProcedure (4) was considered sufficiently accurate and thus recommendable for use in forensic science laboratories.
Highlights
Many poisoning accidents caused by carbon monoxide (CO) have occurred in Japan, and a total of 2008 accidents were reported to the National Research Institute of Police Science (NRIPS) in 2016 [1]
We calculated the square of the difference between the CO-Hb content measured spectrophotometrically and the CO-Hb content determined using gas chromatography (GC) (Table 1)
Because the values obtained by procedure (4) were more accurate than those obtained by the other procedures, we attempted to perform the test again to confirm the accuracy
Summary
The relative concentration of CO-Hb to whole hemoglobin (CO-Hb saturation; %CO-Hb) is measured to estimate the degree of CO toxicosis. Many spectrophotometric methods have been reported for measuring %CO-Hb, including measurements of absorption at the Soret band [6, 7], measurements of absorption at the α and β bands in the presence of a reducing agent [8,9,10,11,12], and the use of commercially available oximeters [13, 14]. Methods based on measuring the difference in the visible spectrum (α and β band) between Hb and CO-Hb in the presence of a reducing agent are mainly used in forensic science laboratories in Japan
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