Estimating a reliable cutoff point of 1-propanol in postmortem blood as marker of microbial ethanol production

Abstract

The interpretation of the ethanol analysis results in postmortem cases may be challenging when the origin of postmortem ethanol (antemortem ingestion or microbial production) is under dispute. In this study, we investigated the suitability of blood 1-propanol cutoff concentration as a reliable marker for the discrimination between “positive” and “negative” for postmortem ethanol production (PEP) autopsy blood samples by performing receiver operating characteristic (ROC) analysis. The results indicated that a threshold 1-propanol concentration of 0.104 mg/dL had an area under the curve of 0.90 (standard deviation = 0.03), sensitivity of 79%, and specificity of 91% for predicting PEP with 95% confidence interval. This means that the positive for PEP autopsy blood samples yield significantly differentiated PEP than approximately 90% of the controls. The estimated concentration of 1-propanol is an applicable threshold (cutoff) value for autopsy blood 1-propanol to discriminate between “positive” and “negative” samples for PEP. We named this threshold 1-propanol concentration (of 0.104 mg/dL) as “1-propanol criterion.” In an effort to test its applicability to postmortem cases, we evaluated blood ethanol and 1-propanol from 222 postmortem cases records. The results showed that 10% of the tested samples were positive for PEP, and only a few of them were from bodies with signs of putrefaction at autopsy. This finding indicates that PEP in a corpse could take place before the appearance of obvious putrefaction. We suggest the ROC-based calculation of the 1-propanol cutoff concentration, at 0.104 mg/dL, as an effective method for “flagging” blood samples as positive for PEP irrespectively of the presence or not of putrefaction.