The relationship between blood and urine alcohol concentrations at autopsy.

The relationship between the blood alcohol concentration and the urine alcohol concentration was studied in 109 routine coroner's autopsies. Although the average ratio for urine alcohol concentration to blood alcohol concentration lay close to the ratio of 4:3 quoted in the literature, the actual ratios determined were widely scattered around this value. Thus the use of this simple ratio to estimate the blood alcohol concentration from the urine alcohol concentration at post-mortem was unreliable. An equation determined by employing linear regression analysis was similarly unhelpful in enabling one to derive a precise value for the blood alcohol concentration from a given urine alcohol concentration. It was concluded that the main value in determining the urine alcohol concentration at autopsy was to exclude the possibility of the alcohol present in the blood sample having been generated during the post-mortem interval.