Reliable and accurate data, of the consequences of drinking on the driver and other road users, is therefore necessary. In addition, lack of defined time interval between accident and collection of blood samples for analysis or breath testing or making subjective assessment render the determined BAC values inappropriate, since blood alcohol concentration diminishes as alcohol is progressively eliminated from the blood with time after ingestion. Subject Selection A number of selection factors may affect the determination of the true prevalence of alcohol involvement. Not every RTA victim is tested for alcohol, and more-over, the criteria for selection is often not clearly stated. For instance, due to a number of reasons, such as refusals and severity of injury, completeness of information about alcohol involvement in non-fatal subjects is less likely than in fatal victims.
Men are also more likely to be selected for blood alcohol determination at autopsy than women.
While the age bracket of those tested may not be specified, comparatively large numbers of adolescents and young adults are more likely to be included, and therefore appear to comprise the majority of those intoxicated. In accident data derived from police records, those perceived to be responsible for the accident are more likely to be evaluated. Drivers involved in fatal RTAs, for example, are more likely to have blood alcohol determined than passengers, pedestrians or cyclists. Without a clear statement of inclusion and exclusion criteria, the representativeness of the subjects tested cannot be ascertained, consequently the BAC results may not be generalizable to all casualties involved. In view of these inconsistencies, caution is needed while interpreting blood alcohol data from different studies.