Effect of alcohol swabbing of venepuncture site on blood alcohol estimation: A literature review

Estimation of blood alcohol concentration is one of the very important investigations in medico-legal cases dealing with drink and driving, alcohol toxicity etc. There are many factors which may influence estimation of blood alcohol concentration of an individual. One of these factors is thought to be application of alcohol containing swab at venepuncture site, prior to collection of blood for alcohol estimation, either by gas chromatography or by enzymatic assay. Alcohol content of swab, either plain ethanol or iso-propyl alcohol, is said to influence blood alcohol estimation, to a significant extent, is a very common information rather misinformation given to all medical practitioners worldwide. Unfortunately, Courts of Law, in India also have to believe on this, and in many cases defence try to create benefit of doubt, using this information. It is commonly learnt and taught to Medical graduates, that while collecting blood samples from an individual for Blood Alcohol estimation, spirit swab should not be used for cleaning area of venepuncture. This is due to reason believed so far, that alcohol swabbing of venepuncture site can alter Blood Alcohol Estimation significantly. However there is no any study advocating this theory. Moreover review of literature pertaining to this subject has shown studies, which tend to prove that this concept is nothing but a myth and one has to be very particular to prove alteration in blood alcohol concentration due to alcohol swabbing of venepuncture site. Secondly, the literature and curricular statements in Forensic Medicine, which is written long back, needs exhaustive changes, and should be more evidence based.