1. ¹Department of Forensic Chemistry, National Board of Forensic Medicine and University Hospital, Linköping, Sweden
2. ²Department of Obesity Research, Karolinska Hospital, Stockholm, Sweden

Correspondence: Dr AW Jones, Department of Forensic Chemistry, National Board of Forensic Medicine and University Hospital, Artillerigatan 12, Linköping 581 33, Sweden. E-mail: wayne.jones@RMV.SE

Received 18 May 2006; Revised 31 May 2006; Accepted 2 June 2006; Published online 8 August 2006.

Abstract

A 59-year-old man undergoing weight loss with very low calorie diets (VLCD) attempted to drive a car, which was fitted with an alcohol ignition interlock device, but the vehicle failed to start. Because the man was a teetotaller, he was surprised and upset by this result. VLCD treatment leads to ketonemia with high concentrations of acetone, acetoacetate and -hydroxybutyrate in the blood. The interlock device determines alcohol (ethanol) in breath by electrochemical oxidation, but acetone does not undergo oxidation with this detector. However, under certain circumstances acetone is reduced in the body to isopropanol by hepatic alcohol dehydrogenase (ADH). The ignition interlock device responds to other alcohols (e.g. methanol, n-propanol and isopropanol), which therefore explains the false-positive result. This 'side effect' of ketogenic diets needs further discussion by authorities when people engaged in safety-sensitive work (e.g. bus drivers and airline pilots) submit to random breath-alcohol tests.