therefore to consider the consequences of ketogenic diets
when blood- and breath-alcohol tests are interpreted in a
legal context.
Suspected drunk drivers first submit to a roadside breathalcohol
screening test and if this is positive they provide
either an evidential breath-alcohol test or a blood specimen
is taken for laboratory analysis. Breath-alcohol screening
tests incorporate electrochemical detectors similar to those
used in the ignition interlock device and therefore respond
to isopropanol. By contrast, most evidential breath-testing is
performed by multifilter infrared analysis and these are
programmed to abort the test if acetone is detected on the
suspect’s breath above a certain threshold value.10 Because
the half-life of isopropanol (t12
¼3–5 h) is much shorter than
that of acetone (t12
¼15–25 h), it is hard to envisage finding
elevated concentrations of isopropanol without concomitant
high concentrations of acetone. However, evidential
breath-alcohol analyzers based on electrochemical oxidation
cannot distinguish ethanol from isopropanol and this
resulted in a false-positive test after VLCD. An apparent
BAC of 0.02 g/100 ml seems likely according to the present
case report.
The reduction of acetone to isopropanol is not a problem
with blood-ethanol determination because gas chromatography
is used and this highly specific method can resolve
ethanol from both acetone and isopropanol under normal
operating conditions.15
In conclusion, we suggest that people on ketogenic diets
run the risk of false-positive breath alcohol tests owing to
reduction of acetone to isopropanol. People on VLCD need
to be warned about this artifact when alcohol ignition
interlock devices are used. This possibility also warrants
consideration in connection with workplace alcohol testing
and screening of drunk drivers with electrochemical sensors.
Both the manufacturers of ignition interlock devices and
government agencies that monitor performance and administer
sanctions should consider these problem. Technological
improvements might be possible, for example, by measuring
not only the final reading but also the kinetics of the
detector response to different alcohols.
Acknowledgements
There was no external funding for preparing this article and
neither author considers there to be any conflicts of interest.