Discussion
Analytical Performance
The analyzers exhibited reasonable performance at measuring vaporous ethanol reference standards in vitro, especially considering the low-cost of the devices. In the United States, the National Highway Traffic Safety Administration (NHTSA) offers performance recommendations for alcohol screening devices (ASDs) \cite{NationalHighwayTrafficSafetyAdministration2008}. For ASDs, the total allowable error at the 0.020 g/210L concentration is ± 60% at the 95% coverage interval. The analyzers examined in this study met this performance requirement, showing a total error of ≤ 15% at the 0.020 g/210L concentration, although they are not listed on the NHTSA's conforming products list of ASDs \cite{2012}.
For in vivo
use, manufacturers of the instruments should consider programing the
instrument for a duplicate breath test sequence, reporting the mean of
the two measurements, along with the associated uncertainty. An
uncertainty function could be built into the software of the smartphone
app to provide users with additional information about the uncertainty
of the measurements obtained \cite{Gullberg_2011}. In addition, calibration reports could be recorded by the smartphone app
and notify the user when recalibration is needed. In the final analysis, the performance requirements for breath alcohol analyzers is up to the end user’s tolerance for uncertainty.
Potential Interfering
Substances
Potential interfering substances are volatile organic substances other
than ethanol on a person’s breath which have the potential to interfere
with the accurate analysis of vaporous ethanol \cite{Gullberg1994,Jones1996,Jones1989,Jones2008a}. These substances have an impairing affect similar to or greater than that found with ethanol \cite{Caldwell1997-in,Cowan1990-xl}. Normally, potential interfering
substances are found in such low concentrations that they are unlikely
to interfere with an ethanol breath test \cite{Flores1985a}.
However, there are some circumstances in which interfering substances
may be present in high enough concentrations that they may falsely
elevate an ethanol breath test \cite{Caravati2010,Jones2007,Norfolk1997}.
Acetone
Acetone has been found in the breath of people with diabetes, during
times of fasting, and in very low carbohydrate dieters \cite{Ruzsanyi2017}. Electrochemical fuel cell breath alcohol analyzers are
known to be unaffected by acetone \cite{Falkensson1989}.
The analyzers examined in this study use a fuel cell and
did not respond to acetone.
Isopropanol
The analyzers showed an apparent ethanol response to isopropanol.
Isopropanol may be present in elevated concentrations on a person’s
breath after drinking denatured alcohol \cite{Jones1989a} or produced endogenously from the biotransformation of
acetone to isopropanol \cite{Jones2015}. In one case
study, a self-reported teetotaler obtained a false positive result on an
electrochemical fuel cell breath alcohol analyzer after following a very
low carbohydrate ketogenic diet \cite{Jones2007}. In
another study, isopropanol in the breath was found to be elevated after
eating a ketogenic meal \cite{Li2017}. Users
engaged in very low carbohydrate ketogenic dieting should be aware of
the possibility of obtaining elevated BrAC results based on their diet.
Methanol
Methanol may be present in elevated concentrations on a person’s breath
after consuming large amounts of fruit \cite{Lindinger1997}, in alcoholics \cite{Wigmore2008,Jones1988}, or through accidental exposure due to the improper
production of distilled spirits \cite{Kane1968,Paasma2007}. There are two unfortunate cases
reported in the literature where a breath alcohol analyzer mistook
methanol for ethanol, delaying medical treatment, resulting in the
subjects dying from methanol poisoning \cite{Jones1989}. The
analyzers examined responded to methanol. Users should be
aware of the potential, but the unlikely possibility of elevated BrAC
results due to methanol.
Limitations
Vaporous ethanol reference material produced by breath simulators cannot
account for the complex physiologic gas exchange taking place in the
lungs and airways of live subjects \cite{Jones1990,King2013,Gullberg1990,Anderson2003,Lubkin1996}, nor the heterogenous nature of breath alcohol produced during a single exhalation \cite{Vosk2014}. The SD of measurements from live
subjects has been shown to be greater than the SD produced by breath
simulators \cite{Gullberg1989}. Fuel cell breath alcohol
analyzers need to be recalibrated periodically, and the longevity of the
analyzers was not examined in this study. An important consideration for
those wishing to use these instruments is that the instruments must be
sent back to the manufacturer regularly for recalibration. Individuals or institutions using these instruments may need to keep several
on hand while periodic
recalibrations are performed. Regular users of these instruments should incorporate quality assurances practices to
ensure the accuracy of the results meets the requirements of the
intended use. Researchers should acknowledge the limitations of the instruments, as well as perform accuracy checks to ensure the analytical performance falls within the necessary limits required by the investigation \cite{Dubowski1994}.
Conclusion
The breath alcohol analyzers
examined in this study showed reasonable ability to measure vaporous
ethanol, especially at or below concentrations of 0.080 g/210L. At the
0.080 g/210L ethanol vapor concentration, the combined expanded
measurement uncertainty was ≤ ± 0.013 g/210L at the 95% coverage
interval for all instruments. The likelihood of false readings from
potential interfering substances appears to be small but may be a
concern for those engaged in ketogenic diets with elevated levels of
isopropanol. The analyzers offer a rapid, cost-effective way to
measure BrAC. Applications for potential use
include drinking establishments, health care, family law, remote
monitoring, personal use, research, and workplace testing. Finally, the
accuracy and precision of personal breath alcohol analyzers must be
evaluated against the intended use of the instrument.