Journal of Analytical Toxicology, Vol. 26, September2002
Reference Limits for Urine/Blood Ratios of Ethanol in
Two SuccessiveVoids from Drinking Drivers
A.W. Jones
Department of Forensic Toxicology, University Hospital, 581 85 Link6ping, Sweden
Abstract[
Specimens of venous whole blood and two successive urinary voids
were collected from 450 individuals apprehended for driving under
the influence of alcohol in Sweden. The first specimen of urine
(UAC-1) was obtained as soon as possible after arrest, and the
second void (UAC-2) was collected about 60 rain later (mean 66
rain, range 30-130). A specimen of venous blood was drawn
approximately 30 rain after the first urine sample was collected.
Ethanol was determined in blood and urine by headspace gas
chromatography, a method with high analytical precision
(coefficient of variation -1%). The mean UAC for the first void was
2.60 g/L (range 0.21-5.35) compared with 2.40 g/L (range
0.16-5.50) in the second void. The mean concentration of alcohol in
venous blood (BAC) was 1.97 g/L (range 0.08-4.57). The
concentrations of ethanol in the two voids of urine were highly
correlated (r -- 0.97, residual standard deviation [SD] 0.22 g/L). The
UAC and BAC results were also highly correlated; r = 0.958
(residual SD 0.28 g/L) for the first void and r = 0.978 (residual SD
0.21 g/L) for the second void. The concentration of ethanol in the
first void (UAC-1) was higher than the second void (UAC-2) in 383
(87%) instances, decreasing by 0.23 g/Uh on average. In 57
instances (13%), UAC-1 was less or equal to UAC-2 with a mean
increase of 0.19 g/L. When BAC exceeded 0.5 g/L (N -- 429), the
mean UAC-1/BAC ratio was 1.345 with 95 % reference limits of
0.968 and 1.72, which agreed well with median (2.5th and 97.5th
percentiles) of 1.325 (0.938 and 1.79). For the second void, the
mean UAC-2/BAC ratio was 1.221 with 95% reference limits of
0.988 and 1.45 and with a median (2.5th and 97.5th percentiles)
of 1.226 (0.997 and 1.46). These reference limits are appropriate
to use when a person's venous BAC needs to be estimated with
reasonable scientific certainty from the concentration determined
in specimens of urine.
Introduction
Many review articles and books dealing with forensic aspects
of ethanol mention that the average ratio of ethanol concentrations in urine and blood (UAC/BAC)is 1.3:1 (1-3). When the
British government introduced their 1967 Road Safety Act, a
blood-alcohol concentration (BAC)of 80 rag/100 mL (0.08 g%)
was considered as equivalent to a urine-alcohol concentration
(UAC) of 107 rag/100 mL (0.107 g%), which suggests a
UAC/BACratio of 107/80 or 1.33:1 (4). This kind of legislation
avoids the need to discuss variability in the UAC/BACrelationship for any individual suspect and a similar approach was followed when statutory breath-alcohol limits were introduced in
the U.K. (35 ]~g/100mL). In many U.S. states, threshold alcohol
limits for driving are set at a blood-alcohol concentration of
0.08 g/100 mL or a breath-alcohol concentration of 0.08 g/210
L (blood/breath ratio 2100:1). Scant attention was given to the
magnitude of variation in urine/blood and blood/breath ratios
of ethanol between and within subjects, and any temporal
changes during absorption, distribution, and elimination of
ethanol were seemingly ignored (5).
Several studies have shown that UAC/BACratios are often less
than unity during the absorption stage of ethanol kinetics and
increase to reach a value close to 1.3:1 during the early part of
the post-absorptive phase and increase further as BACdecreases
to approach zero (6-9). The UAC/BACratio also seems to depend on the concentration of ethanol in the samples with low
concentrations giving high ratios, and therefore the amount of
ethanol consumed needs consideration (7). The length of time
that urine is stored in the bladder before voiding is also an important consideration because ethanol is continuously being removed from the blood by metabolism, but no oxidation of
ethanol occurs in the bladder. This situation results in abnormally high UAC/BACratios being obtained for the first void.
Likewise, a failure to empty completely the bladder on micturition is another factor that can skew the UAC/BACratio for
the second void. The combined influences of many physiological and experimental variables means that whenever a measured UAC is translated into a presumed BAC, the result
obtained is subject to considerable uncertainty (10). The magnitude of uncertainty in the UAC/BACrelationship for two successive voids collected from a large number of individuals
suspected of drunk driving is the subject of this article.
The results of this study will prove useful for clinical and
forensic scientists whenever urine is the only specimen available for analysis of ethanol and when a request is made to interpret this information in terms of the person's likely BACand
impairment of performance and behavior.
Reproduction(photocopying)of editorialcontentof thisjournal is prohibitedwithoutpublisher'spermission.
33:]
Journal of Analytical Toxicology, Vol. 26, September2002
Materials and Methods
The blood and urine specimens used in this study were obtained from drinking drivers apprehended by the police in
Sweden. All specimens were sent for analysis to the National
Laboratory of Forensic Toxicology(Link~ping, Sweden). For the
purpose of this study, cases were selected for evaluation if two
successive urinary voids and a specimen of venous whole blood
were available. The main defense challenge in Sweden is alleged
consumption of alcohol after driving or after being involved in
a traffic accident (11). In these situations, the UAC/BACratio
and the change in UAC between two successive voids can furnish useful information to support or challenge this defense
tactic (11,12).
Drunk drivers in Sweden are apprehended in connection
with (i) police sobriety check points, (ii) "tips" provided by
other motorists who might have observed dangerous or erratic driving, (iii) after committing a moving traffic violation,
and (iv) involvement in a traffic accident. Conducting field sobriety tests prior to administrating a roadside breath-alcohol
screening test is not necessary in Sweden. If the preliminary
breath test is positive, the suspect is taken to a police station
where either an evidential breath-alcohol test is made or blood
and urine specimens are collected for forensic analysis. If the
driver is apprehended at the wheel and lacks the opportunity to
claim consumption of alcohol after driving, then urine specimens are unnecessary.
The times of collecting blood and urine could not be controlled exactly because of the different circumstances, such as
the need for hospital treatment after a crash or the location of
the traffic stop as well as other time elements. Police instructions require that the first urine void be taken as soon as possible after the driver is apprehended. The sample of venous
blood is drawn about 30-60 rain later when a physician or registered nurse arrives, and then the police attempt to secure a
second sample of urine. The suspect is asked to empty the
bladder completely on each void, and the total volume of urine
collected is recorded. The urination is closely monitored by
police to counteract attempts at specimen adulteration. A 10mL aliquot from the pool of urine is transferred into a plastic
tube containing NaF (100 rag) as preservative and then made
airtight with a screw-on cap. Venous blood is taken under
sterile conditions from an anticubital vein into Vacutainer
tubes containing NaF (100 rag) and potassium oxalate (20 mg)
as preservatives. Two tubes are filled in rapid succession.
The tubes of blood and both urine specimens together with
arrest forms are sent by express mail to the National Laboratory
of Forensic Toxicology. The information written on the specimen tubes is compared with similar information on the accompanying forms, and any discrepancies are noted. The
concentrations of ethanol in blood and urine are determined in
duplicate by headspace gas chromatography as described in
detail elsewhere (13). This method has a high analytical precision with a coefficient of variation of about 1%. Two technicians
work independently with different sets of equipment and make
duplicate determinations on blood and urine specimens. The
means of duplicates were used in the calculation of UAC/BAC
ratios, and the concentration units were grams per liter.
The whole material consisted of 450 driving under the influence of alcohol (DUI) cases and the mean and standard deviation as well as median and 2.5th and 97.5th percentiles were
used as estimates of central tendency and variability (14). The
association between two variables, UAC-1 and UAC-2, for example, and between UAC and BAC was established by correlation-regression analysis, and the residual standard deviation
(SD) indicates the random errors. Reference limits for the
UAC/BACratios in the first and second voidswere calculated as
mean _+(1.96 x SD) as well as by calculating the median and
2.5th and 97.5th percentiles. This latter method is independent
of the shape of the distribution and can therefore be applied to
variables that are not normally distributed (14,15). Confidence
intervals (95%) for the UAC/BACreference limits were calculated as described by Bland (14).
Results
The average time difference between collecting the two urine
voids was 66 rain (range 30 to 130 rain) and venous blood was
mostly taken 30-60 rain after the first urinary void. Table I gives
descriptive statistics for the whole material as well as selected
sub-sets depending on the various conditions shown. Because
the UAC/BAC ratios tended to increase as concentrations of
ethanol in blood decreased, those cases with BAC less than 0.50
g/L (n = 21) were omitted from the main statistical analysis.
Table I. Descriptive Statisticsfor Blood and Urine Alcohol Concentrationsand Urine-to-Blood Ratios of Alcohol in First
and SecondVoids from Apprehended Drinking Drivers in Sweden
Sub-groups
N
Mean (SD)
BAC g/L
All subjects
BAC > 0.50
BAC < 0.50
UAC-1 < UAC-2
UAC-I > UAC-2
UAC-1 > UAC-2
and BAC > 0.5 g/L
450
429
21
56
393
375
1.97 (0.82)
2.05 (0.75)
0.33 (0.11)
2.17 (0.88)
1.94 (0.80)
2.02 (0.74)
334
Mean (SD)
UAC-1 g/L
Mean (SD)
UAC-2 g/L
Mean (SD)
median
UAC-1/BAC
Mean (SD)
median
UAC-2/BAC
2.60 (0.98)
2.69 (0.89)
0.59 (0.19)
2.43 (1.12)
2.62 (0.95)
2.72 (0.87)
2.40 (1.0)
2.50 (0.91)
0.40 (0.15)
2.62 (1.12)
2.37 (0.97)
2.46 (0.89)
1.38 (0.50) 1.33
1.34 (0.19) 1.32
2.21 (2.11) 1.66
1.09 (0.18) 1.14
1.42 (0.52) 1.35
1.38 (0.16) 1.34
1.22 (0.19) 1.22
1.22 (0.12) 1.22
1.32 (0.70) 1.20
1.20 (0.12) 1.22
1.23 (0.19) 1.22
1.22 (0.11) 1.22
Journal of Analytical Toxicology, Vol. 26, September 2002
These probably reflect individuals who are approaching a zero
blood-alcohol concentration. Furthermore, reference limits for
UAC/BACratios were calculated separatelywhen UAC-1< UAC2 (n = 56), which might indicate that the absorption and distribution of alcohol in the body was incomplete.The remaining 429
cases were analysed in detail and used to determine reference
limits for UAC/BACratios in first and second voids (Table II).
A strong correlation (r = 0.973) was found between UAC-1
and UAC-2in all 450 DUI cases and the residual SD was 0.22 g/L
(Figure 1). The associations between UAC-1and BACand UAC2 and BAC are shown in Figure 2 as scatter plots. The correlation coefficients were highly significant (p < 0.001), and the
residual SDs were 0.28 g/L for the first void and 0.21 g/L for the
second void, indicating somewhat less random variation when
a fresh urine specimen was obtained for analysis (second void).
Figure 3 shows the UAC/BACratios plotted against the corresponding blood-alcohol concentration. A statistically significant negative correlation was found for the first void (r =
-0.44) but not for the second void (r = -0.074) where no trend
was evident. This indicates that the value of the UAC/BACratio
for freshly produced urine and provided that BAC is higher
than 0.5 g/L is independent of the person's blood-alcohol concentration.
6.O"
5.0-
., . "
r = 0.073
I
.... . - J
UAC-1 = 0.31 + 0,953 UAC-2 i
Resldu=so = o.=5 o/"
I
4.0-
i~
........
""
."""
3.0-
9
~.
2.0-
'"**~
9 :,~"
""
.,'
,e
."
o e-
.'""
.,
~
.
....
.,'"
Table II gives mean, median, standard deviation, 95% reference intervals, and 2.5th and 97.5th percentiles for UAC/BACratios for both the first and second voids (iV = 429). The most
likely UAC/BACratios for these drunk drivers are given by the
mean or median of the distributions, being 1.33 for first void
and 1.22 for the second void. These values could be used to gain
an idea of what the person's BAC might be with a probability of
50%. However, because of analytical and physiological variations instead of an average or median value being used to estimate BAC,the 95% reference limits might be preferred. These
limits were considerably narrower for the second void with
2.5% being above 1.45 and 2.5% below 0.988. Because of the
large sample size (N = 429), the 95% confidence intervals for
these reference limits are fairly narrow (TableII). Dividing UAC
in a second void by 1.47 (the upper confidence band) will give
a highly conservative estimate of the person's venous BAC.By
contrast, for a randomly collected first void, the UAC must be
dividedby 1.75 to achieve the same level of confidence in the estimated BAC.When only those cases with UAC-1 > UAC-2are
included (iV = 393), the mean and medians were about the
same although the 95% reference limits were much narrower
(data not shown). This stricter selection criteria probably eliminates all individuals that have not reached the post-absorptive
phase of ethanol kinetics.
According to Table I, the mean and median of the UAC/BAC
ratios agree well for the second void, and the histogram and cumulative frequency plot show a very good fit to a Gaussian distribution (Figure 4).
Discussion
"
Urine has a long history as a biological specimen for the
analysis
of alcohol and the results corroborate any clinical
3 1.0-t 4
.t.'
signs and symptoms of drunkenness as noted by Erik M.P.Widmark in 1914 (16). Interest in measuring ethanol in body fluids
0.0
9
,
.
,
.
.
,
.
9
0.0
1.0
2.0
3.0
4.0
5.0
6:0
for legal purposes accelerated in the 1930s when it was found
UAC
(g/L) (second
void)
that many traffic crashes and deaths on the highway were
F i g u r e 1. Scatter plot and regression analysis of urine-alcohol concencaused by drunk drivers (17,18). Evidence of drunkenness and
tration in first and second voids, where N = number of x-y pairs, r = corunfitness to drive was obtained by recording various signs and
relation coefficient, and the dotted lines running parallel with the
symptoms of intoxication along with the concentration of
regression line are the 95% prediction intervals (+ 1.96 x residual stanethanol in a specimen of urine (19). Urine and breath were the
dard deviation).
preferred specimen for forensic analysis of alcohol because obtaining blood raised the constitutional issue of
self-incrimination, whereas the urine a person
Table II. Reference Limits and 95% Confidence Intervals for UAC/BAC
voided and the breath exhaled were considRatios of Ethanol for First and Second Voids Collected from Apprehended
ered waste products voluntarily discarded
Drinking Drivers with BAC > 0.5 g/L*
(17-19).
Over the past century, a vast literature has
Referencelimits
accumulated
on the UAC/BACrelationship in
UAC/BAC
and ( 9 5 %
UAC/BAC 2.5thand97.5th
specimens collected from both living and dead
Urine specimen mean(SD) CV% confidenceintervals) median
percentiles
subjects (20-25). In postmortem toxicology,
First void
1.345 (0.192) 14.3
0.968 (0.94-1.00)
1.325
0.938 and 1.79
the analysis and interpretation of ethanol con1.72 (1.68-1.75)
centrations measured in more than one body
Second void
1.221 (0.119)
9.7
0.988 (0.97-1.00)
1.226
0.997 and 1.46
fluid (blood and urine or blood and vitreous
1.45 (1.43-1.47)
humor) is virtually essential to boost confidence in the results (26). By contrast, in living
* N = 429. For comparisonnon-parametricmedianand 2.5th and 97.5th percentilesare given.
subjects, despite severe penalties and sanc...'~
9 .~."
.. "~*.
~'
.-"; * ,.";"d,
335
Journal of Analytical Toxicology, Vol. 26, September 2002
tions for DUI, the use of more than one body fluid for the determination of ethanol is extremely rare. The methods for measuring ethanol in urine are accurate and precise, and the
concentrations remain stable during long periods of storage at
4~ (27,28).
Some potential problems with the use of urine for the analysis of ethanol were dispelled when it was shown that neither
urine-creatinine, a biochemical marker for dilute specimens,
nor drinking water before voiding had any negative impact on
the UAC/BACrelationship (29,30).Another often cited criticism
of urine-ethanol measurements relates to the phenomenon of
urine retention, which has been suggested might lead to abnormally high UAC/BACratios (31). Although it is widely recognized that older men with prostrate enlargement have
difficulties emptying the bladder completely on each void, it is
also well-known that these individuals tend to urinate more frequently (32). Experiments are needed to establish the mean and
variation of UAC/BACratios in a well-characterized patient material made up of men and women with problems in emptying
the bladder completely on micturition. To the author's knowledge, these experiments have not yet been published.
It seems reasonable to assume that the concentration of
ethanol in any residual urine in the bladder, which was pro6.0
duced when the BAC was high becomes diluted with freshly
produced ureter urine that might contain a lower concentration of ethanol because of the metabolism of ethanol taking
place in the liver. When the BAC eventually reaches zero, the
residual urine in the bladder that might still contain ethanol
starts to become diluted with alcohol-free urine. Accordingly,
the first morning void after an evening'sdrinking could contain
ethanol reflecting the BAC prevailing during the night. But
the second morning void will be alcohol-free provided that the
BAChas reached zero at the time of the first morning void, and
one of the most urgent tasks on arising in the morning is to
visit the bathroom (33).
In the present large group of DUI suspects, the UAC/BACratios were somewhat higher for the first void (median 1.33),
compared with a second void (median 1.22). The residence
time of urine in the bladder before collecting the first void is
unknown but is probably longer than the mean of 66 rain before the second void was collected. During the production and
storage of urine in the bladder, a person's BAC does not remain
static but decreases by 0.10 to 0.25 g/L/h in the post-absorptive
state. The median UAC/BACratio of the second void was 1.22
probably representing freshly produced urine and a much
shorter storage time in the bladder. If the water content of
2.5
....
N=450
r= 0.958
UAC = 0.34 + 1.147 BAC
Residual SD = 0.28 g/L
g5.0
~'
~
j 9
.." 9 /
...
..'~" ~
.'"
...... "~:'4rL~../"
'~ 4,0
:"; 9 ~
2.0
"
9 ""
1.5
IN= 429
9
9
" • 9 99
[r = '-0.44
I UAC/BAC = 1.58- 0.113 BAC
~ ~ ;~ ..,.........
;...
.. .............
99 @i~ll,~J
9
........ ........
,' .L'~_,=.~
" - 9- i
o
-g 2.0
O
.... :
...~
,.o.......:S;;
3 0.0
. %.',
....
,,
9....
.,
9" "
First void
"~"
1.0
~0.5
i
"
0.0
,
2.0
,
0.0
9
,
oo
,
3.0
Blood alcohol (g/L)
4.0
510
1:o
2:0
3:o
4:o
Blood alcohol (g/L)
2.5"
~, 6.0.~
~ . ~.o-I
"B
~
/
"o 4.0-I
o
./'
. . : / /
. ~ .
...;,,J,.dl ...'
N=4~o
~ = o.~7o
UAC = o . o ~ , 1.10,AC
Residual SD = 0.21 g/L
."
0
I/
2.ol
O
J
..;,"
~ 10 1
" '" ; E" .
, ' ~ I ~ ' ~ ; ' . 9' ' '
'~:3 0 . 0 ~ S ' " " " "'"","
0.0
1.0
9
~' 2.0-
"~ 1.5-
,,,_. F T :."
",.''
....
O 1.0-
9
;;5;' ~;: .............................
I.~
......
~...~..~....p....p.,,.,....*.
...............
= ....................
,~0.5-
ISec~176
'
,
2.0
.
, .
3.0
Blood alcohol (g/L)
,
4.0
I
.
0.0
0.0
5.0
Figure 2. Scatter plots and regression analysis of urine-alcohol concentration against blood-alcohol concentration for first and second voids,
where N = number of x-y pairs, r = correlation coefficient, and the
dotted lines running parallel with the regression line are the 95% prediction intervals (__.1.96 x residual standard deviation).
336
.'.9'LL.....
~ ....... 9
",~_:i~.~l;Z,;.~. ' Z .
&
.."9
.
I N=429
I
r = -0.074
UAC/BAC = 1.24- 0.011 BAC
9
1'o
21o
31o
41o
s:o
Blood alcohol (g/L)
Figure 3. Scatter plots showing the relationship between urine/blood ratios of ethanol for first (upper frame) and second voids (lower frame) and
the underlying venous blood-ethanol concentration, where N = number
of x-y pairs, r = correlation coefficient, and the dotted lines running parallel with the regression line are the 95% prediction intervals (+ 1.96 x
residual standard deviation).
Journal of Analytical Toxicology, Vol. 26, September 2002
urine is taken as 100% (v/v) compared with 80-85% (v/v) for
whole blood,this gives a theoretical UAC/BACratio of 1.18:1 to
1.25:1 and these are the ratios expected if the urine was obtained by catheterization. After a period of continuous drinking,
especiallywith a rising BAC, the diuretic action of ethanol ensures that the person urinates frequently, so even the first void
from drunk drivers is a fair representation of the BAC existing
1-2 h earlier.
Dividing the UACof the first void by 1.33 gives an idea of the
average BAC during the time that the urine was being produced and stored in the bladder. Accordingly,the concentration
determined in the first urine sample collected after driving is a
good representation of the BAC at the time of driving. This
unique advantage of urine over other body fluids for forensic
analysis, namely to give an indication of the BAC at an earlier
point in time (i.e., the time of driving or crash), has surprisingly
not been fully appreciated. The person's BAC at the time of
200-1
15
o>,
u_
0.8 0.9
1.0
1.1
1.2 1.3
1.4 1.5 1.6 1.7 1.8
UAC/BAC (second void)
lool
,,o
/
'0t.
1
/. ,,
,ot
oO
o
'
0.8
oO"
/j
I
i
[
i
i
!
1.0
1.2
1.4
.
i
1.6
9
i
1.8
UAC/BAC (second void)
Figure 4. Frequency distribution (upper part) of urine/blood ratios of alcohol (N = 375) for the second urinary void when the BAC was above
0.5 g/L andwhen the concentration in first void (UAC-1)was higherthan
for the secondvoid (UAC-2). The lower plot shows UAs
ratiosas
a cumulativedistribution indicatinga good fit to a normal Gaussiancurve
with arrowsshowing median (50%)value of UAC/BACratio indicated.
driving is often a hotly debated issue in DUI litigation. If a
more conservative estimate of BACat time of driving is needed,
instead of dividing the UAC by the mean or median UAC/BAC
ratios of 1.33, an upper 97.5th percentile could be used instead (Table II). Such a calculation, with reasonable scientific
certainty, yields a minimum value for the person's BAC at the
time of driving. If a second urinary void is collected, dividing by
1.22 gives a good estimate of BAC during the period of collection of urine in the bladder and dividing by 1.47 gives a result
less than the true value with a probability of 40 to 1. The choice
between mean and median values as measures of central tendency and 95% reference limits derived from SD or 2.5th and
97.5th percentiles is somewhat arbitrary considering that the
distribution of UAC/BACratios, for the second void agreed well
with a Gaussian curve.
The first urinary void should never be discarded because the
ethanol concentration gives valuable information about the
person's BAC some time prior to obtaining the blood sample
such as at the time of driving. As recognized by Heise (23), this
is a unique advantage of urine over other body fluids used for
analysis of alcohol. Other strong advocatesof measuring alcohol
in urine were Biasotti and Valentine (31) who presented an excellent review of forensic aspects of UAC and variability in
UAC/BACratios. Their study and the conclusions therein deserve close attention from those interested in the use of urine
as a biological specimen for alcohol analysis in traffic law enforcement and forensic science.
Forensic toxicologists are often required to interpret the
concentrations of illicit drug in urine in relation to the time of
last use and occasionally also the amount taken or the likely
blood or plasma concentration (34). For drugs other than
ethanol, such questions are difficult or even impossible to answer with any degree of certainty. The physicochemical properties of ethanol and the high correlation between the
concentrations in blood and urine (Figure 2) are unlike those
of other drugs of abuse. The transfer of ethanol from blood to
urine occurs by passive diffusion, and the concentration in the
glomerular filtrate will mirror the concentration in plasma.
Ethanol shows negligible binding to plasma proteins and distributes evenly into the total body water, making it a lot easier
to interpret the concentration of ethanol in urine compared
with all other abused drugs (7,8,31).
The risk for post-sampling synthesis of ethanol should not be
overlooked when urine-ethanol concentrations are interpreted
(35,36). This problem can be avoided if the collection tubes contain at least 1% NaF and are stored in a refrigerator (+ 4~
pending analysis (37,38). These requirements are very important if information suggests that the donor was diabetic and
therefore prone to excrete sugar in urine and/or was suffering
from a urinary tract Candida infection (39). Without an enzyme
inhibitor, glucose in the urine together with viable yeast or
bacteria lead to production of ethanol if the samples are stored
at room temperature for at least 24 h (38). Whenever postsampling synthesis of ethanol is suspected, a control analysis
can be performed after allowing an aliquot to stand at room
temperature in a closed container for a few days (26). An appreciable increase in the concentration of ethanol above that expected from analytical imprecision alone is evidence for
337
Journal of Analytical Toxicology, Vol. 26, September 2002
on-going production of ethanol. However, absence of such an
increase is not proof that post-sampling synthesis of ethanol had
not already occurred earlier and all fermentable glucose converted before making the control analysis.
Herman Heise, a U.S. pioneer in use of chemical tests for alcohol influence (23) appreciated that the UAC/BACrelationship
could also be used to support or challenge alleged consumption
of alcohol after driving, which is a very common DUI defense
tactic (11,12). The BAC existing between two successive voids
can be estimated by dividing the UAC (second void) by a factor
of 1.33, the presumed population average urine/blood ratio of
ethanol. To avoid discussion and debate about a person's
urine/blood ratio of ethanol when making these conversions,
some jurisdictions have endorsed a threshold concentration of
ethanol in urine as a punishable offence,such as 107 mg/dL the
current legal limit in the U.K. In the state of Minnesota, a statutory UACof 0.1 g per 60 mL urine for a single void was taken as
being equivalent to a BAC of 0.1 g/100 mL and hence a UAC/
BAC ratio of 1.5:1 (100/60).
The results from this study, which involved the analysis of
blood and urine specimens from 450 individuals apprehended
for alcohol-impaired driving, have given reference limits for
the UAC/BACratios in first (random) and second urinary voids.
These limits are appropriate for use in civil and criminal litigation when UAC needs to be converted into the expected BAC
with reasonable scientific certainty. DividingUACby the 97.5th
percentile of the UAC/BACdistribution gives a conservative estimate of the person's actual BAC during the collection period
of urine in the bladder. The BAC obtained by this calculation,
with a probability of 40:1, will not exceed the true value. A
more conservative estimate can be obtained by use of the 99th
percentile of the UAC/BACdistribution ratio (data not shown).
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
Acknowledgment
This work was supported in part by funding from the National
Board of Forensic Medicine.
23.
24.
25.
References
1. R.N. Harger. Ethyl alcohol. In Toxicology, Mechanisms andAnalytical Methods, C.P. Stewart and A. Stolman, Eds.Academic Press,
New York, NY, 1961, pp 86-151.
2. R.N. Harger and R.B. Forney, St. Aliphatic alcohols. In Progress in
Chemical Toxicology, Vol. 3, A. Stolman, Ed. Academic Press,
New York, NY, 1967, pp 1-61.
3. J.C. Garriott. Medicolegal Aspects of Alcohol. Lawyers and Judges
Publishing, Tuscon, AZ, 1996.
4. Special Report, The Drinking Driver. British Medical Association,
London, U.K., 1965.
5. H.J. Walls and A.R. Brownlie. Drink, Drugs and Driving. Sweet and
Maxwell, London, U.K., 1985, pp 1-281.
6. M. Staak, E. Springer, and H. Baum. Vergleichende Untersuchungen ~ber den Aussagewert des HarnalkohoI-Blutalkoholquotienten unter experimentellen Bedingungen sowie im
Probenmaterial. Blutalkohol 13:100-120 (1967).
7. A.W. Jones. Ethanol distribution ratios between urine and capillary
338
26.
27.
28.
29.
30.
31.
blood in controlled experiments and in apprehended drinking
drivers. J. Forensic Sci. 37:21-34 (1992).
P. Zink and G. Reinhardt. Zur Theorie der,~thanolausscheidung im
menschlichen Urin. Blutalkohol 8:1-15 (1971 ).
S. Hishida, M. Kinoshita, I. Ijiri, T. Okada, J. Adachi, and Y. Mizoi.
Studies on the ratio between alcoholic concentrations in urine
and blood. Jpn. J. Legal Med. 27:295-306 (1973).
C.L. Winek, K.L. Murphy, and T.A. Winek. The unreliability of
using a urine ethanol concentration to predict a blood ethanol concentration. Forensic Sci. Int. 25:277-281 (1984).
A.W. Jones. Top-ten defense challenges among drinking drivers in
Sweden. Meal. Sci. Law31" 229-238 (1991).
R. Iffland. Nachtrunk und Harnprobe. Blutalkohol 36:99-105
(1999).
A.W. Jones and J. Schuberth. Computer-aided headspace gas chromatography applied to blood-alcohol analysis: importance of online process control. J. Forensic Sci. 34' 1116-1127 (1989).
M. Bland. An Introduction to Medical Statistics, 3rd ed. Oxford
University Press, Oxford, U.K., 2000.
H.E. Solberg. Establishment and use of reference values. In fietz
Textbook of Clinical Chemistry, ch. 13, 2nd ed., C.A. Burtis and
E.R. Ashwood, Eds. W.B. Saunders, Philadelphia, PA, 1994.
E.M.P.Widmark. Om alkoholens ~verg~ng i urinen saint en enkel
kliniskt anv~nbar metod f~r diagnostocering af alkoholf6rekonst i
kroppen. Uppsala L~'karef6reningensF6rhandlinagm 19:241-272
(1914).
A.W. Jones. Measuring alcohol in blood and breath for forensic
purposes--a historical review. Forensic ScL Rev. 12:151-181
(2000).
M. Ladd and R.B. Gibson. The medicolegal aspects of the blood
test to determine intoxication. The Iowa LawJ. 24:1-77 (1939).
R.L. Donigan. Chemical test case law; Legal aspects and constitutional issues involved in chemical tests to determine intoxication.
Northwestern University, Evanston, IL, 1950, pp 1-83.
W.R. Miles. The comparative concentrations of alcohol in human
blood and urine at intervals after ingestion. J. Pharmacol. Exp.
Ther. 20:265-319 (1922).
H.W. Haggard, I.A. Greenberg, R.P. Carroll, and D.P. Miller. The
use of the urine in the chemical test for intoxication. J. Am. Med.
Assoc. 115:1680-1683 (1940).
F. Lundquist. The urinary excretion of ethanol in man. Acta Pharmacol. Toxicol. 18:231-238 (1961 ).
H. Heise. Concentrations of alcohol in samples of blood and urine
taken at the same time. J. Forensic Sci. 12:454-461 (1967).
J.P.Payne, D.V. Foster, D.W. Hill, and D.G.L. Woods. Observations
on interpretation of blood alcohol levels derived from analysis of
urine. Br. Med. J. 3:819-823 (1967).
W.H.D. Morgan. Concentrations of alcohol in samples of blood and
urine taken at the same time. J. Forensic Sci. Soc. 5:15-21 (1965).
A.W. Jones. Alcohol; postmortem. In Encyclopedia of Forensic
Sciences, J.A. Siegel, P.J. Saukko, and G.C. Knupfer, Eds. Academic Press, London, U.K. 2000, pp 112-126.
P.M. Hayden, M.T. Layden, and M.D. Hickey. The stability of alcohol content in samples of blood and urine. IrishJ. Med. Sci. 146:
48-53 (1977).
W. Neuteboom and P.G.M. Zweipfenning. The stability of the alcohol concentration in urine specimens. J. Anal. Toxicol. 13:
141-143 (1989).
A.W. Jones. Lack of association between urinary creatinine and
ethanol concentrations and urine/blood ratios of ethanol in two
successive voids from drinking drivers. J. Anal. Toxicol. 22'
184-190 (1998).
P. Bendtsen and A.W. Jones. Impact of water-induced diuresis on
urine-ethanol profiles, urine-creatinine, and urine-osmolality.
J. Anal. Toxicol. 23:565-569 (1999).
A.A. Biasotti and T.E. Valentine. Blood alcohol concentration determined from urine samples as a practical equivalent or alternative to blood and breath alcohol tests. J. Forensic Sci. 30' 194-207
(1985).
Journal of Analytical Toxicology,Vol. 26, September2002
32. M. Emberton and K. Anson. Acute urinary retention in men: an age
old problem. Br. Med. J. 331]: 921-925 (1999).
33. L. Kadehjian. Urine alcohol testing; valid and reliable. Syva Monitorg: 9-12 (1991}.
34. R.H. Liu and B.A. Goldberger. Handbook of Workplace Drug
Testing, AACC Press,Washington, D.C., 1995, pp 1-390.
35. W.D. Alexander, P.D. Wills, N. Eldred, and R. Gower. Urinary
ethanol levels and diabetes. Lancet i: 789 (1981).
36. J.J.Saady,A. Poklis, and H.R Dalton. Production of urinary ethanol
after sample collection. J. Forensic Sci. 38:1467-1471 (1993).
37. RS. Lough and R. Fehn. Efficacy of 1% sodium fluoride as a preservative in urine samples containing glucose and Candida albicans.
J. Forensic Sci. 38:266-271 (1993).
38. A.W. Jones, L. Hyl~n, E Svensson, and A. Helander. Storage of
specimens at +4~ or addition of sodium fluoride (1%) prevents
formation of ethanol in urine inoculated with Candida albicans.
J. AnaL Toxicol. 23:333-336 (1999).
39. A.W. Jones, A. Eklund, and A. Helander. Misleading results of
ethanol analysis in urine specimens from rape-victims suffering
from diabetes. J. Clin. Forensic Med. 7:144-146 (2000).
Manuscript received November 26, 2001 ;
revision received March 26, 2002.
339