Comparison of urine to sweat patch test results in court

Comparison of urine to sweat patch test results in court ordered testing 10.1016/803 79-07... Page 1 of 4
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Forensic Science International
Abstract
Keywords
1. Introduction
2. Case sludy
Comparison of urine to sweat patch test results in court ordered testing
--
L-X:
Joseph A. Levisk)i' ' .., . 0 . David L Bowennan'', Werner W. Jenkins', Deborah G. Johnson' .
JohnS. Levisky', Sleven B. Karch•
, El P~.so County Cofor.cJf'.s OffiCe. COIOfoa® Spnc~, CO 8090G, USA
3. O.seussion
3. 1. Sensitivicy
3.2. Specifici ty
3.3. Efficlency
11
B<e:hnvioral Scl..,nc:, Department. Yo1-k Collooe of PP.Ot'I$Yivnn.a, Yot1t. PA. l 740S, USA
'Cdy a11d County of SM Fra~. tiall of Jus.tioa_. 850 Btylrtl Street, San Fmncl<&co, CA 9.i tG3, USA
Aeknowledgemenls
http·!.'d.-. dci,otg!1 0. 101GIS0-319-073e(01)004<4~ I. MowN C.&iJ OJ Ur~ Usin; 001
P et~kln., & Rtprint&
References
Q Publishing
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Abstract
A fonner cocaine and methamphetamine abuser was continuously monilored with both sweal patch and
urine testing for approximately
6 months.
Thirteen sweat patches were applied and collected, five were
positive for cocaine and/or methamphetamine. but all the urine specimens coltocled were negalive at the
Author
analytical cut-off levels. The high incidence of falsG positive sweat pat.ch tests in relation to the sensitivity,
specifiCity, and efficiency of the sweat patch assay is discussed. Possible mechanisms, which can lead to
Training
false positive results, are presented. The results of our study raise further questions about the preferential
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use of the sweal patch in detecting new episodes of drug use in formerly chronic drug users.
T•ps on how to
Keywords
get published
Sweet patch; Cocaine; Methamphetamine; Sensitivijy; Spedflcity: Efficiency; False positive
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1. Introduction
Two recent sludies from the Addiction Research Center assessed the sensitivi1y, specifiCity. and efficiency
of sweat patch versus urine testing In a group of 44 methadone maintenance patients. For the sw eat patch
deteclion of concurrent cocaine use. the sensitlvily was 97.6 %, specificity 60.5%, and efficiency
n .7%;
and, for opiale use, the corresponding values were 68.6. 86. 1, and 78.6% (1} and (2}. The relatively k1.v
values for specificity and effiCiency raise eoncems about whether sweat patch testing is the appropriate
methodology to be used when false positives can lead to serious or adverse action against the tesc subject.
We r ecenUy had the opportunity lo compare test results of
o sequential series o f urine specimens and
sweat patches of a probationer, whicl1 were collected continuously over a 6 monlh period. Our fondings
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Pc.utt"'Cf1119 wnh tht~ Glob.;\l
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confinn the low specificity and etroclency values repol1ed in the earlier studies.
2. Case study
A 35-year-old woman with a history of chronic methamphelamlne and cocaine abuse was ordored by lhe
courts fo undergo drug monitoring. She reported uslng bolh drugs interchangeably. When abusing
m ethamplletamfne, she consumed, on average, a gram a day. When abusing cocaine. she consumed 2-
4 g per day. Her period o f heaviest drug use occurred d.-ing the 3 months just pnor to the commencement
of drug monitoring. The court ordered that she submit to sweat patch monlloring. However, she also
eloc!ed to have observed urine specimens colloc!ed and anatyzed for companson. Fig. 1 displays the
Inclusive dates the sweat palch was worn with test results along with the dates and resuns of the urine
conactions.
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Comparison of urine to sweat patch test results in court ordered testing 10.1016/S0379-07 ... Page 3 of 4
more likely it is lhat drug use will be detected. By definition. a False Positivo Test result does not altor lhe
sensitivity value of a tesl. That means lhen. that a tost with a very high degree of sensitivity is not always
desirable. ospeciaRy when a falsa positive may result in incarceration Of loss of child custody for the person
being tested.
3.2. Specificity
Tho specificity of a lest charnctorites the irn:idence of true negative results when a test is applied to
subjects known to be free of disease, or
Specificity=
(~)
TN + FP
X
100
where TN is true negative and FP is false positive.
Unlike sensitivity, specifocity is greatly influenced by the number of false positives. A positive sweat patch
test In relation to all negative urine tests while the patch is being wom is defined as a false positive
[t] and [2). A specifiCity oft 00% means that if drugs are not used while lhe sweat patch is being worn. both
lhe sweat patch test and the urine tesls wiU always be negative. As the numberoffalse positives inereasos,
the specificity of the test decreases. Compared to urine testing, the specificity of sweat patch tests fOf
cocaine detection is reported to be between 60.5 and 62.9% (11. A test with the highest specificity is desired
when the occurrence ol a single False Positive lest can lead to serious and adverse action against the test
subject. By this definition, all the positive sweat patches reported for lhis subject were not true positives.
bulln fact were false posiUves.
3.3. Efficiency
The efficierocy of a test is defined as the percent of all resuhs lha1 are true results, whether positive Of
negative. or
Efficiency=
(TP~l'N)
x
tOO
wh&re Nis lhe total number of tests.
If a test is 100% efficient. the test represents lhe true condition all lhe time. An efficiency of <80%. as was
the case in lhe clinical stud1es for cocaine and opiate detection [1] and [21. suggests the assay represents
true results <80% of lhe time. A lest wilh the highest effici&rocy is desired when both false positive and false
negative results are equally serious and damaging. False positives and false negatives present something
of a conundrum. False Positive tests damage the probationer. while False Negative tests can be said to
damage lhe justice system by allowing drug users to go free. in spite oflhe court.s orders.
SWeat patch proponents argue that, in lhe case of cocaine abuse, !he lest has a 97.6% sensitivity. which
means lhat the test can be reNed upon to detect drug use when drug use occurs. However. should a test for
cocaine detection with a specificity of 60.5% and a 21 .1% false positive rate (1] be acceptable? In
monitoring opiate use, Huestis el al. [2] reported a false positive rate of as high as 7.9%. Of 44 monitored
subjects. 15 subjects had positive sweat patches during weeks when all corresponding urine tests were
negative. During lhe course of the study. one of the test subjects had six positive sweat patches associated
wilh aU negative urine tests. and >30% of the participants had at least. one false positive sweat patch at
some times during the study.
There are several possible mechanisms that might explain the high incidence of false positive sweat patch
tests. Licit and illicit drugs are readily identified in skin and adipose tissues of cod avers, and their presence
is a luncUon of antemortem deposition, not postmortem redistribution 141 and [5). Juler et al. [6] reponed
that chronic cocaine users exhibit prolonged terminal urine hall· lives lor cocaino and metabolites and
suggested that cocaine might accumulate in the fatty liuues of the body. Slow release from lhese tissues
might accoontlor the prolonged elimination. Subjects who undergo court ordered drug testing undergo
testing for a reason. and lhe reason is usually lhat they aro chronic drug users. The time it takes to clear all
resio:klal drug from their bodies has never been studied and is not known.
There Is also evidence to suggest that drugs can migrate from adipose tissues to the skin surface via extra·
circulatory routes [4] and (7]. Others have suggested lhal skin·tcrskin contact is another possible
mechanism of drug deposition on the sweat patch. Kidweii[SI demonstrated thai drugs applied to the skin
surface remain on lhe skin surface lor days and that simple cleansing does not remove aU lhe drug. Joseph
et at [91 Showed thai cocaine per$lsts for several weeks In the stratum cometKn (the outer layer of the skin)
in chronic drug users. Individuals who must wear sweat patches have husbands. live.in lovers, and friends
who may continue to use drugs. It is not surprising lhat the sweat patch wearer may unknowingly be
exposed to these drug sources.
Whether one Of all of these mechanisms contribute to the problem is not known, and will never be known
until the appropriate studios are undertaken. Untd such studies are undenaken lhe appropriateness of lhe
sweat patch methodology. at least for use by lhe cour1S, remains in doubt.
Acknowledgements
The aulhOfS gratefully acknowledge lhe expert technical assistance of Mrs. Sandy Way. Ms. Cynthia
Vislocky and Mrs. Jeanine Jenkins In lhe research and preparation of this manuscripl
References
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K L. Preston, M.A. Huestis, C.J. Wong. A. Umbricht. B.A. Goldberger. E.J. Cone
Monitoring cocaine use In substance-abuse-treatment patients by sweat and urine testing
J.Anal. Toxiool., 23 (1999). pp. 31~32 1
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3/17/2012
Comparison of urine to sweat patch test results in court ordered testing 10.10 16/S03 79-07 ... Page 4 of 4
(
(2)
M.A. Huestis. E.J. Cone. C.J. Wong. A. Umbricht, K.l. Preston
Monitoling opiate use In substance abuse Ilea!mont patients with sweat and urine drug testing
J. Anal. T<»rico!.• 24 (2000). PJl. 50S-52 I
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R.S. Galan. S.R. Gamblnu. Beyond Norm.-1fity. Tt1o Pr&dlctlva Vaiue and f flicltWlCy of M&dicai Diagnosol\,
Wiloy, Now Yo11<. 1975.
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J.A Levisky, D.l. Bowerman, W.W. Jenkins. S.B. Karch
Drugs depos~ion in adipose tissue and skin: evidence for an aHemalive soon::e of positive swea1
palchtesls
For.Sci.lnl., 1 11 (2000). Jlll, 35-·46
(
(5)
JA Lemky. C.l. Bowerman, W.W. Jenl<ios. O.G. JOhnson, S.B. Karcll. Drugs lfl poslrnOriem adipose Wsue11:
evidence Q! antemottetn dopo$11100, F<><. Se>encolnt. in press.
t
[G)
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Elimination of cocaine and metabolnes in plasma, saliva, and uriM following repealed oral
adminislmllon to human volunteers
J. AM!. Toldcol., 2-1 (7) (2000). pp. •67-477
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M. Bums, R.C. Basel!
Monitoring drug u.se with a sweat patch: and experiment with cocaine
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(
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•-t (WbiiShed el1'0tum
appears in J. Chtomatog. B. e.orno<l. SCL Appl. 721 (2) ( 1999) 333). J. Chromatog. B. eootl'ed. Sci. Appl. 713
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[9)
R.E. Joseph Jr.. J.M. Oyler, AT. Wstadillc. C . Ohuoha, E.J. Cooe
Drug ti!SOOg wilh alternative matrices 1. Phannacological effect and disposilion of cocaine and
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(
ol.
Corresponding author.
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