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PREFACEAs the title implies, the objective of this fact sheet is to provide drug court professionals with a scientifically based justification for discontinuing the interpretation of urine drug levels in an effort to define client drug use behavior. As the premise of this document is not without some controversy, clarificationof its intent seems warranted.

This fact sheet is intended for drug court practitioners who are routinely engagedin the interpretation and evaluation of urine drug testing results for the purpose ofparticipant case adjudication, particularly client sanctioning. Given that most drugcourts do not have routine access to biomedical or pharmacological expertise,this fact sheet recommends that the use of urine drug concentrations be elimi-nated from the court’s decision-making process in order to protect client rightsand ensure that evidentiary standards are maintained.

It is not the intention of this document to prohibit the interpretation of laboratorydata by qualified scientists. Nor is it the objective of this fact sheet to assert thaturine drug levels have no interpretative value. However, drug court practitionersare cautioned that the interpretation of urine drug levels is highly complex andeven under the best of circumstances provides only limited information regardinga participant’s drug use patterns. Further, such interpretations can be a matterof disagreement even between experts with the requisite knowledge and trainingto render such opinions.

It is for these stated reasons that the NDCI strongly encourages drug court pro-grams to utilize the information contained herein to evaluate their drug testingresult interpretation practices. This organization recognizes that the use of urinedrug levels to assess client behavior may be widespread and longstanding.However, because courts rarely have the necessary toxicology expertise, theroutine use of urine drug levels by court personnel in formulating drug courtdecisions is a practice that in most cases would not withstand scientific or judicial scrutiny. It is hoped that this fact sheet will serve as the foundation forthose drug court programs routinely interpreting urine drug levels to transition to a strictly qualitative (positive or negative only) result format. Drug courts arealso encouraged to seek expert toxicology advice when necessary and appropriateto assist in the interpretation of testing data associated with challenging cases.

URINE DRUG CONCENTRATIONS: THE SCIENTIFICRATIONALE FOR ELIMINATING THE USE OF DRUGTEST LEVELS IN DRUG COURT PROCEEDINGSBy Paul L. Cary, M.S.

DRUG COURTPRACTITIONERF A C T S H E E T

INTRODUCTION

While urine drug testing remains the primarystrategy for the abstinence monitoring of drug court participants, interpretation of testresults continues to be problematic for manycourts. The use of urine drug concentrations(numeric values given with positive results)for the purpose of interpretation remainswidespread. Many drug courts utilize urinarydrug levels in an attempt to quantify the druguse behavior and patterns of their client popu-lation. To make matters worse, absolute drugconcentrations are often “interpreted” with-out adjustments for differences in urine watercontent. Increases in absolute drug concentra-tions resulting from changes in urinary outputare often mistakenly interpreted as new druguse rather than carryover from previous drugexposure. Decreases in absolute drug concen-trations, which can also result from urine volume changes, can be misinterpreted asevidence of continued abstinence. Basedupon limited, anecdotal information, urinedrug levels are often arbitrarily assigned quan-titative labels such as “high” or “very high”or “almost negative” in an effort to categorizelaboratory results. Treatment providers monitorfalling urine drug concentrations in an effort to substantiate continued elimination. Manydrug courts utilize urine drug levels in aneffort to define substance abuse behavior and dispense appropriately measured justice.

At best, these interpretation practices aremisguided. At worst, the conclusions reachedregarding drug use behavior and patternsusing urine drug concentrations are just plainwrong! While well intentioned and seeminglylogical, the utilization of urine drug test levels

generally produces interpretations that areinappropriate, factually unsupportable, andwithout scientific foundation. Worst of all forthe court system, these interpretations havelittle, if any, forensic merit.

EVIDENTIARY STANDARDS

The drug court model is built upon an evidentiaryfoundation that provides maximum flexibilityto team members as they apply innovativetreatment strategies designed to succeedwhere other legal remedies have failed. Whilethis flexibility is an important managementtool, basic evidentiary standards for theadmissibility of scientific data into the pro-ceedings must be maintained. Unfortunately,as drug courts experiment with a variety oftherapeutic interventions and struggle withsanction and incentive decisions, this eviden-tiary foundation sometimes may becomecompromised. This is particularly true whenthe interpretation of drug testing results utilizes urine drug levels.

The fact that urine drug concentrations are of little interpretive value will unfortunatelycome as a surprise to too many drug courtprofessionals. The use of urine drug levels for evaluating patterns of substance abuse is commonplace and has deep roots in thecriminal justice system. Court programs havebeen adjudicating cases based on urine druglevels for years. That fact does not make thepractice any more legitimate. If the use ofurine drug levels cannot be supported scien-tifically, then the validity of decisions basedupon these levels is questionable. Accordingly,the more often a court utilizes drug testresults in a manner that is not scientificallyvalid, the farther it strays from its evidentiaryfoundation – thus undermining the forensicdefensibility of its decisions.

It has even been reported that some jurisdic-tions interpret urine drug levels that fallbelow the testing cutoff point (i.e., samplesthat have tested negative). Presumably, theevaluation of levels under the assay thresholdis an effort to uncover potential covert drug

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The fact that urine drug concentrationsare of little interpretive value will

unfortunately come as a surprise totoo many drug court professionals.

use. It is further reported that increases inthese levels (still below the testing cutoff) are used to sanction drug court clients. Notonly is the evaluation of urine drug levels in a negative sample the antithesis of the intentof drug testing, but it also violates standardsof evidence admissibility. In short, this practiceis unethical. A negative test result cannot beinterpreted in any other manner than negative.Court-affiliated attorneys, both prosecutionand defense counsel, entrusted with the pro-tection of client rights are obligated to abolishthis practice.

An unambiguous evidentiary foundation thatwill pass scientific and legal scrutiny is crucialfor the continued success of drug courts. Forthose drug courts utilizing urine drug levels to formulate court-related judgments, this factsheet is designed to provide sufficient objec-tive information to support the reevaluation of those result interpretation practices thatallow the introduction of unscientific evidenceinto the courtroom.

LABORATORY/COURT RELATIONSHIP

The controversy associated with urine drugconcentrations is complicated by the relation-ship between drug testing laboratories and thecourts. The reporting of urine drug concentra-tions as part of the drug test result receiveslittle attention within the drug testing industryitself. And if the issue does surface, the discussion often focuses on economic ratherthan scientific or ethical issues.

In performing a drug test, laboratories mustdetermine the concentration of drug in urinein order to differentiate between samples thatare reported as either positive or negative.Testing methodologies require that urine samples producing a drug concentration at or above the cutoff level of the drug test be classified as “positive” and that samplesyielding a drug concentration below the cutoff level of the test be defined as “negative”(or none detected). In other words, the solepurpose for determining a urine drug level is to allow the assignment of a qualitative

result—positive or negative. The dilemma for the laboratory is what to do with thenumeric result (drug concentration) that hasbeen generated during the testing process.

Some laboratories do not report this valueeven if requested, believing that the urinedrug concentration serves no useful purposeor could result in the misapplication of thedata. On the other hand, many drug testinglaboratories do provide the urine drug concen-trations as part of their result report. Whenasked about the practice of reporting urine drugconcentrations, most laboratories admit thatthese values are not useful for interpretationpurposes; however, numerical results continueto be reported because of customer demand.Put another way, laboratories report drug levelsbecause court professionals request thosevalues. Laboratories that report concentrationsroutinely cite customer surveys that indicatethat court programs would be dissatisfied withthe lab services if drug concentrations werenot provided (i.e., not getting their money’sworth). These surveys further suggest thatmerely reporting “positive” or “negative”results would be viewed as insufficient tomeet the court’s needs.

The vicious cycle begins. Regardless of theirnegligible merit, urine drug levels reported tothe court beg for interpretation and many courtsare all too eager to oblige. Courts becomedependent upon the drug levels provided by the laboratories for client adjudication and laboratories feel compelled to provide theconcentrations to avoid the potential adverseeconomic repercussions associated with losingbusiness due to not providing the levels. Thisresults in an apparent institutional reluctance

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An unambiguous evidentiary foundationthat will pass scientific and legalscrutiny is crucial for the continuedsuccess of drug courts.

by both the laboratory industry and the criminaljustice system to change current practices—even in the face of solid scientific evidence.Drug testing laboratories yield to the obviouseconomic forces and drug courts relying onurine drug levels for the dispensation of sanc-tions and rewards are not inclined to changeor find the practice difficult to eliminate.

DRUG TEST MANUFACTURERS’RECOMMENDATIONS

By way of review, the drug tests used bydrug courts are qualitative. That means thatthe purpose of the test is to determine thepresence or the absence of a drug in a urinesample being tested – period. Either a drugtest is positive (drug presence at or above the cutoff concentration) or negative (nonedetected; drug level below the cutoff concen-tration). These tests were not designed ormarketed to produce quantitative results –how much drug is present in the sample.

The product information materials for themost popular laboratory-based drug testmethod in use in the U.S. (available since1974) states the following:

• “A positive result from the assay indicates the presence of drug but does not indicate or measure intoxication.”

• “Interpretation of results must take intoaccount that urine concentrations can vary extensively with fluid intake and other biological variables.”

• “Immunoassays that produce a single resultin the presence of a drug and its metabolitescannot fully quantitate the concentration ofindividual components.”

• “When the test is used as a qualitative assay, the amount of drugs and metabolitesdetected by the assay in any given specimencannot be estimated. The assay results distinguish between positive and negativespecimens only (Dade Behring, SYVA®, 2003).”

This product information unequivocally estab-lished the qualitative nature of urine drug testing. Similar directives may be found in the product literature of essentially all drugtesting products. The basis for this product

guidance is both technical (issues associatedwith the testing methodologies) and physio-logical (how the human body processes drugs).

TECHNICAL ISSUES AFFECTINGINTERPRETATION OF DRUG LEVELS

First, qualitative drug tests are generally notlinear. That means that the urine drug concen-tration being reported may not be precisebecause the testing instrument’s response tovarying drug concentrations is not a straightline. At high drug concentrations or low drugconcentrations the values produced may notaccurately reflect the actual concentration ofdrug in urine. Qualitative tests are not designedto accurately quantitate drug concentrations;the purpose of these tests is to determinewhether the drug level in urine is greater thanor less than the cutoff – positive or negative.Therefore, at the high concentrations (wellabove the cutoff) or at the low concentrations(significantly below the cutoff) the drug levelsdetermined by the test may be skewed simplydue to the concentration of the drug itself and the inability of the test to measure thatconcentration accurately.

Second, many initial screening tests detectboth the presence of parent drug(s) and theirmetabolites (chemical breakdown products)simultaneously. That means that the numericresult reported represents a total concentrationof the mixture of similar drug components(i.e., total amount of vegetables in a soup).These drug and drug metabolites are detectedby the tests differentially. In other words,each individual component produces a distinctand dissimilar reaction (i.e., the peas in the soupproduce a greater response when countedthan the same number of carrots). With aqualitative test it is impossible to determinewhat portion of the total drug concentrationbeing measured is associated with the primarydrug and what portion is associated with themetabolites (i.e., what portion of the totalmeasured vegetables in the soup is peas andwhat portion is carrots). Therefore, attemptingto evaluate a urine drug level based upon a

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result that measures total drug concentration(of continually changing concentrations of drugand drug metabolites levels) is not possible.

PHYSIOLOGICAL ISSUES AFFECTINGINTERPRETATION OF DRUG LEVELS

Drug concentrations in the urine are presentin proportion to the total amount of liquid. Ifthe urine is diluted, the concentration of thedrug is reduced and when the urine is moreconcentrated the drug concentration isincreased. Urine volume or output is highlyvariable (both from person to person andwithin the same person at different times during the day) and is influenced by a varietyof factors, including: liquid, salt and proteinintake, exercise, and age. The variability ofdrug concentrations due to changes in urinevolume is significant. Drug levels may varywidely within a day or between days evenwith no additional drug exposure as a resultof fluid intake alone. Without some form ofnormalization technique (some drug courtsuse creatinine concentrations to correct forthe variations that occur in urine volume) theinterpretation of urine drug levels is fraughtwith inaccuracy.1

As mentioned in the previous section, initialscreening tests for drugs detect both thepresence of parent drug(s) and their metabo-lites (chemical breakdown products) simulta-neously. As drugs and their breakdown prod-ucts are eliminated from the body they areexcreted at differing rates – those that areless water-soluble are often eliminated moreslowly than those that are more water-soluble.This results in a continually changing ratio ofcompounds that are reacting to the test (i.e.,peas are eliminated more quickly than carrots;subsequent tests measure greater amountsof carrots). Due to the fact that these compo-nents are eliminated from the body at differentrates, thus varying the overall test response,

any attempt to evaluate changing urine druglevels that are based upon a result that meas-ures total drug concentration (drug and drugmetabolites) becomes extremely problematic.

THE BLOOD ALCOHOL MODEL

Judges and courts have relied on quantitative(numeric) testing data for decades in makingsentencing decisions; most notably, the interpretation of blood alcohol levels for thepurposes of establishing intoxication andimpairment. Unfortunately, the interpretationof blood alcohol concentrations cannot serveas a model for evaluating urine drug levels. In fact, the ease with which society legislatesand litigates around BAC’s has likely exacer-bated the problem associated with under-standing the limitations of urine drug levels.The blood alcohol model may have inadvertentlyled to the fallacy that drug levels in any bio-logical fluid can and should be interpreted.

When it comes to the testing of urine, it mayseem logical to make the assumption that drugconcentrations are related to either a specificphysiological response or that urine drug levelscorrelate with drug usage patterns. But thecorrelation between blood (as a specimen)and alcohol (as a drug) from an interpretationperspective could not be more different fromthe interpretation of urine drug testing results.The interpretation of blood alcohol concentra-tions is relatively straightforward because: (1) alcohol is a simple molecule, (2) blood is thebiological specimen most closely associatedwith the site of drug action (receptor), and (3) the study of alcohol levels and their effectson humans spans nearly 100 years. By contrast:(1) abused drugs have very complex chemicalstructures, (2) urine is a waste specimen notassociated with the pharmacological activityof the drug, and (3) research associated withabused drug concentrations and physiologicalresponse is in its infancy (compared to alco-

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1. For additional information on the use of creatinine to normalize results, see also: “The Use Creatinine-Normalized Cannabinoid Resultsto Determine Continued Abstinence or to Differentiate Between New Marijuana Use and Continuing Drug Excretion From PreviousExposure”, Drug Court Review, Volume IV, Issue 1, Summer 2002, pages 83-103.

hol). It is for these reasons that eleven notedtoxicologists, in a consensus report regardingthe interpretation of urine drug testing resultsin a forensic context, wrote:“Testing of drugs or drug metabolites in urine isonly of qualitative value in indicating some priorexposure to specific drugs. Inferences regardingthe presence or systemic concentration of thedrug at the time of driving or impairment fromdrug use are generally unwarranted (ConsensusDevelopment Panel, 1985).”

Few outside the scientific community realizethat even when measuring drugs in blood (asopposed to urine), that many of the abuseddrug levels commonly quantitated areextremely difficult to interpret or even to cor-relate with specific physiological responses.Not surprisingly, scientists generally agree thatthere is no correlation between urine drug levels and pharmacological action. Since thereis no recognized correlation between urinedrug levels and drug action, it is not difficultto understand why attempting to interpreturine drug levels is not scientifically valid.

A urine drug level does not indicate whetherthe drug has been used frequently or only asingle time. Levels do not indicate the strengthof the drug being used or when the drug waslast used. Urine drug levels do not indicatewhether a person was under the influence or intoxicated by the drug at the time of thesample collection. Urine drug concentrationscannot tell the drug court whether new druguse has occurred or the value is associatedwith continued elimination from a previousexposure. Numeric results do not accuratelydiscriminate between whether a participant’soverall drug level is increasing or decreasing –

even if compared to previous urine drug concentrations from the same client, for thesame drug. (This excludes those courts thathave adjusted drug levels based upon urinecreatinine concentrations.) Without extensivestudy under controlled conditions, no singleurine drug test can reliably answer any ofthese questions.

WHAT INFORMATION CAN BE OBTAINEDFROM A URINE DRUG TEST? A positive drug test indicates prior exposureto the drug detected. A negative drug testindicates either the specimen does not containthe drug or the drug is present in concentrationsbelow the cutoff level of the assay. Repeattesting of clients at regular intervals canimprove the interpretation of positive results.Multiple positives over a period of time rein-force that an individual may be regularly usingthe drug(s) being detected. For individualsknown to have chronically used drugs prior to the start of urine drug testing, collection ofmultiple urine samples over a period of timerequires special attention. While continueddrug excretion from previous exposure is afactor in multiple positive tests, this explanationis only valid until such time as the drug beingdetected should have been eliminated fromthe body. Accordingly, continuing positivedrug test results cannot be related to drugexcretion from previous exposure indefinitely.Multiple negative or “none detected” resultsprovide evidence that an individual is main-taining abstinence and not using drugs on aregular basis. As mentioned earlier, the use of creatinine-normalized urine results mayenhance interpretation. For cannabinoids, thisapproach allows the differentiation betweennew marijuana use and positive test resultsassociated with continued drug excretionfrom previous marijuana exposure.

ELIMINATING DRUG LEVELS

Has the urine drug level increased or decreasedsince the last test? How positive is he/she?Does this level indicate relapse? The level

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The blood alcohol model may haveinadvertently led to the fallacy that

drug levels in any biological fluid can and should be interpreted.

continues dropping so that indicates continuedelimination, correct? If any of these questionsare being asked within the drug court setting,it is almost certain that urine drug levels arebeing used inappropriately in the court’s deci-sion-making processes. For those court pro-grams that use urine drug concentrations tomake sentencing decisions, the transition to anon-numerical drug report format (i.e., resultssimply reported as positive or negative) maybe difficult. However, there are benefits. Firstand foremost, the court moves forwardsecure in the knowledge that its rulings havea strong scientific basis and are forensicallysound. Second, the court no longer has toattempt to interpret data that is not inter-pretable. Third, courts that have eliminatedthe use of urine drug concentrations havereported greater confidence in their decision-making process. Making decisions basedentirely on either positive or negative reportsremoves the judicial ambiguity associated withmanipulating numbers that few individuals, ifany, in the court environment are trained tounderstand. Lastly, the use of urine drug testresults that do not rely on concentrations addsadditional fairness and equity to the rewardsand sanctions process of the drug court. Byremoving the unpredictable urine drug levelsfrom the decision-making equation, courtseliminate the unsupportable foundation onwhich these interpretations are based.

It is noteworthy that in the federal workplacedrug testing programs (DOT, DOE, DOD, etc.),the routine reporting of urine drug levels isnever permitted. Federally certified laborato-ries are never allowed to report the numericalvalues generated from initial screening proce-dures. These protections that are provided tofederally regulated employees should serve to further illustrate the validity concerns asso-ciated with using urine drug concentrations in the drug court environment.

FINAL THOUGHTS

Mark Stevens and James Addison may havesaid it best. In an article entitled, “Interface ofScience and Law in Drug Testing” they wrote:

“In short, there is a substantial gap between the questions that the legal community wouldlike to have answered by drug testing and theanswers that the scientific community is ableto provide. The real danger lies in the legalcommunity’s failure to “mind the gap” bydrawing unwarranted inferences from drugtesting results (1999).”

When a drug court uses urine drug concentra-tions as the evidentiary basis in support of aruling (a practice that likely would not with-stand a serious legal or scientific challenge),the interpretation is performed by court pro-fessionals who generally lack background ortraining in pharmacology, toxicology, or fieldsrelated to drug testing. Accordingly, the courtcannot be expected to fully comprehend andapply the many physiological variables associ-ated with the pharmacology of abused drugsin the human body or the scientific and tech-nical issues of detecting those drugs in bio-logical fluids. However, by using urine drugconcentrations in a forensic context, the drugcourt assumes and accepts the responsibili-ties (and liabilities) associated with that scien-tific knowledge – its use and misuse. Therefore,it is incumbent upon each court to determinethe appropriateness of its use of drug testsresults in the dispensing of justice. Drug courtshave been portrayed as models of effectiveand appropriate jurisprudence. However, the continued use of urine drug levels in thedetermination of sentencing decisions repre-sents a practice that is ultimately detrimentalto the process of justice.

Urine drug testing is qualitative – the purposeof a drug test is to determine the presence orabsence of a drug in a urine sample – nothingmore! Eliminating drug levels will not make

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Making decisions based entirely oneither positive or negative reportsremoves the judicial ambiguity associated with manipulating numbers

urine drug testing results any less reliable oruseful. However, the continued use of urinedrug levels by drug courts in an attempt tointerpret drug test results will likely result inboth inappropriate and unfair rewards andsanctions for participants. Attempting toextract information from a drug test result in order to develop conclusions about urinedrug concentrations, however well-intentioned,cannot be supported by the science and represents an adjudication practice that issimply not forensically defensible.

Paul L. Cary, M.S. is the Director of the Toxicology & Drug Monitoring laboratory, University of MissouriHospital and Health Care System, Columbia, Missouri;and NDCI Faculty Resident Expert on drug testing issues.Mr. Cary can be reached at carypl@health.missouri.edu.

This document was published with support from theOffice of National Drug Control Policy, Executive Office of the President and the Bureau of Justice Assistance,U.S. Department of Justice.

References

Cary, P.L. (2002). The use of creatinine-normalized cannabinoid results to determine continuedabstinence or to differentiate between newmarijuana use and continuing drug excretionfrom previous exposure. Drug court review,4(1), 83-103.

Consensus Development Panel. (1985, November 8).Consensus report: Drug concentrations anddriving impairment. Journal of the Americanmedical association, 254(18).

Dade Behring, SYVA®. (2003, July, Revised). Emit® II Plus Enzyme Immunoassay product informationsheet. Cupertino, CA: SYVA Company.

Stevens, M.P., & Addison, J.R. (1999, December). Interface of science and law in drug testing. The Champion, 23(10), 18-24.

Publisher

C. West Huddleston, III

Director, National Drug Court Institute

National Drug Court Institute

4900 Seminary Road, Suite 320Alexandria, VA 22311703.575.9400 ext. 13703.575.9402 faxwhuddleston@ndci.org

Test your new knowledge. Answerthese true and false questions basedon the Fact Sheet text.

1. Urine drug levels are similar to blood alcohol concentrationsin that they may be used todetermine the impairment or intoxication status of the individual being tested.

2. In addressing the complexitiesassociated with various sanctionand incentive options, cocaineurine levels may be utilized inthe decision making process.

3. Any fluid intake changes an individual’s urine drug level.

4. Laboratories will not reportdrug testing results without a numerical value becausetesting manufacturers haveindicated in their product literature that such measure-ments are important to resultinterpretation.

5. Certified laboratories are neverallowed to report the numericalvalues produced by screeningprocedures for drug tests per-formed on federally regulatedemployees.

6. Evidence admissibility standardsfor drug courts are less restric-tive because in many courtsthe participants have alreadypleaded guilty.

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FACT SHEET QUIZ: WHAT DID YOU LEARN?

Answers:1. False; 2. False; 3. True; 4. False; 5. True; 6. False