Drug screening in urine--common pitfalls in measurement and interpretation

Nowadays immunoassays are used for the rapid screening of drugs world-wide. Despite the fact that they are a highly valuable tool for the test of legal and illicit drugs, there is a non-negligible risk of false positive and false negative findings, and many pitfalls must be taken into account when using these tests in an uncritical manner and without valid confirmation procedures. In accordance with the committee for "problems of threshold values for medical and addictive drugs" set up by German scientific societies (in particular GTFCh, DGRM and DGVM), immunoassays are recommended as a useful tool for screening. But confirmation analysis with conclusive methods (GC/MS or LC/MS) is indispensable for valid substance identification, discrimination between active and inactive metabolites, detection of escort substances and accurate determination of concentrations in body fluids.     

Correlation of the incidence of cocaine and cocaethylene in hair and postmortem biologic samples

Hair samples are useful as a matrix for drug testing because drugs can be detected in hair for longer periods than in blood or urine. The authors report a prospective comparison of the detection of cocaine and cocaethylene in routine postmortem biologic specimens to the detection of cocaine and cocaethylene in hair. The authors collected hair samples from various areas of the head in 53 autopsy cases, prepared them, and analyzed them by gas chromatography/mass spectrometry (GC/MS) for cocaine and cocaethylene. The authors compared the results of hair analysis with the results of toxicologic analysis performed on routine postmortem samples by enzyme multiplied immunoassay technique and GC/MS. Cocaine was found in either biologic fluids or in hair in 16 of 53 samples tested. Nine samples were positive for cocaine in both biologic fluids and hair. Five samples contained cocaine only in biologic fluids, and two contained cocaine only in hair. Cocaethylene was present in two cases. Drug screening of hair provides additional information in some autopsy cases, but the authors have not made hair analysis a routine practice. It may prove useful to save hair samples in all cases for later analysis if warranted by additional history or autopsy findings.     

Value of hair analysis in postmortem toxicology

It is generally accepted that chemical testing of biological fluids is the most objective means of diagnosis of drug use. The presence of a drug analyte in a biological specimen can be used to document exposure. The standard in postmortem drug testing is a general unknown screening, followed by the gas chromatographic/mass spectrometric confirmation conducted on a whole blood sample. In recent years, remarkable advances in sensitive analytical techniques have enabled the analysis of drugs in unconventional biological specimens such as hair. The advantages of this sample over traditional media, like urine and blood, are obvious: collection is almost non-invasive, relatively easy to perform, and in forensic situations it may be achieved under close supervision of law enforcement officers to prevent adulteration or substitution. Moreover, the window of drug detection is dramatically extended to weeks, months or even years. The aim of this review is to document the current status of hair analysis in postmortem toxicology.     

Determination of opiates and cocaine in hair using automated enzyme immunoassay screening methodologies followed by gas chromatographic-mass spectrometric (GC-MS) confirmation

The objective of this study was to develop a two-step strategy for analysis of opiates and cocaine in hair samples involving an immunological screening procedure followed by confirmation of results using gas chromatography-mass spectrometry (GC-MS). A semi-quantitative automated competitive enzyme-linked immunosorbent assay (ELISA) methodology using Oral Fluid Micro-Plate Enzyme Immunoassays (Orasure Technologies, Inc.) was developed and validated. Applicability was proven by analysis of authentic head hair samples from drug users (n=103) and from opiate associated fatalities (n=21). The optimum cutoff values for the ELISA tests were 0.1 ng cocaine-equivalents/mg hair and 0.05 ng morphine-equivalents/mg hair using a 50 mg hair sample. Both ELISA tests had a sensitivity of 100%, the specificity was 66% for cocaine-equivalents and 42% for morphine-equivalents. The intraassay precision was 11% for the cocaine and 3% for the opiates ELISA, while interassay precision was 12% for the cocaine and 4% for the opiates ELISA test. The actual analyte concentrations in the hair samples were determined using GC-MS and were between 0.04 and 5.20 ng/mg for heroin (HER), between 0.04 and 30.01 ng/mg for 6-monoacetylmorphine (MAM), between 0.03 and 11.87 ng/mg for morphine (MOR), between 0.02 and 1.84 ng/mg for codeine (COD), between 0.02 and 2.48 ng/mg for acetylcodeine (AC), between 0.01 and 21.37 ng/mg for cocaine (COC), between 0.03 and 10.51 ng/mg for benzoylecgonine (BE) and between 0.05 and 1.26 ng/mg for cocaethylene (CE). The automated ELISA tests were proven to be valid screening procedures for the detection of cocaine and opiates in hair as confirmed by GC-MS. Screening methods provide rapid and inexpensive automated pre-test procedures to detect drugs in hair or other matrices. For forensic purposes screening therefore represents an ideal complement to routinely applied GC-MS procedures.     

Segmental Hair Analysis—Interpretation of the Time of Drug Intake in Two Patients Undergoing Drug Treatment

The present study involved segmental testing of hair in two clinical cases with known dosage histories. Hair analysis confirmed the first patient's exposure to the prescribed sertraline and citalopram for several months. Citalopram was generally distributed along the hair shaft in accordance with the drug ingestion period. By contrast, “false” positive results were observed for sertraline in distal hair segments, corresponding to a period of no sertraline exposure, which may indicate incorporation from sweat or sebum, which transport the drugs along the hair surface. The second patient received various drugs during her treatment for brain cancer. Metoclopramide, morphine, oxazepam, paracetamol, sumatriptan, tramadol, and zopiclone, which had been part of the therapy, were all detected in the proximal hair segment. The results of these two cases indicated that results—especially concerning the time of drug intake—must be interpreted with caution and allow for the possibility of incorporation from sweat or sebum.     

Detection of drugs in human hair using Abbott ADx, with confirmation by gas chromatography/mass spectrometry (GC/MS).

The authors suggest use of the fluorescence polarization immunoassay (FPIA) technique in evaluation of chronic drug abuse using human hair. Hair was decontaminated in 5 mL of ethanol for 15 min at 37 degrees C and then incubated in 3 mL of 1M sodium hydroxide (NaOH) for 1 h at 100 degrees C. Afterwards, the aliquots were neutralized and analyzed using Abbott ADx for a negative or positive response for the following drugs: benzodiazepines, barbiturates, antidepressants, opiates, cocaine, amphetamine, and cannabis. All the positive samples were confirmed by gas chromatography/mass spectrometry (GC/MS). Only one false positive was detected (caused by interference of a phenothiazine with the antidepressants kit), clearly demonstrating the capability of ADx for toxicological screening of human hair.     

Drug testing by urine and hair analysis: complementary features and scientific issues

Hair analysis and urinalysis are complementary tests for establishing drug use. Hair analysis provides long-term information, from months to years, concerning both the severity and pattern of drug use. In contrast to this, urinalysis can indicate only drug use, and then generally only that which has occurred within the last 2–3 days. Field studies have demonstrated that hair analysis is considerably more effective than urinalysis at identifying drug users. This difference is due to the wider surveillance window of hair analysis and to the susceptibility of urinalysis to evasive maneuvers. The main concerns with urinalysis are endogenous evidentiary false positives caused by passive drug exposure, e.g., ingestion of poppy seed. This problem arises from the hypersensitivity of the urine test, i.e. the need to use low cut-off levels in order to compensate for the temporary recording of drug use. This problem does not occur with hair analysis since its wide window of detection and permanent record of drug use ensure that the detection efficiency of the test is not compromised by the use of more effective cut-off levels guarding against passive endogenous drug exposure. On the other hand, exogenous evidentiary false positives due to external contamination of hair by drugs present in the environment (e.g., smoke) are the main concern of hair analysis. This problem, however, can be effectively avoided by washing the hair specimen, by kinetic analyses of the wash data, and by measurement of metabolites. The possibility of bias due to race and/or hair color is avoided by the exclusion of melanin from the analysis of hair. The safety and effectiveness of hair testing has been established by extensive field studies with over 400 000 specimens.     

Evidence for bias in hair testing and procedures to correct bias

A number of in vitro experiments show that different hair samples incorporate differing amounts of drugs under identical conditions. Incorporation of cocaine and morphine tends to be correlated with race, in that the hair of African American females incorporates higher concentrations of cocaine than does the hair of Caucasian males or females. Extrapolation of these data into populations has been fraught with difficulties because the dosages of drugs and their use patterns are unknown. Cosmetic treatments and hygiene alter drug binding, which must be considered in comparing populations because cosmetic treatments are often group dependent. Four reasons are proposed that account for the uptake and retention of drugs by hair and that may differ among groups: (1) permeability and other characteristics of the hair due to genetic influences, (2) cosmetic hair treatments and hair care habits (which may be culturally influenced), (3) drug removal during personal hygiene, and (4) manner and route of drug administration which can affect passive exposure to residual drugs in the environment. The data supporting bias in hair testing are reviewed and methods are proposed that use either the uptake of dyes or the incorporation of drug homologs to reduce bias.     

Evaluation of the IDS One-Step ELISA kits for the detection of illicit drugs in hair

This work presents the validation of a new immunological assay, the One-Step enzyme-linked immunosorbent assay (ELISA) tests from International Diagnostic Systems Corp. for the screening of drugs of abuse (cannabis, amphetamines, opiates, and cocaine) in human hair, with subsequent GC-MS confirmation. After decontamination and segmentation into small pieces, 50 mg of hair sample were incubated in 1 ml of methanol during 16 h at 40 degrees C. A 100 microL aliquot was collected and evaporated to dryness in presence of 100 microL of methanol/hydrochloric acid (99:1, v/v) to avoid amphetamines loss. The dried extract was dissolved in 100 microL of the "sample and standard diluent" solution included in the kit. This solution was submitted to analysis according to the recommended instructions of the manufacturer. During the validation phase, GC-MS confirmations were conducted according to our fully validated and published methods for opiates, cocaine, cannabis, and amphetamines determinations in hair. In a last development step, these procedures were slightly modified to directly confirm ELISA results by GC-MS using the methanolic extract. Ninety-three specimens were simultaneously screened by the ELISA tests (103 for tetrahydrocannabinol (THC)) and confirmed by GC-MS. Twenty were found positive for cannabis (THC: 0.10-6.50 ng/mg), 21 for cocaine (0.50-55.20 ng/mg), 24 for opiates (6-acetylmorphine (6-AM): 0.20-11.60 ng/mg, MOR: 0.20-8.90 ng/mg, codeine (COD): 0.20-5.90 ng/mg), and 13 for amphetamines (AP: 0.20 and 0.27 ng/mg, methamphetamine (MAP): 0.30 and 1.10 ng/mg, methylenedioxymethamphetamine (MDMA): 0.22-17.80 ng/mg). No false negative results were observed according to the Society of Hair Testing's (SoHT) cutoffs (0.5 ng/mg for cocaine, 0.2 ng/mg for opiates and amphetamines, and 0.1 ng/mg for THC). The One-Step ELISA kits appear suitable due to their sensitivity and specificity for drug of abuse screening in hair. This technology should find interest in workplace drug testing or driving license regranting, especially when many samples have to be tested with a high rate of negative samples, as ELISA is an easy and high-throughput method.     

The recovery of illicit drugs from oral fluid sampling devices

Testing for drugs in oral fluid is a convenient procedure for determining recent drug use. A number of issues are still to be resolved and this paper investigates the effects of storage systems on drug stability and recovery using three different collection devices supplied by Cozart, Immunalysis and Microgenics (third party). Drugs were analysed using a range of immunoassay systems followed by MS confirmation and quantitation. The reproducibility of the weight of specimen collected was excellent (CV<10%) for the three collection devices tested. Of the three systems studied, only the Cozart product gave acceptable recovery of THC from drug-spiked oral fluid. A combination of Cozart, Immunalysis and Diagnostix immunoassays with the Cozart collection system gave the most sensitive and discriminating screening assays for the drugs studied, namely THC, benzodiazepines, methamphetamine and morphine. Storage at either 5 degrees C or room temperature had no significant effect on drug recoveries.     

Drugs in prehistory: chemical analysis of ancient human hair

Concern about drug abuse in modern populations has led to the development of specific methods for identification of cocaine, opiates and cannabis in human hair. Drug use in prehistory can provide indirect evidence of interpopulational contact and social stratification. This paper reports drug evaluation in nineteen ancient hair samples from archaeological sites in northern Chile. Each sample was tested for the presence of traces of cocaine, opiates and cannabis, in order to establish a standard methodology for studies of drug use among prehistoric groups. Although results are negative, this absence of evidence could be due to two main causes: (1) the individuals evaluated did not use any drugs, which does not mean that other members of their cultural group did, or (2) the wide range of known drugs studied did not consider some group specific drugs, derived from local or imported plants, thus meaning that a greater drug range must be tested. In any case, our study confirms that drug testing in prehistoric samples is viable. However, in order to determine what kind of substances were used in prehistoric times new patterns that incorporate all drugs which are not part of the western pharmacopeia must be created. Finally, a methodology for the study of drug use among prehistoric groups using ancient hair samples is described.     

Potential problems with the interpretation of hair analysis results

Due to differences in hair growth rate depending on anatomical region, age, gender, ethnicity and interindividual variability, interpretation of parent drug or/and metabolite concentrations in hair is not easy. Furthermore, as drug incorporation mechanisms into hair matrix is not yet fully understood, it is rather difficult to extrapolate details on time and dose from hair segment analysis. If incorporation sources other than from bloodstream (skin secretions and/or external/environmental contamination) are considered, interpretation becomes even more complicated. For evaluating possible passive contamination, it is essential to consider specific identification of metabolites, use of metabolite-to-parent drug ratios, assays of decontamination washes and analysis of specimens collected from other body parts. Cosmetic hair treatment, natural and artificial hair colour, differences in hair structure and specificity of analytical methodology may represent other bias sources affecting concentrations of drugs in hair. A suitable cut-off level related to the LOD will allow correct identification of drugs or metabolites in hair. Regarding the performance of different hair testing laboratories, little information is available at this time to what extent test results are comparable and their interpretation is consistent. Frequency of drug consumption and time intervals between multiple consumption or lag time between consumption and appearance in the hair has not been fully investigated and needs further research.     

Evaluation of two immunoassay procedures for drug testing in hair samples

A preliminary initial enzyme-linked immunosorbent assay (LUCIO-Direct ELISA kit) and a preliminary DRI enzyme immunoassay were evaluated for drug detection in head hair with respect to lowered cutoff values recommended in Germany for the control of abstinence in cases of re-granting of drivers' licences. Following drug classes were included: cannabinoids, opiates, cocaine like substances, amphetamine, methamphetamine (and methylenedioxyamphetamines), methadone, and benzodiazepines. 759 analyses were performed using LUCIO-Direct ELISA kits and 936 analyses using DRI enzyme immunoassay tests. Sample size for each drug group and immunoassay test reached from 74 to 178. The LUCIO-Direct ELISA kit revealed a sensitivity of 91% for amphetamine up to 98% for methadone (methamphetamine 92%, cocaine 94%, opiates 94%, benzodiazepines 96%) and values of specificity of 72% for methadone up to 89% for amphetamine and benzodiazepines. The test was not useful for a preliminary screening for tetrahydrocannabinol (sensitivity of 65%) in consideration of a suggested cutoff of 0.02 ng/mg. The DRI enzyme immunoassay test was only useful for morphine and cocaine testing at low recommended new cutoff values (0.1 ng/mg) revealing sensitivities of 94% and 99%, respectively.     

Evaluation of the catalytic decomposition of H2O2 through use of organo-metallic complexes--a potential link to the luminol presumptive blood test

Hair testing for drugs of abuse is performed in Lombardy by eleven analytical laboratories accredited for forensic purposes, the most frequent purposes being driving license regranting and workplace drug testing. Individuals undergoing hair testing for these purposes can choose the laboratory in which the analyses have to be carried out. The aim of our study was to perform an interlaboratory exercise in order to verify the level of standardization of hair testing for drugs of abuse in these accredited laboratories; nine out of the eleven laboratories participated in this exercise. Sixteen hair strands coming from different subjects were longitudinally divided in 3-4 aliquots and distributed to participating laboratories, which were requested to apply their routine methods. All the participants analyzed opiates (morphine and 6-acetylmorphine) and cocainics (cocaine and benzoylecgonine) while only six analyzed methadone and amphetamines (amphetamine, methamphetamine, MDMA, MDA and MDEA) and five Δ(9)-tetrahydrocannabinol (THC). The majority of the participants (seven labs) performed acidic hydrolysis to extract the drugs from the hair and analysis by GC-MS, while two labs used LC-MS/MS. Eight laboratories performed initial screening tests by Enzyme Multiplied Immunoassay Technique (EMIT), Enzyme-linked Immunosorbent Assay (ELISA) or Cloned Enzyme Donor Immunoassay (CEDIA). Results demonstrated a good qualitative performance for all the participants, since no false positive results were reported by any of them. Quantitative data were quite scattered, but less in samples with low concentrations of analytes than in those with higher concentrations. Results from this first regional interlaboratory exercise show that, on the one hand, individuals undergoing hair testing would have obtained the same qualitative results in any of the nine laboratories. On the other hand, the scatter in quantitative results could cause some inequalities if any interpretation of the data is required.     

Evaluation of the One-Step ELISA kit for the detection of buprenorphine in urine, blood, and hair specimens

A solid-phase enzyme immunoassay involving microtiter plates was recently proposed by International Diagnostic Systems corporation (IDS) to screen for buprenorphine in human serum. The performance of the kit led us to investigate its applicability in other biological matrices such as urine or blood, and also hair specimens. Low concentrations of buprenorphine were detected with the ELISA test and confirmed by HPLC/MS (buprenorphine concentrations measured by HPLC/MS: 0.3 ng/mL in urine, 0.2 ng/mL in blood, and 40 pg/mg in hair). The intra-assay precision values were 8.7% at 1 ng/mL of urine (n = 8), 11.5% at 2 ng/mL in serum (n = 8), and 11.5% at 250 pg/mg of hair (n = 8), respectively. The immunoassay had no cross-reactivity with dihydrocodeine, ethylmorphine, 6-monoacetylmorphine, pholcodine, propoxyphene, dextromoramide, dextrometorphan at 1 and 10 mg/L, or codeine, morphine, methadone, and its metabolite EDDP. A 1% cross-reactivity was measured for a norbuprenorphine concentration of 50 ng/mL. Finally, the immunoassay was validated by comparing authentic specimens results with those of a validated HPLC/MS method. From the 136 urine samples tested, 93 were positive (68.4%) after the ELISA screening test (cutoff: 0.5 ng/mL) and confirmed by HPLC/MS (buprenorphine concentrations: 0.3-2036 ng/mL). From the 108 blood or serum samples screened, 27 were positive (25%) after the ELISA test with a cutoff value of 0.5 ng/mL (buprenorphine concentrations: 0.2-13.3 ng/mL). Eighteen hair specimens were positive (72%) after the screening (cutoff: 10 pg/mg) and confirmed by LC/MS (buprenorphine concentrations: 40-360 pg/mg). The ELISA method produced false positive results in less than 21% of the cases, but no false negative results were observed with the immunological test. Four potential adulterants (hypochloride 50 mL/L, sodium nitrite 50 g/L, liquid soap 50 mL/L, and sodium chloride 50 g/L) that were added to 10 positive urine specimens (buprenorphine concentrations in the range 5.3-15.6 ng/mL), did not cause a false negative response by the immunoassay.     

Proficiency test for the analysis of hair for drugs of abuse,organized by the Society of Hair Testing

Eighteen laboratories interested in the analysis of human hair for drugs of abuse participated in a proficiency test (PT) organized by the Society of Hair Testing (SoHT) in 2001.Samples sent to the participants included one drug-free hair sample and two samples from drug users, sent in the form of short segments previously checked for homogeneity by three reference laboratories. Participants were requested to analyze the samples following the standard procedure used routinely in their laboratories.The compounds present in the samples included opiates, cocaine and metabolite, cannabinoids and amphetamines. All the laboratories analyzed opiates, cocaine and benzoylecgonine (BE); only 10 analyzed amphetamines, and 9 cannabinoids. Various methods were used to extract drugs from the hair-enzyme treatment, acidic, basic and methanol extractions. All the laboratories employed GC-MS, with the exception of two which used GC-MS/MS and LC-MS/MS, respectively. Six laboratories performed initial screening tests by RIA, ELISA or EMIT.Results show that the laboratories performed well qualitatively, since they successfully identified all the analytes that they tested, with the exception of eight false results. However, the scatter of quantitative results was high.     

Analysis of pain management drugs, specifically fentanyl, in hair: application to forensic specimens

This article discusses the immunoassay screening of pain management drugs, and the mass spectrometric confirmation of fentanyl in human hair. Hair specimens were screened for fentanyl, opiates (including oxycodone), tramadol, propoxyphene, carisoprodol, methadone, and benzodiazepines and any positive results were confirmed using gas chromatography or liquid chromatography with mass spectral detection. The specific focus of the work was the determination of fentanyl in hair, since autopsy specimens were also available for comparison with hair concentrations. Using two-dimensional gas chromatography with electron impact mass spectrometric detection, fentanyl was confirmed in four of nine hair specimens collected at autopsy. The accuracy of the assay at 10 pg/mg was 95.17% and the inter-day and intra-day precision was 5.04 and 13.24%, respectively (n=5). The assay was linear over the range 5-200 pg/mg with a correlation of r(2)>0.99. The equation of the calibration curve forced through the origin was y=0.0053x and the limit of quantitation of the assay was 5 pg/mg. The fentanyl concentrations detected were 12, 17, 490, and 1930 pg/mg and the results were compared with toxicology from routine post-mortem analysis. The screening of pain management drugs in hair is useful in cases where other matrices may not be available, and in routine testing of hair for abused drugs.     

The U.S. Mandatory Guidelines for Federal Workplace Drug Testing Programs: current status and future considerations

The U.S. Department of Health and Human Services (HHS) drug testing standards were published in 1988 and revised in 1994, 1998, and 2004. In 2004, significant revisions defining, standardizing, and requiring specimen validity testing on Federal employee donor urine specimens were included. In a separate notice, HHS proposed to establish scientific and technical guidelines for the Federal Workplace Drug Testing Program to: (1) permit laboratory testing of hair, oral fluid, and sweat patch specimens in addition to urine specimens for marijuana, cocaine, phencyclidine, opiates (with focus on heroin), and amphetamines [including methylenedioxymethamphetamine (MDMA), methylenedioxyethamphetamine (MDEA), methylenedioxyamphetamine (MDA)]; (2) permit use of on-site point of collection test (POCT) devices to test urine and oral fluid at collection sites; (3) permit use of instrumented initial test (screening only) facilities [IITF] to quickly identify negative specimens; and (4) add training requirement for collectors, on-site testers, and MROs. This proposal was published in the Federal Register on 13 April 2004, with a 90-day public comment period. The Substance Abuse and Mental Health Services Administration, HHS, reviewed those comments and is preparing the Final Notice that will define the requirements for such testing, including: specimen collection procedures, custody and control procedures that ensure donor specimen identity and integrity, testing facility, initial and confirmatory test cutoff concentrations, analytical testing methods, result review and reporting, evaluation of alternative medical explanations for presence of drug or metabolite in the donor's specimen, and laboratory certification issues. Voluntary pilot performance testing (PT) programs for each specimen type are on-going since April 2000 to determine how to prepare PT materials for specimens other than urine to evaluate laboratories' ability to routinely achieve accuracy and precision required. Certification programs will be developed using the current urine drug testing National Laboratory Certification Program model. The addition of accurate and reliable workplace drug testing using hair, oral fluid, and sweat patch specimens will complement urine drug testing, and aid in combating industries devoted to suborning drug testing through adulteration, substitution, and dilution. For example, hair testing may detect chronic drug use for up to 90 days and be useful in pre-employment situations; oral fluid testing may detect drug use in past hours and be useful in post-accident situations; sweat patch testing may be useful in follow-up drug testing and treatment programs; POCTs and IITFs may be most useful for quickly identifying specimens that are negative for drugs and indicate that the specimen is valid.     

Hair testing for drugs of abuse: evaluation of external cocaine contamination and risk of false positives.

In some laboratories hair testing may be the main method for the evaluation of individual's drug history, however, compelling evidence supports the possibility that the presence of a small amount of drug in hair can derive from external contamination. The aim of the present study is to verify if a single external contamination with a small amount of cocaine will last sufficiently long to make a contaminated subject indistinguishable from active users, and if normal washing practices together with the decontamination procedures are sufficient to completely remove the external contamination. The results obtained using the decontamination methods suggested in literature demonstrate that significant concentrations of cocaine (>1 ng/mg) and moderate quantities of benzoylecgonine (generally <0.5 ng/mg) are still detectable up to 10 weeks after contamination. These results question the reliability of hair testing. In fact, even using the most sophisticated decontamination procedures it is not possible to distinguish a drug-contaminated subject from an active user. Thus, while a negative result excludes both chronic use and "contact" with drugs, a positive result cannot and must not be interpreted as a sure sign of drug addiction, but should be further confirmed by urine analysis.