Accurate 24-h urine cystine quantification for patients on cystine-binding thiol drugs.

Cystinuria is a rare disorder resulting in development of recurrent kidney stones, adversely affecting patient quality of life. The goal of cystinuria management is to reduce stone formation by increasing cystine solubility in urine, which includes lowering the urinary cystine level below its solubility limit. Treatment usually involves alkalinization of the urine and often requires initiating pharmacotherapy with a cystine-binding thiol drug (CBTD) such as tiopronin; however, proper dose adjustment requires accurate measurement of urinary cystine. The goal of this study was to validate a novel high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) method for quantification of cystine in the urine of patients with cystinuria receiving a CBTD. Urine samples were collected over 24 h from 24 patients and separated into 2 aliquots. Chromatographic separation of samples was conducted and separation of cystine from the cysteine-tiopronin drug complex was complete in < 3 min. The method was validated for accuracy, precision, linearity, limit of detection (LOD), and limit of quantification (LOQ). Mean accuracy range was 97.7-102.3%; intermediate precision was high with relative percent difference values calculated at 1.2-9.3%; the calibration curve resulted in a linear response throughout the concentration range (R2 = 0.998); and the LOD and LOQ were 0.002 and 0.005 mg/mL, respectively. Mean (range) cystine concentrations measured were 111.10 (51.31-179.46) and 242.21 (61.14-741.80) g/L in Aliquots A and B, respectively. The HPLC-MS/MS method presented here indicates that urine cystine can be reliably quantified in patients receiving a CBTD.

The Relationship Between Occupational Demands and Well-Being of Performing Artists: A Systematic Review.

Background: Performing artists are exposed to a range of occupational demands from organisational, interpersonal and intrapersonal sources, which may impact their well-being. The aim of this systematic review was to evaluate and synthesise the literature where researchers have considered the relationship between occupational demands and well-being in performing artists. Methods: A mixed-methods systematic review was conducted including professional and student performing artists. Quantitative, qualitative and mixed-methods study designs were eligible for inclusion in the review. A total of 14 databases were searched from their inception through to October 2017, including MEDLINE, EMBASE, and Scopus. Critical appraisal was conducted using the Mixed-Methods Appraisal Tool and results presented as a narrative synthesis. Results: A total of 20 studies were included in the review, comprising of quantitative (n = 7), qualitative (n = 9) and mixed-methods (n = 4) study designs. Several frameworks of occupational stress and well-being were explored in relation to the results. Organisational, social and emotional demands were associated with lower well-being. Conversely, music-making, performance activities and social support were reported to be resources and were related to higher well-being. Conclusion: This systematic review highlights the need for researchers in this field to adopt methodologically robust study designs, which are informed by appropriate theoretical frameworks. The paucity of high quality and theoretically informed research in this area is a hindrance to the development of evidence-based interventions for this population.

Positivity rates of drugs in patients treated for opioid dependence with buprenorphine: A comparison of oral fluid and urine using paired collections and LC-MS/MS.

BACKGROUND: Drug testing is recommended as part of comprehensive monitoring for medication-assisted treatment. Alternative matrices including oral fluid offer a number of advantages when compared with conventional urine testing but are not as well characterized. This study aims to compare positivity rates of drugs and drug classes in oral fluid and urine as a measure of the clinical utility of oral fluid in the evaluation and treatment of patients with opioid use disorders. METHODS: A retrospective review of paired oral fluid and urine test results from Millennium Health's laboratory database was performed for 2746 patients with reported prescriptions for buprenorphine products used in the treatment of opioid dependence. Specimens were tested using quantitative LC-MS/MS for 34 medications, metabolites and illicit drugs. RESULTS: A number of medications and illicit drugs were detected at comparable or higher rates in oral fluid vs. urine such as cocaine (15.7% vs. 7.9%), opiates (13.4% vs. 10.0%), oxycodone (8.6% vs. 3.7%), hydrocodone (3.0% vs. 1.2%) and others. Lower detection rates were observed in oral fluid vs. urine for benzodiazepines (6.6% vs. 8.7%), cannabinoids (15.5% vs. 19.5%), oxymorphone (1.8% vs. 3.1%) and hydromorphone (0.8% vs. 4.5%). CONCLUSIONS: Clinicians may find oral fluid advantageous for detection of specific drugs and medications in certain clinical situations. Understanding the relative differences between urine and oral fluid can help clinicians carefully select tests best suited for detection in their respective matrix. To our knowledge, this is the largest inter-matrix patient comparison study using paired collections and direct to definitive testing.

Detection of Hydrocodone and Morphine as Metabolites in Oral Fluid by LC-MS/MS in Patients Prescribed Codeine.

A retrospective analysis of oral fluid drug testing results using LC-MS/MS was performed to determine the prevalence rates in oral fluid for codeine (COD) and 3 COD metabolites-morphine (MOR), norhydrocodone (NHC), and hydrocodone (HCOD). Oral fluid samples were collected using Quantisal oral fluid collection device (Immunalysis Inc.) and submitted to Millennium Health, LLC for the routine drug analysis by LC-MS/MS. Consistent with previously published literature, COD was the primary analyte detected in oral fluid after the use of COD. In COD-positive samples, HCOD, MOR, and NHC were detected at rates of 68.4%, 18.4%, and 6.3%, respectively. Concentration ranges of these analytes were 1.0 to >2000 ng/mL for COD, 1.0-20.2 ng/mL for MOR, 1.0-740.0 ng/mL for HCOD, and 2.1-47.5 ng/mL for NHC. In contrast to urine, where HCOD is typically detected as a minor metabolite of COD, HCOD was the most commonly detected metabolite in oral fluid in samples testing positive for COD with reported prescriptions for COD. This observation suggests that care should be taken when interpreting HCOD positives in oral fluid results, and that the use of COD should be considered as one possible explanation for HCOD positives.

Differentiating medicinal from illicit use in positive methamphetamine results in a pain population.

In addition to illicit methamphetamine, there are prescription and over-the-counter medications that, if ingested, may yield positive methamphetamine (MAMP) results on laboratory urine drug tests. The purpose of the study is to estimate the prevalence of medicinal and illicit MAMP in the pain population using chiral analysis to determine the relative amounts of the d and l-MAMP enantiomers. This retrospective analysis included the LC-MS/MS results and prescriber provided medication histories of 485,889 de-identified urine specimens from patients treated for pain. Two groups of 100 specimens each were subjected to chiral analysis. Group 1 contained specimens that were MAMP positive and amphetamine negative. Group 2 contained randomly selected MAMP positive specimens. The overall MAMP positivity rate of the 485,889 specimens tested was 1.6%. The prevalence of MAMP medications based on reported medications and detection of l-MAMP in Group 1 and Group 2 was 44% and 6%, respectively. These data indicate that the use of both illicit and medicinal MAMP is found in this patient population, and that medicinal use is underreported in clinical histories. Therefore, clinical laboratories should provide on request chiral analysis to aid in differentiating illicit and medicinal MAMP.

Stability of pain-related medications, metabolites, and illicit substances in urine.

BACKGROUND: Effective urine drug testing requires an understanding of the stability of medications, metabolites and other substances excreted in the urine matrix. When the testing results do not fit the clinical picture, physicians frequently request repeat testing of the original specimen in order to corroborate the results. We determined the stability in urine of various medications, metabolites, and illicit substances commonly requested for testing by physicians treating patients with pain and pain-related disorders. METHODS: Quantitative analyses of urine specimens were performed using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Two replicates at a high and low concentration were analyzed at time 0, and after 2, 3 and 6 months following storage at +4 °C and -20 °C. At each time interval, the percent difference from time 0 for each analyte was calculated and averaged for each storage condition. RESULTS: For the majority of medications, the percent differences were within 20% of the original measurement for all 3 storage conditions. All were within 30% of the original measurement after 2, 3 and 6 months in all storage conditions, except for 7-amino-clonazepam, and carboxy-tetrahydrocannabinol. CONCLUSIONS: The findings from the current study confirm that the majority of medications, metabolites, and illicit substances commonly requested for testing by physicians treating patients with pain and pain-related disorders are stable within 20% of the original concentration when stored refrigerated or frozen for up to 6 months. Thus, delayed testing, repeat testing, and add-on testing of urine specimens can yield reliable results for up to 6 months following the urine collection date.

Illicit drug use correlates with negative urine drug test results for prescribed hydrocodone, oxycodone, and morphine.

BACKGROUND: A number of studies indicate that 10.8%-34% of patients with chronic pain use illicit drugs. One hypothesis for this occurrence is that some patients may be supplementing their prescription medications with illicit drugs. OBJECTIVE: The primary purpose of this retrospective data analysis was to test the hypothesis that people whose urine specimens are positive for the medications that have been listed as being prescribed to them are positive for fewer illicit substances than those whose specimens were negative for their prescribed medications. The secondary purpose of the study was to correlate the use of illicit drugs and the amount of prescribed medications excreted in urine. STUDY DESIGN: A retrospective study of the incidence of patients using illicit drugs versus their consistency with reported medications. METHODS: Using urine specimens from a cohort of nearly 400,000 patients whose identities had been redacted, and who were being treated for chronic pain with opioid therapy, this study was performed to correlate the patients' positivity with their prescribed medication to the prevalence of illicit substance use. A secondary study was conducted to correlate the amount of prescribed medication excreted in urine (measured in ng/mL) with the incidence of illicit drug use. The specific prescription medications analyzed were hydrocodone, morphine, and oxycodone. RESULTS: Specimens defined as negative for prescribed hydrocodone (27.3%), morphine (11.5%) or oxycodone (19%) were more likely to contain illicit drugs than those found to be positive for the prescribed medication. The illicit drug prevalence among the inconsistent specimens was 15.3% for hydrocodone, 23.8% for morphine, and 24.4% for oxycodone. The secondary study showed no statistically significant difference in the excretion level of prescribed medication between those patients using and not using illicit drugs. LIMITATIONS: The study is limited in that no data was obtained to determine the causal relationships of illicit drug use. CONCLUSIONS: This work supports the hypothesis that people who are positive for their prescribed medications use fewer illicit drugs than those who do not take their medications. It may be beneficial for physicians to test more thoroughly for illicit drugs when patients' drug tests are negative for their prescribed medications.

Therapeutic monitoring of benzodiazepines in the management of pain: current limitations of point of care immunoassays suggest testing by mass spectrometry to assure accuracy and improve patient safety.

BACKGROUND: Concomitant use of opioids and benzodiazepines can result in significant untoward effects. Point of care (POC) urine testing devices are commonly used tools to monitor patient use of medications. These useful devices are relatively inexpensive and yield immediate results that can be acted upon at the time of the appointment, although numerous limitations have been identified for specific medications or medication classes. We established the diagnostic accuracy of a commonly used POC testing method for benzodiazepines. METHODS: One thousand patients, from a single interventional pain practice receiving opioid therapy provided urine specimens as part of the usual practice of monitoring consistency with prescribed medications. These de-identified urine specimens were tested using LC-MS/MS and the results were compared using the standard calculations for sensitivity, specificity, and predicted value. Five specimens were excluded from the study because the prescribed flurazepam could not be confirmed by LC-MS/MS (the LC-MS/MS instrumentation was not set to identify flurazepam), resulting in 995 specimens. RESULTS: Point of care assays yielded false negative results for patients prescribed benzodiazepines nearly 20% of the time (98 out of 498 patients). The point of care cup often failed to produce positive results for persons who were shown by LC-MS/MS to be taking lorazepam or clonazepam. Although only 26 out of 498 patients (5%) were prescribed ≥2 benzodiazepines, 73 out of 498 patients (15%) were found to be positive for that drug class. CONCLUSIONS: POC immunoassay for benzodiazepines could fail to provide accurate information regarding patient specific medication use. The false positive and false negative rates of the immunoassay were particularly high for clonazepam and lorazepam. Further testing of patient specimens using more accurate methods such as LC-MS/MS is necessary to provide definitive data that can assist in clinical decision making, and potentially protect these patients from untoward effects, morbidity and mortality.

Determination of illicit drug cutoff values in a pain patient population.

BACKGROUND: When properly selected, cutoff levels minimize the reporting of false negative and false positive test results and allow the laboratory to accurately determine the prevalence of marijuana, cocaine and methamphetamine use. Selecting the ideal cutoff requires the collection of drug excretion data for a large patient population to determine the expected range of drug concentrations. The cutoff can then be set to capture a high percentage of positives at a concentration within the dynamic range of the method. We used quantitative urine drug excretion data to calculate cutoffs needed to best determine the presence of these illicit drugs in urine. METHODS: This study used liquid chromatography tandem mass spectrometry (LC-MS/MS) as the analytical method. The study group was the pain patient population which is well-known to have a significant incidence of use of these illicit drugs. Frequency distributions were plotted for the creatinine normalized and raw data for all positive specimens with values greater than or equal to the method limit of quantitation. A non-parametric 2.5% estimator was applied to each data set to establish the cutoff for each drug. RESULTS: The urinary excretion data for the three drugs studied suggest cutoffs of approximately 30 ng/ml (benzoylecgonine), 10 ng/ml (carboxy-THC), and 50 ng/ml (methamphetamine) to identify 97.5% of the users of these drugs in this population. CONCLUSIONS: Evaluation of urinary excretion data provides an objective method to validate the selection of cutoffs. These data provide additional support for the revised SAMHSA cutoffs which could increase the positivity rates for both benzoylecgonine and methamphetamine by 7%.

Determination of medication cutoff values in a pain patient population.

BACKGROUND: Clinical laboratories are required to establish reference intervals for all the analytes tested, and these are provided along with the test results. In contrast, laboratories testing for pain medications use cutoffs established by the manufacturers of immunoassay reagents. These cutoffs may be inappropriate for monitoring patients being treated for chronic pain with opioid therapy because the cutoffs are set too high. PURPOSE OF THE STUDY: To use quantitative urine drug excretion data determined by liquid chromatography-tandem mass spectrometry analysis to calculate cutoffs needed to best determine patient compliance with prescribed medications. METHODS: Two methods of calculation were used to estimate cutoffs. First, all positive results for each drug or drug metabolite were ranked from highest to lowest. The lowest value was one-half of the lower limit of quantitation. A nonparametric 2.5 percent estimator was used to establish each cutoff Second, positive results were normalized using creatinine values, resulting in the excretion being expressed as nanograms of excreted drug per gram of creatinine. A nonparametric 2.5 percent estimator was used to establish the cutoff. RESULTS: Cutoffs established using these calculations included at least 97.5 percent of the data for the drugs: 7-aminoclonazepam, alpha-hydroxalprazolam, buprenorphine, carisoprodol, hydrocodone, hydromorphone, meperidine, meprobamate, methadone, morphine, oxycodone, oxymorphone, propoxyphene, and tramadol gave cutoffs near the lower limit of quantitation. One exception was with the drug codeine, where the lower limit could not be identified. CONCLUSIONS: These cutoffs were significantly lower than those suggested by many immunoassay manufacturers and better identify patient compliance in a representative population of pain patients. The limitation of the study is that only values one-half of our lowest calibrator were used. By using population values, laboratories can establish appropriate cutoffs for best monitoring pain patient medication compliance.

Illicit drug use in the pain patient population decreases with continued drug testing.

BACKGROUND: A major concern of physicians treating pain patients with chronic opioid therapy and similar drugs is determining whether the patients are also using illicit drugs. This is commonly determined by urine drug testing (UDT). However, there are few studies on whether or not monitoring patients by this technique decreases illicit drug use. OBJECTIVE: To determine if the presence of illicit drugs decreases over a number of physician visits where UDT was performed. METHOD: The method involved a retrospective study of tests for the illicit drugs marijuana, cocaine, methamphetamine, ecstacy (MDMA) phencyclidine (PCP) and the heroin metabolite, 6-acetylmorphine as confirmed by Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS). A database of 150,000 patient visits was examined for the presence of any of these 6 drugs. RESULTS: A total of 87,000 patients were initially tested. The number of patients who were repeatedly tested decreased over time. The percentage of patients positive for any of these illicit drugs decreased from 23% to 9% after 14 visits where UDT was performed. When graphed there was a trend to decreasing use. The Spearman correlation = -0.88, p < 0.0001. The major illicit drug was marijuana. When this was removed from the analysis, there was an even greater correlation with decreased illicit drug use. Spearman correlation = -0.92 (p < 0.0001) using a weighted correlation. LIMITATION: Patients continuing to use illicit drugs might be dismissed from practices thus biasing the study towards illicit drug avoidance. CONCLUSION: Continued UDT might decrease illicit drug use among pain patients.

An improved method of determining ethanol use in a chronic pain population.

BACKGROUND: Determination of ethanol use in the pain patient population being treated with chronic opioid therapy is critically important to the treating physician. Urinary ethanol, ethyl glucuronide (EtG), and ethyl sulfate (EtS) have been used to identify alcohol use. Because urine samples are shipped to reference laboratories, the possibility of glucose fermentation during transit producing ethanol complicates interpretation. The purpose of this study was to establish whether ethanol-positive urine samples were due to ingestion or fermentation during shipping. METHODS: The authors obtained 94 ethanol-positive urine samples from pain patients, which were further tested for EtG, EtS, and glucose. RESULTS: Only 62 of the 94 samples contained EtS or EtS. Of the 94 samples, 63 samples had glucose values above 10 mg/dL. Four of the 32 EtG-negative patients had ethanol levels that were nonphysiologic. Limitations of the study include the lack of demographic data beyond treatment with opioids for chronic pain. CONCLUSIONS: Roughly one-third of the time, ethanol-positive urine samples that have been shipped were positive because of fermentation and not because of patient alcohol consumption. This method is a combination of urinary ethanol measurement and liquid chromatography tandem mass spectrometry quantitation of both EtG and EtS. In the absence of these metabolites, the presence of urinary ethanol is attributed to fermentation. The improvement is a better definition of the source of the ethanol. Confirmatory testing showing the presence of the ethanol metabolites EtG and EtS is needed to validate that the ethanol is due to consumption. The presence of glucose, while common in the ethanol-positive samples, is not an absolute indicator that the ethanol was due to fermentation.

Anomalous observations of hydrocodone in patients on oxycodone.

BACKGROUND: Urine drug monitoring is used by physicians treating chronic pain patients with opioid therapy. Patients are tested in part to insure that they are not taking other drugs. Therefore, the finding of hydrocodone in a patient who is only prescribed oxycodone has clinical implications. Oxycodone preparations are known to have small amounts of hydrocodone as an impurity estimated to be < 0.1%. We established the concentration of unexpected hydrocodone in patients taking oxycodone. METHODS: Urine drug testing specimens from a population of 30,000 pain patients prescribed oxycodone in various formulations were quantitatively measured using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The frequency and concentration of hydrocodone as a function of oxycodone concentration were determined. RESULTS: There were 187 specimens with > 100,000 ng/ml of oxycodone. Of these, 72% were positive for hydrocodone. Of the 311 specimens with oxycodone concentrations > 50,000-100,000 ng/ml, 33% were positive for hydrocodone. Of the 1067 specimens with oxycodone > 20,000-50,000 ng/ml, 16% were positive for hydrocodone. Of the 8508 specimens with oxycodone > 1000-20,000 ng/ml, 16% were positive for hydrocodone. CONCLUSIONS: The high frequency of hydrocodone in samples containing high concentrations of oxycodone was ascribed to the manufacturing process of the oxycodone medications. However, a significant number of patients also took hydrocodone that was not listed on their prescribed medications. When oxycodone is > 100,000 ng/ml, hydrocodone should be <1500 ng/ml. When oxycodone is < 100,000 ng/ml then hydrocodone should be <500 ng/ml. Values greater than these indicate non-prescribed hydrocodone use. Clinicians and laboratories testing urine for drugs should be aware of the possibility of low concentrations of hydrocodone in the urine of patients taking high doses of oxycodone.

Improvement of pain physicians' practices of opioid management: population-based urinary excretion data.

BACKGROUND: Physicians treating patients for chronic pain have limited means of determining whether a person is taking their medications as prescribed and are not taking extra medication. Complicating patient treatment regimens is the fact that pain physicians' prescribing practices may come under scrutiny by the Drug Enforcement Agency and other licensing agencies. If questioned, doctors can be hard-pressed to substantiate that their particular practices meet the established standard of care. It would be helpful to establish that their patients adhere to medications when compared with other practices. Previous studies show that urinary excretion data transformed by mathematical models can produce a reliable range of expected values for pain medications and may be useful to help resolve the aforementioned issues. PURPOSE OF THE STUDY: To provide comparative urinary excretion information data on three commonly prescribed opioid medications (morphine, hydrocodone, and oxycodone). METHODS: This retrospective study involved quantitative analysis of300, 000 urine specimens for three test drugs using previously described methods. The results were analyzed as percent frequency distributions and logarithmic functions. RESULTS: The authors established a creatinine-normalized range of urinary concentration values for each drug. Results for two practices were compared with the meta-findings, providing quantitative evidence of overall standard of care prescription practice by that physician. CONCLUSIONS: Expected urinary drug excretion values for morphine, hydrocodone, and oxycodone can potentially benefit pain physicians by showing that they are within the expected standard of care, helping to establish patient compliance, and identifying patients whose metabolism of these drugs may put them at risk.

Reference intervals: a novel approach to detect drug abuse in a pain patient population.

BACKGROUND: pain physicians have few objective ways of determining which of their patients are drug abusers. Traditionally, these include psychological tests, physical examination, patient history, and urine drug testing. The traditional urine drug testing information provided to pain physicians mainly identifies patient compliance or drug diversion with qualitative information, that is, the patient is positive or negative for the presence of the drug in excreted urine. Although this information is useful for establishing compliance and identifying diversion, it is incomplete because it does not identify drug abuse. OBJECTIVE: The authors endeavored to determine whether quantitative urine drug testing and mathematical estimators of the upper limits of excretion could be used to identify possible drug abusers. STUDY DESIGN: analysis of quantitative urine drug tests and application of mathematical models for reference interval estimation of common analytes to determine whether they could be used to define upper 9 7.5 percentile limits of excretion in the pain patient population. METHODS: the authors analyzed 8,971 consecutive urines from patients on chronic opioid therapy using nonparametric, parametric, robust, and transformed estimators to derive the upper 97.5 percentile concentration values of 31 drugs and their metabolites. RESULTS: the authors showed that the mathematical models used to define reference intervals could be applied to urinary drug excretion. As an example, an upper limit of excretion of approximately 100, 000 ng/mL was established for morphine. Limitations of the study included lack of information on medication history, time of last dose before urine collection, age, sex, and complete medical history. Better estimates of the upper limits of excretion can be obtained by physicians applying their knowledge of dosage and collection times. CONCLUSIONS: application of a reference interval model allows identification of a patient population that excretes extremely high amounts of drug or its metabolite when compared with the rest of the population. Explanations for this high excretion include high dosage medication by prescription and drug abuse, determination of which can be done by the treating physician. The authors suggest that this patent-applied-for analytical model can become a potential tool to alert physicians to patients who may be abusing drugs.

Observations of medication compliance by measurement of urinary drug concentrations in a pain management population.

BACKGROUND: One of the major concerns of physicians treating pain patients with opioids is to determine whether the patients are compliant, and this is commonly determined by urine drug testing. There is limited information on which drugs these patients are most compliant with. There is also limited information as to how compliance is defined in terms of cutoffs. OBJECTIVE: To compare reported patient medication use with the presence of the drug in the patients' urine with defined cutoffs. METHOD: A retrospective study of the medications listed by the physicians' offices and the confirmed drug test findings. A Millennium Laboratories database of 20, 457 patient results was examined for the presence of the listed medications and was matched for the presence of the drugs above the analytical cutoffs. RESULTS: For oxycodone and hydrocodone, the authors observed 23 and 24 percent noncompliance, respectively. For carisoprodol, they observed 33 percent noncompliance. For morphine, they observed 14 percent noncompliance. For methadone, they observed 9 percent noncompliance. CONCLUSIONS: Noncompliance is prevalent in this patient population and varies with the prescribed drug.

An evaluation of the diagnostic accuracy of liquid chromatography-tandem mass spectrometry versus immunoassay drug testing in pain patients.

BACKGROUND: Immunoassay screening is used by pain physicians to determine compliance with controlled substances. Because clinical use of pain medications is different from illicit drug use, there is a need to evaluate the level of diagnostic accuracy of this procedure for the pain patient. OBJECTIVE: To compare the results of automated screening by immunoassay with analysis by Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) in identifying pain patients using illicit drugs and pain patients excreting low concentrations of their prescribed medications. STUDY DESIGN: A diagnostic accuracy study. METHODS: Urine samples from 4,200 pain patients were tested by immunoassay and LC-MS/MS for the following drugs and metabolites: Amphetamine, Methamphetamine, Alpha-hydroxyalprazolam, Lorazepam, Nordiazepam, Oxazepam, Temazepam, Cannabinoids, Cocaine, Methadone, Methadone Metabolite, Codeine, Hydrocodone, Hydromorphone, Morphine, Propoxyphene, and Norpropoxyphene. RESULTS: In a number of patients negative immunoassay findings were superseded by positive results on analysis by Mass Spectrometry. These were termed false negative results. The greatest failures were for the benzodiazepines (28%) and for cocaine (50%). LIMITATIONS: The study was limited by the lack of complete demographics for the cohort and because only one immunoassay diagnostic product was used. It was also limited because not all drugs react the same in the immunoassay. CONCLUSIONS: We show that in general, immunoassay screening results are accurate, although as shown in this study there are many false negative observations. The use of LC-MS/MS technology significantly decreases the number of false negative results.