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.

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.

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.

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.

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.

Improved detection of ethyl glucuronide and ethyl sulfate in a pain management population using high-throughput LC-MS/MS

BACKGROUND

Ethyl glucuronide (EtG) and ethyl sulfate (EtS) have been proposed as markers for detecting alcohol use because they exhibit extended excretion lifetimes when compared with ethanol; however, their presence is not considered as absolute proof of alcohol use. Two methods are currently used for the detection and quantitation of EtG: immunoassay and mass spectrometry. The purpose of this study was to provide more patient data to better compare the two methods.

METHODS

A retrospective diagnostic accuracy study was performed to compare the methods. EtS was also measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS) as an additional comparative analyte. The investigators examined 4,287 sequential urines from pain patients to determine the incidence of alcohol use and the corresponding presence of EtG by immunoassay at a cutoff of 500 ng/mL. EtG and EtS were subsequently quantitated in all the urines using LC-MS/MS.

RESULTS

A total of 794 samples were found positive by immunoassay, and these results were compared at three distinct LC-MS/MS cutoffs of 100, 500, and 1,000 ng/mL. The incidence of ethanol use in this population was found to be at least 12 percent.

CONCLUSIONS

Approximately 30 percent of the samples screened by immunoassay as positive were confirmed to be negative by LC-MS/MS.

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.

Marijuana correlates with use of other illicit drugs in a pain patient population

BACKGROUND

A significant number of chronic pain patients may use marijuana. Physicians treating those patients can benefit by knowing whether their patients using marijuana are at higher risk for using other illicit drugs such as cocaine and/or methamphetamine.

OBJECTIVE

Our objective was to determine whether marijuana-using chronic pain patients have a higher incidence of cocaine and/or methamphetamine use.

STUDY DESIGN

A retrospective study of the incidence of pain patients using marijuana and/or other illicit drugs such as methamphetamine and cocaine versus the incidence of pain patients not using marijuana but using methamphetamine and/or cocaine.

METHODS

Urine specimens from chronic pain patients were analyzed by LC-MS/MS to determine the co-occurrence of these abused substances.

RESULTS

In this study 21,746 urine specimens were obtained from chronic pain patients. We found a 13.0% incidence of patients positive for the acid form of Tetrahydrocannabinol (THCA). The percentage of those positive for cocaine was 4.6%, those positive for methamphetamine totaled 1.07%. Using both chi-square and a Logistic Regression analysis, we determined that there was a correlation between marijuana use and the use of other illicit drugs. The odds ratio was > 3.7 for other illicit drug use.

LIMITATIONS

The study is limited in that we obtained no data as to the causal relationships of this type of drug use.

CONCLUSIONS

Pain physicians should be aware that this relationship exists and marijuana-using patients are at greater risk for use of other illicit drugs although no causal relationship is implied. Increased monitoring of these patients may help minimize potential morbidity due to drug interactions as well as identify patients who may be diverting prescriptions in order to pay for illicit drugs.

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.

Comparison of clonazepam compliance by measurement of urinary concentration by immunoassay and LC-MS/MS in pain management population

BACKGROUND

Physicians determine patient compliance with their medications by use of urine drug testing. It is known that measurement of benzodiazepines is limited by immunoassay specificity and cutoff limits and therefore does not offer physicians an accurate picture of their patients' compliance with these medications. A few studies have used lower cutoffs to demonstrate patient compliance.

OBJECTIVES

To define more appropriate cutoffs for compliance monitoring of patients prescribed clonazepam as determined using immunoassay and liquid chromatography-tandem mass spectrometry (LC-MS/MS).

STUDY DESIGN

A diagnostic accuracy study of the urinary excretion of clonazepam.

METHODS

Millennium Laboratories performed measurements on the urinary excretion of pain patients prescribed clonazepam as the indicator test. This benzodiazepine was chosen because it forms one major metabolite, 7-aminoclonazepam which is specific for that drug. Patients whose only benzodiazepine medication was clonazepam were selected as the test population. The Millennium Laboratories test database was filtered first to select patients on clonazepam, then a second filter was used to eliminate patients with any other listed benzodiazepine medications. Samples were tested using the Microgenics DRI benzodiazepine assay with a 200 ng/mL cutoff. The same samples were quantitatively assessed for 7-aminoclonazepam by LC-MS/MS with a cutoff of 40 ng/mL. The results from the immunoassay were scored as positive or negative while the quantitative results from the LC-MS/MS were also scored as positive or negative depending upon their concentration.

RESULTS

Samples from 180 patients met these medication criteria. The positivity rates were 21% (38 samples) by immunoassay. The positivity rate was 70% (126 samples) if the LC-MS/MS cutoff was set at 200 ng/mL. However, the positivity rate was 87% (157 samples) if the LC-MS/MS was set at 40 ng/mL. Concentration distributions revealed a significant fraction (7%) in the 40 - 100 ng/mL range.

LIMITATIONS

A limitation of the study was the inability to measure lower than 40 ng/mL. There may be another fraction of the population that was positive below the cutoff value.

CONCLUSIONS

The difference in positivity rate between the immunoassay and the LC-MS/MS result showed that the nominal 200 ng/mL cutoff of the immunoassay did not apply to 7-aminoclonazepam. This low immunoassay positivity rate is inconsistent with the manufacturer's published cross reactivity data for clonazepam and 7-aminoclonazepam. These data illustrate the limitations of using a 200 ng/mL cutoff to monitor clonazepam compliance and suggest that a cutoff of 40 ng/mL or less is needed to reliably monitor use of this drug.