Detection of Neonatal Drug Exposure Using Umbilical Cord Tissue and Liquid Chromatography Time-of-Flight Mass Spectrometry

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1 ORIGINAL ARTICLE Detection of Neonatal Drug Exposure Using Umbilical Cord Tissue and Liquid Chromatography Time-of-Flight Mass Spectrometry Stephanie J. Marin, PhD,* Anna Metcalf, BS, Matthew D. Krasowski, MD, PhD, Brian S. Linert, MD, Chantry J. Clark, BS-ASCP(C), Frederick G. Strathmann, PhD,* and Gwendolyn A. McMillin, PhD* Background: A method for qualitative detection of 57 drugs and metabolites in umbilical cord tissue using liquid chromatography time-of-flight (TOF) mass spectrometry is described. Methods: Results from 32 deidentified positive specimens analyzed by an outside laboratory using screen with reflex to confirmation testing were compared with TOF results. In addition, 57 umbilical cord tissue specimens paired with corresponding chart review data and 37 with meconium test results were analyzed by TOF. Urine drug test results from mother (n = 18) and neonate (n = 30) were included if available. concentrations, recovery, and matrix effects were determined by analyzing fortified drug-free cord tissue and negative specimens. s (in nanograms per gram) ranged from 1 to 10 for opioids and opioid antagonists, 5 10 for benzodiazepines and nonbenzodiazepine hypnotics, for barbiturates, 8 for stimulants, and 4 for phencyclidine. Adequate sensitivity for the detection of cannabis exposure could not be realized with this method. Conclusions: Liquid chromatography time-of-flight mass spectrometry can provide accurate and sensitive detection of in utero drug exposure using umbilical cord tissue. Key Words: time-of-flight mass spectrometry, umbilical cord tissue, drugs of abuse, meconium, in utero drug exposure (Ther Drug Monit 2014;36: ) INTRODUCTION Babies exposed to drugs in utero can suffer from preterm delivery, neonatal withdrawal syndrome, and other long- and short-term health problems. Timely and accurate Received for publication April 16, 2013; accepted June 13, From the *ARUP Institute for Clinical and Experimental Pathology, and AR- UP Laboratories, Inc, Salt Lake City, Utah; Department of Pathology, University of Iowa Hospitals and Clinics, Iowa, Iowa; and Department of Pathology, University of Utah School of Medicine, Salt Lake City, Utah. Funding, instrumentation, and physical facilities were provided by the ARUP Institute for Clinical and Experimental Pathology and ARUP Laboratories, Inc. The authors declare no conflict of interest. Correspondence: Stephanie J. Marin, PhD, ARUP Institute for Clinical and Experimental Pathology, ARUP Laboratories, Inc, 500 Chipeta Way, Salt Lake City, UT ( stephanie.marin@aruplab.com). Copyright 2014 by Lippincott Williams & Wilkins detection of drug exposure helps clinicians and support staff to treat acute complications and develop a comprehensive treatment plan to maximize outcomes for these children. Meconium has become the specimen of choice for the detection of in utero drug exposure, but it has several limitations including matrix complexity, difficulties with collection, and a high incidence of insufficient sample volume. 1,2 Meconium can be expelled in utero during delivery, passage can be delayed in some infants, or become inadvertently or intentionally discarded and unavailable for testing. Other specimen types, including hair, urine, blood, sweat, oral fluid, nails, amniotic fluid, vernix caseosa, placenta tissue, and umbilical cord tissue have also been used to detect in utero drug exposure. 3,4 Notable differences exist in the ease of collection and in the detection utility of each specimen. The best-characterized alternate specimens are blood and urine, which represent a short detection window for drug exposure. Sweat, oral fluid, amniotic fluid, and vernix caseosa are also thought to represent recent drug exposure. Like meconium, hair, nails, and tissue (placenta and umbilical cord) are thought to represent exposure during the last trimester of pregnancy and may help to detect exposure during the second trimester. The major disadvantage of hair and nails is the limited amount of specimen available for testing at birth, making testing impracticable for most infants. Placenta and umbilical cord may offer an alternative specimen to meconium, with several distinct advantages. Recent studies with umbilical cord tissue suggest promising results that compare well with meconium. 4 9 Umbilical cord is readily available at birth, provides ample specimen for testing (a typical cord is approximately 22 inches long), and does not reflect drugs administered to the infant after birth. Specimens are traditionally screened by immunoassay to identify a drug class, followed by confirmation and quantitation by a more specific technique like gas chromatography mass spectrometry (GC-MS) or liquid chromatography tandem mass spectrometry (LC-MS/MS). This 2-step approach screen with reflex was originally developed to support workplace drug testing but may not be appropriate for clinical applications due to extended time to obtain results, inconsistencies between the screen and confirmation results, and discrepancies between the clinical history and expectations for results. 10 Inconsistencies in results are a consequence of differences in the specific drugs and metabolites present in Ther Drug Monit Volume 36, Number 1, February

2 Marin et al Ther Drug Monit Volume 36, Number 1, February 2014 a specimen type compared with those identified by various testing methods and the concentrations at which the compounds can be detected. When drugs are not detected by the screening method and confirmation testing does not occur, false-negative results are possible. One explanation for falsenegatives is reduced sensitivity of the immunoassay for the drug analyte of interest, as a consequence of lower crossreactivity for certain compounds (eg, drug metabolites) within a drug class. In contrast, if specimens screen positive but fail to confirm by mass spectrometry, it is assumed that the original result represents a false-positive. Apparent false-positives can be explained by drugs and metabolites for which there is immunoassay cross-reactivity but are not included in a confirmation panel. In addition, the presence of multiple drug analytes from a drug class in a specimen may exhibit sufficient cross-reactivity with the capture antibody for an immunoassay that, when summed, triggers a positive immunoassay result. However, when considered individually, the concentrations of the drug analytes may be too low to be detected by the confirmatory mass spectrometry assay. The screen with reflex approach also increases the time to result, which may contribute to excess hospital expense due to extended stays, and delay in appropriate treatment of the neonate. A final consideration is whether the quantitative values for confirmatory assays are useful for the interpretation of drug testing results obtained with meconium because few studies have demonstrated clear associations with concentrations and neonatal presentation or outcomes. A single, qualitative assay that identifies specific drugs and metabolites quickly and accurately would overcome the challenges of the existing paradigm, while still supporting the clinical reasons for testing. By detecting drug analytes that are aligned with clinical expectations, a new approach may improve utility of testing. We propose qualitative detection using liquid chromatography time-of-flight (TOF) mass spectrometry, detecting specific drugs and metabolites that are important for making neonatal management decisions. Our method applies accurate mass detection, at unique chromatographic retention times, to achieve sensitivity and specificity that approximates or exceeds most published confirmation methods. This test can be used as a stand-alone qualitative detection panel or can be better aligned with confirmatory testing when confirmation or quantitation is needed. Of note, this technology has been used to detect drugs in serum and plasma, 11 meconium, urine, and hair This is the first account we are aware of using TOF for analysis of in utero drug exposure by analyzing umbilical cord tissue. Although TOF is more costly than immunoassay, the cost of confirmation, sometimes requiring multiple tests for multiple drug classes, is comparable. Often, there is insufficient specimen to complete all comfiramtion testing, and confirmation testing delays time to result that could affect the treatment of affected neonates. The method described herein is TOF for compound identification. Cord tissue specimens previously analyzed by an outside laboratory (United States Drug Testing Laboratory, Des Plaines, IL) were analyzed by TOF, and the results were compared. In addition, cord tissues from the University of Iowa Hospitals and Clinics were also analyzed by TOF. Some of these cord specimens were paired with drug test results from meconium collected from the corresponding neonate, chart review data, and urine drug test results from mother and neonate if available. METHODS AND MATERIALS All standards were of 99% purity or better and purchased from Cerilliant (Austin, TX). All solvents were reagent grade or better and purchased from Thermo-Fisher Scientific (Waltham, MA) or VWR International (West Chester, PA). Type 1 water was generated using a Barnstead Nanopure Infinity ultrapure water system (Thermo Fisher Scientific). All other reagents and equipment are listed in our previously published method. 6 Cord specimens were rinsed with saline and patted dry. Slices of cord tissue (1 g) were homogenized, and 4 deuterated markers (morphine-d3, diazepam-d5, phenobarbital-d5, and benzoylecgonine-d5) at twice the cutoff concentration were added to each control and specimen. The samples were extracted in 2 ml of water with 0.1% Triton X-100 using a Bullet Blender (Next Advance, Averill Park, NY) and centrifuged at 149 g and 08C for 15 minutes. A 1 ml aliquot of the supernatant was loaded onto 1 ml of supported liquid extraction + columns (Biotage, Charlotte, NC) for supported liquid extraction following the manufacturer s instructions. The samples were eluted with two 2.5-mL fractions of ethyl acetate and 2-propanol in the ratio of 90:10. The eluate was dried under nitrogen at 408C using a Turbovap (Biotage) and reconstituted in 100 ml of 90:10 ratio of water and methanol for TOF analysis. Drug-free cord tissue was used to prepare positive and negative controls that were fortified at the cutoff concentration established for each analyte and run with every batch of specimens. Two controls were prepared, the contents ofwhichweredesignedtoseparateisobariccompounds.each positive control also served as a negative control for analytes in the opposite positive control. A unique negative control was also prepared and analyzed. An Agilent Technologies (Santa Clara, CA) 1260/6230 liquid chromatography TOF mass spectrometer equipped with a dual-spray Jet Stream electrospray ionization source, 2 Agilent binary pumps with G1379B vacuum solvent degassers, a 1260 series G1367D well plate autosampler, and a G1316B thermostatted column compartment with a 2-position 10-port switching valve was used. All samples were prepared and analyzed using our previously validated and published method 6 with the following changes: 2 Poroshell C 18 columns, mm, and 2.7-mm particle size (part number ; Agilent Technologies) were used with a flow rate of 0.5 ml/ minute and slight gradient modifications. The TOF data were collected in positive and negative ionization modes separately. Sensitivity was determined by analyzing spiked samples of drug-free cord at different concentrations. s were established based on the achievement of defined performance criteria (chromatography, mass accuracy, isotope abundance and spacing, and area counts). Recovery and ion suppression were evaluated by analyzing 5 unique drugfree specimens, and 2 sets of the same 5 specimens: one spiked at the cutoff concentrations at the beginning of sample preparation and another set spiked at the cutoff concentrations after sample preparation before dry down. Qualitative 120 Ó 2014 Lippincott Williams & Wilkins

3 Ther Drug Monit Volume 36, Number 1, February 2014 TOF Detection of Drugs in Umbilical Cord Tissue TABLE 1. Drugs and Metabolites in TOF Assay With Concentrations Drug Class/ Compound Unique Metabolites Barbiturate Amobarbital 40 Butalbital 40 Phenobarbital* 20 Secobarbital 40 Benzodiazepine Alprazolam 5 Alpha-hydroxyalprazolam 5 Clonazepam 5 7-Aminoclonazepam 5 Diazepam 5 Nordiazepam* 5 Flunitrazepam 5 7-Aminoflunitrazepam 5 Flurazepam 5 2-Hydroxyethylflurazepam 10 Desalkylflurazepam 5 Lorazepam 5 Midazolam 5 Alpha-hydroxymidazolam 5 Nitrazepam 5 Oxazepam* 5 Temazepam* 5 Triazolam 5 Alpha-hydroxytriazolam 5 Nonbenzodiazepine Hypnotic Zolpidem 10 Zopiclone 10 Stimulant Cocaine 8 Benzoylecgonine 8 Cocaethylene 8 m-hydroxybenzoylecgonine 8 Methamphetamine* 8 Amphetamine* 8 MDMA 8 MDA* MDEA 8 Phentermine 8 Hallucinogen Phencyclidine 4 Opioid Buprenorphine 2 Buprenorphine-3-8 glucuronide Codeine 6 Fentanyl 1 Heroin 6-Monoacetyl-morphine 4 Hydrocodone* 6 Dihydrocodeine* 4 Hydromorphone* 4 Meperidine 2 Methadone 10 EDDP 10 Morphine* 4 Oxycodone 4 Oxymorphone* 4 Propoxyphene 10 Norpropoxyphene 10 Tapentadol Tramadol 2 O-Desmethyltramadol 2 N-Desmethyltramadol 2 TABLE 1. (Continued) Drugs and Metabolites in TOF Assay With Concentrations Drug Class/ Compound Unique Metabolites Opioid antagonist Naloxone 8 Naltrexone 8 *Could be a metabolite of another drug. Not specifically detected. EDDP, 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine; MDA, 3,4-methylenedioxyamphetamine; MDEA, 3,4-methylenedioxyethamphetamine; MDMA, methylenedioxymethamphetamine. accuracy of results was determined from the evaluation of spiked samples, as well as through comparison of results obtained with 2 sets of authentic residual clinical specimens. One set comprised 32 specimens previously analyzed by an outside laboratory (United States Drug Testing Laboratory). This laboratory uses a screen with reflex to confirmation approach with enzyme-linked immunosorbent assay (ELISA) for screening and GC-MS or LC-MS/MS for confirmation and quantitation. These patient specimens were deidentified using a University of Utah Institutional Review Board approved protocol after test results from the outside laboratory were reported. The second set of samples comprised 57 cord tissue specimens that were collected and deidentified by the University of Iowa Hospitals and Clinics using an Institutional Review Board approved protocol. These specimens were paired with results of a detailed medical chart review, which included maternal self-report and pharmacy records. In addition, 37 of these cords were paired with drug test results obtained from meconium that was collected from the corresponding neonate. Urine drug test results from mother (n = 18) and neonate (n = 30) were included if available. Meconium testing was performed by ELISA with reflex to GC-MS or LC-MS/MS using previously validated College of American Pathologists 15 and Clinical Laboratory Improvement Amendments compliant methods in our laboratory. RESULTS Drug analytes detected by this method and established cutoffs are listed in Table 1. Thirty of the 32 specimens analyzed by the outside laboratory were positive for at least 1 drug analyte, and compounds detected by the outside laboratory (total of 42 positive results) were found using the TOF assay. These results are summarized in Table 2. TOF also found 64 positive results not detected by the outside laboratory. A subset of these drug analytes was not included in the outside laboratory s assay, whereas some were included but not found by the outside laboratory. Nineteen of these results were metabolites of previously detected compounds, further increasing the credibility of results. Twenty-one of these new results were verified by the presence of expected parent metabolite patterns in the TOF data, and the remaining 24 were detected without metabolites or the metabolites were not included in this assay. Ó 2014 Lippincott Williams & Wilkins 121

4 Marin et al Ther Drug Monit Volume 36, Number 1, February 2014 TABLE 2. Comparison of TOF Results to Outside Laboratory Drug or Metabolite Concentration * Detected by Both Laboratories Additional Compounds Detected by TOF Neg 2 Methamphetamine Amphetamine 5.3 to Benzoylecgonine 2.4 to.10 3 Cocaine 1 m-oh- 1 Benzoylecgonine Codeine 3 Hydrocodone 3.5 to Dihydrocodeine 7 Morphine 8.5 to Hydromorphone 2 to Oxycodone 8.1 to Oxymorphone 3.1 to Methadone.20 5 EDDP 7 to Fentanyl 2 Meperidine.20 1 Tramadol 2 N-Desmethyltramadol 1 Norpropoxyphene 2 Alprazolam 5.4 to Alpha-OH-alprazolam 3 Clonazepam 2 7-Aminoclonazepam 3 Diazepam Nordiazepam Oxazpam 1 Temazepam 1 Midazolam Alpha-OH-midazolam Zolpidem 7 Total *Concentrations reported by outside laboratory. Compounds confirmed by outside laboratory and detected by TOF. Drugs and metabolites detected by TOF not reported by the outside laboratory. Compounds not included in outside laboratory assay. EDDP, 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine. Considering the sample set that originated from the University of Iowa Hospitals and Clinics, 47 of the 57 cord specimens (27 with meconium results) had negative meconium and cord tissue results. Associated maternal and neonatal urine test results, where available, were also negative for drugs. Of the remaining 10 specimens, all had meconium results, and some had associated postnatal urine results. Results for the 10 positive specimens are summarized in Table 3. Three meconium samples were positive for opioids, whereas 2 had positive meconium results for a cannabinoid metabolite not detected by the currently described TOF assay. One of these mothers and one of these neonates (not related) also had positive urine results for cannabinoids. One of the positive opioid results also had neonatal urine that was positive for opioids, but the maternal urine results were negative. Four specimens that had negative meconium results were positive by TOF for fentanyl and zolpidem, consistent with the maternal pharmacy history but not included in the meconium or urine testing. In addition, 1 specimen was found by cord to contain both diazepam and oxycodone consistent with a maternal history of prescriptions for both of these drugs. These drugs were included but not found in the meconium and urine testing methods, suggesting that TOF and/or umbilical cord was more sensitive in this scenario. DISCUSSION The work presented here demonstrates that a 1-step approach to drug testing provided a similar degree of sensitivity and specificity to the traditional 2-step screen with reflex approach. Importantly, the TOF test was designed to specifically detect parent drug and metabolites when possible. Of the 64 additional positive results found by TOF, 19 results were metabolites of previously detected compounds (Table 2). Twenty-one of the additional positive results missed by the outside laboratory were compounds with consistent parent metabolite patterns. For example, amphetamine and methamphetamine were detected in 1 specimen, clonazepam and 7-amino-clonazepam were detected in 2 specimens, and diazepam and nordiazepam were detected in 1 specimen. Tramadol and N-desmethyltramadol were detected in one specimen, whereas codeine and hydrocodone in another. Two specimens had hydrocodone and dihydrocodeine, as well as 1 with codeine and hydromorphone was also present. In addition, 1 specimen had codeine, hydrocodone, and hydromorphone. The remaining 24 additional analytes found by TOF and missed by the outside laboratory met all of the TOF criteria, but either metabolites were not included in the TOF assay or were not detected. Seven positive results for zolpidem and 3 results for nordiazepam were found by TOF. Morphine, fentanyl, oxycodone, norpropoxyphene, and midazolam were detected in 2 specimens each (10 specimens total). Alprazolam, 7-aminoclonazepam, tramadol, and hydrocodone were each detected in 1 specimen (4 specimens total). Based on the TOF criteria for compound score, the results of the spiked samples used in the determination of sensitivity and matrix-matched positive and negative controls analyzed with each batch of specimens, the results from compounds detected by both methods, and those from the compounds where metabolite patterns were detected, we believe that the 24 additional single positive results are valid. The presence or absence of metabolites could be due to the concentration of drugs in the tissue, which is affected by the time, duration, or length of exposure of the fetus to a specific drug. Unfortunately, the incorporation of drugs and metabolites in cord tissue is not well understood at this time. From this work, it seems that dihydrocodeine is readily detected in cord tissue specimens with neonatal exposure to hydrocodone, as are most of the major benzodiazepine metabolites, in addition to cocaine and m-oh-benzoylecgonine with benzoylecgonine. However, this was a small cohort of specimens and more work needs to done before the incorporation, retention, and recovery of drugs in cord tissue are fully understood. The ability to evaluate the data 122 Ó 2014 Lippincott Williams & Wilkins

5 Ther Drug Monit Volume 36, Number 1, February 2014 TOF Detection of Drugs in Umbilical Cord Tissue TABLE 3. Meconium- Cord Tissue Positive Results ID Meconium Results Cord Results Urine Results (Mom) Urine Results (Neonate) Chart Review 55 Morphine 2 ng/g, codeine 72 ng/g Morphine, codeine Negative Opioids Acetaminophen/codeine 1 d before birth 35 Morphine 87 ng/g, oxycodone 5 ng/g Morphine, oxycodone Negative Negative 25 Negative Diazepam, oxycodone Negative Not performed Had prescriptions for both but no documented use in pregnancy. Clinical suspicion of prescription drug abuse 31 Negative Fentanyl Negative Negative Fentanyl for procedure 1 d before birth 56 Negative Zolpidem Not performed Not performed Zolpidem 2 d before delivery 61 Negative Zolpidem Not performed Negative Zolpidem 1 d before delivery, previous oxycodone prescription 53 Negative Zolpidem Negative Negative Zolpidem 1 d before 29 Hydrocodone 17 ng/g, hydromorphone 19 ng/g, dihydrocodeine present, codeine 135 ng/g, oxycodone 2 ng/g, oxymorphone 8 ng/g Negative Negative Negative History of illicit drug use, including prescription drug abuse 32 9-Carboxy-cannabis 485 ng/g NA Not performed Positive for cannabis 37 9-Carboxy-cannabis 190 ng/g NA Two specimens Negative positive for cannabis NA, marijuana exposure is not detected by this assay. Marijuana use in pregnancy Marijuana use in pregnancy for expected metabolite patterns greatly increases the credibility of the results; however, single results that meet TOF criteria should not be discounted based on the absence of metabolites. The results of the cord and paired meconium cord tissue specimens with chart review yielded a total of 7 positive neonates. One neonate (ID No. 29) had positive meconium results for 6 opioids, but the corresponding cord tissue was negative by TOF. Maternal and neonatal urine results were also negative. Two had positive meconium and cord/tof results (patient numbers: 35 and 55). Patient number 55 was positive for morphine and codeine in both specimens, and chart review records indicated that codeine had been administered to the mother 1 day before birth. Urine results were negative. Patient number 35 had morphine and oxycodone present in meconium and cord tissue. Maternal urine testing was not performed, but neonatal urine results were positive for opioids. Five neonates had negative meconium results but positive cord tissue/tof results and had evidence in the chart review to support the TOF results (neonate numbers: 25, 31, 53, 56, and 61). Three mothers had been administered zolpidem before delivery, and their babies had cord tissue positive for zolpidem (patient numbers: 53, 56, and 61). One mother had received fentanyl for a procedure 1 day before delivery, and fentanyl was detected in the cord tissue (patient number: 31). Diazepam and oxycodone were detected in 1 cord tissue specimen where the mother had prescriptions for both, but no use during pregnancy was indicated. Urine testing for these 5 specimens was negative or not performed (Table 3). Based on the results of patients (numbers 35 and 55), at least some of the drugs found in the meconium of patient number 29 should have been detected in cord tissue. The correlation and distribution of drugs and metabolites in either specimen type and how they compare is not well understood, and exact time windows for the detection of drugs are also not well known. The discrepant results could be due to multiple factors originating from the time, duration and amount of exposure, and differences in drug incorporation between the 2 specimen types. These results also indicate that drugs administered just before delivery can be detected in both specimen types. Careful chart review and patient histories should be evaluated to help distinguish prescription use or medical administration of drugs from illicit use. Moreover, drugs administered to the neonate after birth could be detected in meconium; however, the analysis of cord tissue would eliminate this concern. CONCLUSIONS In a single assay, qualitative analysis by TOF detected more than twice as many positive results when compared with traditional screen with reflex testing by an outside laboratory. TOF provides a method for drug detection that meets or exceeds typical confirmation cutoffs and offers superior sensitivity and specificity compared with ELISA with confirmation by mass spectrometry, with the exception of marijuana exposure in umbilical cord tissue. This qualitative assay can provide reliable detection of drugs and metabolites with a single method using only 1 g of specimen and a reduced turnaround time. The ability to evaluate parent metabolite pairs greatly increases the credibility of results. Ó 2014 Lippincott Williams & Wilkins 123

6 Marin et al Ther Drug Monit Volume 36, Number 1, February 2014 ACKNOWLEDGMENTS The authors thank Jennifer Williams and Lisa Norris for extracting the cord tissue patient specimens. Also, the authors M. D. Krasowski and B. S. Linert thank the University of Iowa Hospitals and Clinics obstetrics inpatient services staff (Amy N. Sanborn, manager) for assistance with the umbilical cord collection protocol. REFERENCES 1. Gareri J, Klein J, Koren G. Drugs of abuse testing in meconium. Clin Chim Acta. 2006;366: Moore C, Negrusz A, Lewis D. Determination of drugs of abuse in meconium. J Chromatogr B Biomed Sci Appl. 1998;713: Moller M, Gareri J, Koren G. A review of substance abuse monitoring in a social services context: a primer for child protection workers. Can J Clin Pharmacol. 2010;17:e177 e Gray T, Huestis M. Bioanalytical procedures for monitoring in utero drug exposure. Anal Bioanal Chem. 2007;388: Montgomery DP, Plate CA, Jones M, et al. Using umbilical cord tissue to detect fetal exposure to illicit drugs: a multicentered study in Utah and New Jersey. J Perinatol. 2008;28: Montgomery D, Plate C, Alder SC, et al. Testing for fetal exposure to illicit drugs using umbilical cord tissue vs meconium. J Perinatol. 2006; 26: Buchi KF, Fau-Suarez C, Suarez C, et al. The prevalence of prenatal opioid and other drug use in Utah. Am J Perinatol. 2013;30: Concheiro M, Jones HE, Johnson RE, et al. Umbilical cord monitoring of in utero drug exposure to buprenorphine and correlation with maternal dose and neonatal outcomes. J Anal Toxicol. 2010;34: de Castro A, Diaz A, Pineiro B, et al. Simultaneous determination of opiates, methadone, amphetamines, cocaine, and metabolites in human placenta and umbilical cord by LC-MS/MS. Anal Bioanal Chem. 2013; 405: Mikel C, Almazan P, West R, et al. LC-MS/MS extends the range of drug analysis in pain patients. Ther Drug Monit. 2009;31: Marin SJ, Hughes JM, Lawlor BG, et al. Rapid screening for 67 drugs and metabolites in serum or plasma by accurate-mass Lc-TOF-MS. J Anal Toxicol. 2012;36: Guale FSS, Walterscheid JP, Chen HH, et al. Validation of LC TOF-MS screening for drugs, metabolites, and collateral compounds in forensic toxicology specimens. J Anal Toxicol. 2013;37: Crews BO, Pesce AJ, West R, et al. Evaluation of high-resolution mass spectrometry for urine toxicology screening in a pain management setting. J Anal Toxicol. 2012;36: Ristimaa J, Gergov M, Pelander A, et al. Broad-spectrum drug screening of meconium by liquid chromatography with tandem mass spectrometry and time-of-flight mass spectrometry. Anal Bioanal Chem. 2010;398: Chan D, Caprara D, Blanchette P, et al. Recent developments in meconium and hair testing methods for the confirmation of gestational exposures to alcohol and tobacco smoke. Clin Biochem. 2004;37: ERRATUM 13 th International Congress of Therapeutic Drug Monitoring & Clinical Toxicology, Grand America Hotel, Salt Lake City, Utah, USA, September 22 26, 2013 In the abstracts that appeared on page 657 of the October 2013 issue, the title of the meeting at which they were presented was omitted. The title should read: 13 th International Congress of Therapeutic Drug Monitoring & Clinical Toxicology, Grand America Hotel, Salt Lake City, Utah, USA, September 22 26, 2013 REFERENCE 1. Pharmacogenetics: Tacrolimus. Ther Drug Monit. 2013;35(5): Ó 2014 Lippincott Williams & Wilkins