A case series evaluation of comprehensive drug testing in the pediatric acute care setting

Highlights

• •Demonstration of the utility of real-time comprehensive drug testing for acute care pediatric cases.
• •Results, when negative, rule-out toxic exposure, allowing for investigation into alternative causes of symptoms.
• •Results, when positive, lead to appropriate medical and social interventions.
• •Results inconsistent with medical history were determined to be due to accidental ingestion of prescribed medication or an illicit substance.

Abstract

Introduction

Drug testing typically follows a one-size-fits-all approach that is inadequate in some clinical scenarios, such as child maltreatment, neglect, and unintentional drug exposure. Results from immunoassay-based testing, which are non-specific, insensitive, and far from comprehensive, can lead to unintended consequences for children and their families.

Objectives

The objective of this retrospective case series study is to evaluate the utility of real-time (0–1 day) comprehensive drug testing as an alternative to immunoassay-based testing in the pediatric acute care setting.

Methods

Comprehensive drug testing results obtained by mass spectrometry testing and associated medical data for all pediatric cases (0–12 years) at one institution from 2019 to 2022 were included in the analysis. The final case series (n = 7) included all cases from patients <3 years with comprehensive drug testing results that were inconsistent with medication history and/or toxicology results by immunoassay.

Results

Comprehensive drug testing by mass spectrometry was ordered for 174 urine and blood samples representing 97 patients (0–12 years) from 2019 to 2022. Of these, 76 cases were from patients <3 years old; results were consistent with medication history and confirmatory for immunoassay results (n = 34), consistent with medication history (n = 14), confirmatory for immunoassay results (n = 10), negative (n = 9), or medical history was incomplete (n = 2). The remaining 7 cases were included in the final case series.

Conclusions

The cases highlight the value of real-time comprehensive drug testing in acute pediatric cases. Testing results can rule out toxic exposure from the diagnostic differential when negative, and lead to appropriate medical and social interventions when positive.

Introduction

According to the United States National Poison Data Center, there are more than 800,000 pediatric (<5 years old) substance exposures reported to American Poison Centers annually, accounting for 41% of all cases [1]. Over-the-counter, illicit, and pharmaceutical drugs account for the majority of substances involved in pediatric fatalities [1]. Exposures causing death in this age group are mostly coded as “unintentional” [1]. These numbers do not account for unreported exposures that require no medical intervention or exposures that require medical intervention but are not managed in collaboration with a poison center. Even in cases requiring acute medical care, toxic exposures can go unrecognized without the use of testing methodologies that allow for definitive identification of toxic substances.

In the United States, drug testing in clinical settings typically follows a screen and confirm approach. Urine samples are tested for common illicit drugs and prescribed medications with potential for misuse, using Federal Drug Administration (FDA)-approved immunoassay-based methods. While these tests can be performed rapidly, results are only considered presumptive since they are prone to both false-positive and false-negative results [2], [3], [4]. Confirmatory testing using mass spectrometry (MS) is needed for definitive drug identification [5]. There are no FDA-approved confirmatory drug tests; all confirmatory drug testing is done by laboratory-developed tests (LDTs) that are developed, validated, and maintained by a single clinical laboratory. Most LDTs for confirmatory drug testing utilize liquid chromatography tandem mass spectrometry (LC-MS/MS).

Confirmatory drug testing allows for definitive drug identification, but there are still limitations in the setting of acute exposure. Confirmatory tests are targeted and only capable of detecting the drugs and metabolites they are designed to detect. The combination of immunoassays and targeted LC-MS/MS confirmation methods do not detect all drugs and metabolites of clinical interest. Additionally, confirmatory methods are not available in all clinical laboratories, requiring most laboratories to send confirmatory testing to a larger reference laboratory, resulting in a longer turn-around time from sample collection to result. Testing is typically done in batches at scheduled testing intervals, adding to the delay in obtaining results.

In the setting of acute pediatric drug exposure, the screen and confirm approach has many limitations. The limited scope and speed of testing does not allow for detection of all potential toxic substances, and results are not obtained in time to impact patient management. A false-positive or false-negative screening result with a delayed confirmatory test can have significant consequences for patients and their families. Alternative approaches, such as direct LC-MS/MS testing bypassing immunoassay screening, have been described [6]. In some clinical settings, comprehensive drug tests that are capable of detecting a variety of toxicologically relevant substances in biological fluids are available for the evaluation of poisoned patients. In recent years, the utilization of liquid chromatography high resolution mass spectrometry (LC-HRMS) for comprehensive drug testing has been described [7], [8], [9], [10], [11], [12]. In contrast to targeted LC-MS/MS confirmatory methods, LC-HRMS methods are designed to acquire data in an untargeted manner, allowing for sensitive and specific identification of a broad range of drugs and metabolites. This retrospective case series study aims to evaluate the utility of real-time (0–1 day) comprehensive drug testing using LC-HRMS in the pediatric acute care setting. Real-time LC-HRMS comprehensive drug tests are currently not offered in most clinical laboratories; more research is needed to determine the impact these LDTs have on patient management and to provide justification for more widespread availability.

Methods

All comprehensive drug testing was conducted using liquid chromatography high resolution mass spectrometry (LC-HRMS) with a clinically validated assay as an LDT. The analytical method and criteria for positive drug and metabolite identification have been previously published [11], [13], [14], [15], [16]. Briefly, urine samples were diluted 1:5 with mobile phase and serum/plasma samples underwent protein precipitation, centrifugation, dry-down with nitrogen gas, and reconstitution in mobile phase. Testing can be performed on as little as 50 μL of sample, which is advantageous for pediatric testing. Chromatographic separation was achieved using a Kinetex C18-column with a 10-minute gradient from 2% to 100% organic. Data was collected on a SCIEX TripleTOF®5600 operating in positive-ion mode using a time-of-flight MS survey scan with information dependent acquisition triggered collection of high-resolution product ion spectra (20 dependent scans). Data review was done using PeakView and MasterView software (SCIEX, Redwood City, CA) using a targeted library containing 325 drugs and metabolites of clinical interest. This method is used as a standalone clinical test for definitive identification of drugs and metabolites, and in some cases serves as a confirmatory method for urine toxicology immunoassay screening tests for pediatric cases.

For this study, we conducted a retrospective chart review of comprehensive drug testing for acute (emergency department or inpatient) pediatric cases (ages 0–12) within the University of California San Francisco (UCSF) Hospital System from 2019 to 2022. This study was approved by the UCSF Institutional Review Board, and a waiver of informed consent was granted since the retrospective research could not be carried out without the waiver. Case information was obtained from electronic medical record review. For the focused case series, cases were excluded if the child was >3 years of age, and the comprehensive drug testing results were 1) negative, 2) consistent with prescribed medications or history of over-the-counter (OTC) drug administration, or 3) confirmatory for the urine toxicology screen by immunoassay. The urine toxicology screen included immunoassays for amphetamines, barbiturates, benzodiazepines, cannabinoids, cocaine, methadone, opiates, and oxycodone. The test manufacturer for these assays varied by ordering hospital. An immunoassay for fentanyl was added to each hospital laboratory’s urine toxicology screen at different times during the study period.

Results and discussion

Fig. 1 contains a flowchart for case series inclusion. Comprehensive drug testing by LC-HRMS was ordered for 87 urine and 87 blood samples representing 97 pediatric patients, aged 0–12 years, from 2019 to 2022. There was a significant annual increase in cases during the study period, with 5 cases in 2019, 14 in 2020, 34 in 2021, and 44 in 2022. By comparison, there were 3,603 urine toxicology immunoassay screens ordered for the same age group during the study period. The average turn-around time from sample receipt in the laboratory to result was 1.1 days, with 65% reported within 24 h; however, this average is skewed since the test is currently not run on weekends due to staffing limitations. The majority of the comprehensive drug testing cases (n = 92) originated from one pediatric trauma hospital. In all cases, the test was ordered to determine if the child’s acute symptoms were due to drug exposure. To narrow down the number of cases for the focused case series, those from children 3 years of age and greater were excluded (n = 21). Of the 76 cases for children <3 years of age, 67 were excluded because the comprehensive drug testing results were: 1) consistent with prescribed medications or OTC drug history and confirmatory for the urine toxicology screen by immunoassay (n = 34); 2) consistent with prescribed medications and OTC drug history (n = 14); 3) confirmatory for the urine toxicology screen by immunoassay (n = 10); or 4) no drugs or metabolites were detected (n = 9). For these excluded cases, there were 44 where the urine toxicology screen was positive and the comprehensive drug test provided confirmatory results. In these cases, the results also provided confirmation that the child was not exposed to additional drugs not detected by the urine toxicology screen. Among the excluded cases, there were 23 where the comprehensive drug testing results were negative or matched the patient’s medication history. While these results were considered negative, they informed patient care by allowing for the exclusion of a toxic exposure from the diagnostic differential. There were nine cases where the comprehensive drug testing results identified a drug or metabolite that was inconsistent with medication history and/or the urine toxicology immunoassay screen. Of these cases, two were excluded due to an incomplete medical history. The findings from the remaining seven cases are summarized below.

Fig. 1.

Flow diagram of pediatric cases included in the study. Prescription medication is abbreviated Rx and over-the-counter medications is abbreviated OTC.

Pediatric cases

A previously healthy 16-month-old female presented with rhinorrhea, diarrhea, abdominal distension, hypoglycemia, and a witnessed seizure on her way to the hospital. Two days prior, she had mild emesis but was otherwise in her normal state of health, with no history of hypoglycemia or seizures. She was afebrile with stable vitals and her initial blood glucose was 29 mg/dL. She was treated with a 25% dextrose injection. A respiratory virus panel was positive for rhinovirus/enterovirus and endocrinology was consulted to evaluate underlying metabolic or endocrine derangements. An exhaustive endocrine laboratory work-up was initiated. The urine toxicology screen by immunoassay was negative and comprehensive drug testing was requested to rule out unknown exposure to an anti-diabetic agent. The serum sample collected at the time of admission was positive for glipizide, a second-generation sulfonylurea that is FDA-approved for the treatment of adults with type 2 diabetes mellitus. It was later confirmed that the child’s grandfather was prescribed glipizide. The patient was weaned off dextrose-containing fluid and maintained appropriate blood glucoses. The endocrine service canceled all pending endocrine related tests and cleared the patient for discharge without any further recommendations for medical follow-up. In this case, comprehensive drug testing provided the answer for the unexplained hypoglycemic incident and allowed for discontinuation of a comprehensive endocrine laboratory work-up.

A previously healthy 22-month-old male was admitted to the pediatric intensive care unit for cardiac and neurological monitoring after being found at home somnolent on the floor next to an open bottle of Atorvastatin, a statin medication used to prevent cardiovascular disease and treat abnormal lipid levels. The child had been unmonitored at home for about two hours when his elderly legal guardian fell asleep while watching a show with him. On admission, the patient was hemodynamically stable but drowsy and bradycardic. Laboratory results were notable for compensated metabolic acidosis. Urine toxicology screening by immunoassay was negative. Electrocardiogram (EKG) results and computerized tomography (CT) scan of the head and x-ray of the chest and abdomen were all unremarkable. Poison control was contacted and recommended monitoring for bradycardia and hypotension, assuming that the patient had consumed Lipitor. Other medications reported to be in the home included gabapentin, amlodipine, Lasix, carvedilol, desipramine, amoxicillin, and ziprasidone. Comprehensive drug testing in urine and serum identified olanzapine, an atypical antipsychotic primarily used to treat schizophrenia and bipolar disorder. The primary symptoms of olanzapine overdose include central nervous system depression with somnolence, low blood pressure, respiratory depression, and anticholinergic effects. The patient returned to neurological baseline on hospital day three and was cleared for discharge. The inpatient social work team was involved in the case and referred the caregiver to child protective services for case follow-up and a discussion of potential support services for care of the child. Comprehensive drug testing identified a drug, olanzapine, that was not provided in the history but was consistent with the clinical presentation; this testing allowed for appropriate follow-up with child protective services.

A 10-month-old female with no significant past medical history was found at home with an unknown white powder on her face. Subsequently, the patient became irritable with mild tremors and jerking of the head and bilateral upper extremities. In the emergency department, the patient was afebrile and tachycardic with laboratory results notable for lactic acidosis. The patient tested positive for rhinovirus/enterovirus, and the urine toxicology screen by immunoassay was positive for amphetamines. An EKG was notable for a prolonged QTc interval. Poison control was consulted and recommended EKG monitoring every 6 h, lorazepam as needed for ongoing seizure activity, continued monitoring of lactate and creatine kinase, maintenance IV fluids, and a minimum 24-hour monitoring period. Comprehensive drug testing was ordered for urine and serum, which both were positive for bupropion, an atypical antidepressant primarily used to treat major depressive disorder, and hydroxybupropion, its primary metabolite. The patient’s grandmother had been prescribed bupropion, and the bottle had been stored within reach of the child in the home. The patient was monitored for 24 h after seizure activity ceased and was discharged on hospital day three. Of note, bupropion in high concentrations is known to cause a false positive amphetamine immunoassay result for some FDA-approved assays. The comprehensive drug test confirmed that the patient had not been exposed to methamphetamine; the symptoms were determined to be a result of an accidental ingestion of bupropion. As a result of the testing, no medical follow-up was required to assess for a potential seizure disorder.

A 20-month-old, previously healthy male presented via ambulance after being found unresponsive at home following a routine nap. He had a Glasgow Coma Scale (GCS) score of 3, low heart rate and severe lactic acidosis. The patient was intubated and placed on an epinephrine drip. The urine drug screen by immunoassay was negative. Empiric antimicrobial therapy was initiated for potential meningitis. Brain magnetic resonance imaging (MRI) findings were concerning for a metabolic or toxic process, such as 1) a mitochondrial disorder related to an asparyl-tRNA sythetase 2 (DARS2) mutation which causes an increase in serum lactate, 2) infectious cerebellitis, or 3) pediatric opioid-use-associated neurotoxicity with cerebellar edema syndrome (POUNCE). Urine and serum samples obtained on admission prior to intubation were sent for comprehensive drug testing and found to be positive for fentanyl and norfentanyl. At the time, the urine immunoassay toxicology screen did not include a test for fentanyl. The case was reported to child protective services, and it was noted that the child would have had a fatal outcome without urgent medical intervention. This case highlights the importance of adding a fentanyl immunoassay to urine immunoassay toxicology panels. In this case, opioid exposure was not suspected until it was indicated on the differential to explain the abnormal MRI findings. The urine immunoassay toxicology results were misleading; however, identification of fentanyl and norfentanyl by comprehensive drug testing allowed for the appropriate referral to child protective services. All genetic testing that had been ordered to test for a metabolic derangement was canceled, and no further medical follow-up was necessary.

A previously healthy two-year-old male was brought to the emergency department by his mother, concerned about his decreased responsiveness and lethargy over the past 24 h. He had no fever, upper respiratory symptoms, head trauma, or recent illness. The patient had severe bradycardia and altered mental status and was admitted to the hospital for close monitoring. The urine drug screen by immunoassay, head CT, comprehensive metabolic panel, aspirin, and acetaminophen levels were all normal. Medications in the house reported to be inaccessible to the child included omeprazole, metformin, atorvastatin, sumatriptan, and loratadine. Poison control was consulted and recommended comprehensive drug testing to help inform further care. Tetrahydrozoline was identified in the urine and serum; this is the active ingredient in eyedrops and some nasal sprays. It is an imidazoline with direct activity on peripheral alpha-1 adrenoreceptors. If ingested, it can cause decreased neurotransmitter release in the central nervous system leading to sedation, muscle relaxation, and analgesia; common symptoms include altered mental status, bradycardia, and respiratory depression. It was concluded that the patient’s symptoms were a result of ingestion of eye drops present in the household. Once stable, the patient was discharged without the need for further medical consultation.

A two-year-old female with a history of asthma and atopic dermatitis presented to the emergency department with a one-week history of cough, progressive somnolence, ataxia, and altered mental status. On admission, the patient was bradycardic, hypotensive, afebrile, lethargic, and had respiratory depression and mild bilateral wheezing. The patient tested positive for rhinovirus/enterovirus; however, all other labs were unremarkable, including a negative urine toxicology immunoassay screen. An extensive diagnostic workup was performed, including head CT, abdominal ultrasound, chest x-ray, and EKG; all of which were unremarkable. It was then suspected that the patient’s symptoms may be due to an acute toxidrome. Comprehensive drug testing was ordered and identified clonidine in the serum and urine. It was confirmed that the patient’s older sibling was prescribed clonidine to treat attention-deficit/hyperactivity disorder. The discharge diagnosis was accidental or unintentional ingestion of an anticholinergic drug. In this case, comprehensive drug testing provided the answer for the unexplained symptoms and allowed for hospital discharge without the need for medical follow-up.

A healthy 18-month-old male was difficult to arouse from his afternoon nap and was found to be short of breath, limp, and pale. His mother immediately took him to the emergency department, where he was unresponsive with a GCS score of 3. She reported that he had a cough and congestion for several days. The patient was acidotic and hypoxic with low oxygen saturations. He received one dose of naloxone, a medication used to reverse or reduce the effects of opioids, and showed an immediate response with rapid improvement in his breathing pattern and oxygen saturations. The urine toxicology immunoassay screen was negative; however, comprehensive drug testing of the same sample identified acetaminophen, benzoylecgonine, fentanyl, norfentanyl, and parafluorofentanyl. No serum was tested in this case. The mother was unsure what the child could have ingested and indicated that no medications or drugs were present in the household, although multiple people lived there. Given the concern for ingestion of a dangerous substance, a bone survey was conducted to evaluate for occult injury; no injuries were identified. Child Protective Services was notified to assess the safety of the home and to evaluate for other substances that may be available there. This case highlights the importance of adding a fentanyl immunoassay to urine immunoassay toxicology panels. Furthermore, the added sensitivity of the comprehensive drug test compared to immunoassays allowed for the detection of benzoylecgonine, a cocaine metabolite, in the patient’s urine, confirming exposure to cocaine. The detection of parafluorofentanyl, an illicit fentanyl analog, highlights the importance of monitoring for emerging novel psychoactive substances even in pediatric populations at risk for exposure.

Conclusions

In this case series, acute pediatric cases with comprehensive drug testing results that were not consistent with the patient’s medical history were all determined to be due to accidental ingestion of a family member’s medication or an illicit substance, primarily in the child’s home. In all but two cases, the history provided by the caregiver did not provide evidence for potential drug exposure. Comprehensive drug testing was ordered to determine if the child’s acute symptoms were due to drug exposure. Definitive identification of the causative drugs responsible for the child’s symptoms in all cases led to a change in patient management, ranging from discontinuation of medical care and the need for medical follow-up to appropriate reporting to child protective services during the child’s hospital stay. Even in these cases, the time from the test order to result was limited by the time it took to get the sample to the one centralized laboratory for testing. Regardless, in this case series, comprehensive drug testing provided answers while the child was still in the hospital that could not have been obtained using the screen and confirm two-step approach that is standard practice in the United States. This approach falls short of meeting the needs of some of our most vulnerable patients: children. Alternative approaches such as real-time comprehensive drug testing need to be considered. Additionally, only a small sample volume is required for comprehensive drug testing; a minimum of 50 μL, which is advantageous for pediatric testing and significantly less than what is required for screening and confirmation. This study was limited in scope to just pediatric acute care cases (<3 years old) and the conclusions cannot be generalized to all pediatric cases, particularly in an outpatient setting. Comprehensive drug testing should only be ordered when toxic exposure is on the diagnostic differential.

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.