Comprehensive toxicology screening in the emergency department: an aid to clinical diagnosis

Changes in Diagnosis of Poisoning in Patients in the Emergency Room Using Systematic Toxicological Analysis with the National Forensic Service

BACKGROUND

It is difficult to diagnose patients with poisoning and determine the causative agent in the emergency room. Usually, the diagnosis of such patients is based on their medical history and physical examination findings. We aimed to confirm clinical diagnoses using systematic toxicological analysis (STA) and investigate changes in the diagnosis of poisoning.

METHODS

The Intoxication Analysis Service was launched in June 2017 at our hospital with the National Forensic Service to diagnose intoxication and identify toxic substances by conducting STA. Data were collected and compared between two time periods: before and after the initiation of the project, i.e., from June 2014 to May 2017 and from June 2017 to May 2020.

RESULTS

A total of 492 and 588 patients were enrolled before and after the service, respectively. Among the 588 after-service patients, 446 underwent STA. Among the 492 before-service patients, 69.9% were diagnosed clinically, whereas the causative agent could not be identified in 35 patients. After starting the service, a diagnosis was confirmed in 84.4% of patients by performing a hospital-available toxicological analysis or STA. Among patients diagnosed with poisoning by toxins identified based on history taking, only 83.6% matched the STA results, whereas 8.4% did not report any toxin, including known substances. The substance that the emergency physician suspected after a physical examination was accurate in 49.3% of cases, and 12% of cases were not actually poisoned. In 13.4% of patients who visited the emergency room owing to poisoning of unknown cause, poisoning could be excluded after STA. Poisoning was determined to be the cause of altered mental status in 31.5% of patients for whom the cause could not be determined in the emergency room.

CONCLUSION

A diagnosis may change depending on the STA results of intoxicated patients. Therefore, appropriate STA can increase the accuracy of diagnosis and help in making treatment decisions.

Accuracy of current clinical diagnosis in recreational drug-related attendance to the emergency department

OBJECTIVE

To determine the accuracy of current clinical diagnosis in recreational drug-related attendances to emergency by blood analysis.

METHODS

A prospective convenience sample of 103 patients who attended hospital with suspected recreational drug-related presentations was collected. Doctors' clinical impression of drugs responsible for presentation was compared with a detailed forensic blood analysis for recreational drugs.

RESULTS

Among 103 samples, 80 (78%, 95% confidence intervals [CI] 70-86%) were found to have correct clinical suspicion of the recreational drug responsible for clinical presentation confirmed by laboratory analysis. Clinical diagnosis was most accurate for gamma-hydroxy butyrate (GHB) (sensitivity 97%, specificity 91%) and less accurate for amphetamines (sensitivity 61%, specificity 79%), alcohol (sensitivity 42%, specificity 84%) and opiates (sensitivity 46%, specificity 100%). Multiple drug ingestion was found in 70% (95% CI 61-79%) of samples. Sensitivity and specificity of clinical impression for prediction of multiple drug ingestion presence is 75% (95% CI 66-83%) and 85% (95% CI 78-92%), respectively.

CONCLUSION

Clinical diagnosis in recreational drug-related attendances to the ED was correct in most cases. Drugs, such as GHB, were the most accurately diagnosed. Inaccuracy in recognizing other drugs, like amphetamines, opiates and alcohol, occurs where a coingestant produces a more profound clinical picture. Multiple drug ingestion is a common scenario in recreational drug presentations to emergency.

Clinical assessment compared to laboratory screening in acutely poisoned patients

Acute poisonings may require identification of the toxic agents. It is impossible for routine laboratories to provide a full spectrum of toxicological analyses, and clinicians should know the reliability of the clinical diagnoses of toxic agents. We performed a 1-year study of hospitalized acute poisonings to determine the agreement between the clinical assessment on admission and serum laboratory tests for eight common toxic agents. Blood samples were drawn in 665 (70%) of the 947 admissions. The total number of laboratory found agents (967) exceeded the clinically suspected (871) by 11%. The agreement between the clinical assessment and laboratory analyses was good for ethanol and paracetamol ( κ = 0.70 for both), whereas only moderate or fair for other agents ( κ 0.22–0.51). Sensitivities of the clinical assessments compared to the laboratory results were better for common than rare agents, and better for higher than lower serum concentrations. The four most common agents (ethanol, benzodiazepines, paracetamol, and opiates) had overall sensitivity of 82% for higher-than-median serum concentrations, whereas the other agents had sensitivities ranging from 14% to 71% for higher-than-median concentrations. The reliability of the clinical diagnoses varied to such an extent that agents, which are important to recognize for specific treatment, should be tested for.

The approach to the patient with an unknown overdose

Toxic overdose can present with various clinical signs and symptoms. These may be the only clues to diagnosis when the cause of toxicity is unknown at the time of initial assessment. The prognosis and clinical course of recovery of a patient poisoned by a specific agent depends largely on the quality of care delivered within the first few hours in the emergency setting. Usually the drug or toxin can be quickly identified by a careful history, a directed physical examination, and commonly available laboratory tests. Once the patient has been stabilized, the physician must consider how to minimize the bioavailability of toxin not yet absorbed, which antidotes (if any) to administer, and if other measures to enhance elimination are necessary.

Comparison of Urinary On-Site Immunoassay Screening and Gas Chromatography-Mass Spectrometry Results of 111 Patients With Suspected Poisoning Presenting at an Emergency Department

On-site tests based on immunoassay techniques are widely used for toxicologic screening analysis in patients with suspected poisoning. However, such assays usually have been validated using urine samples with known concentrations of the investigated substances. In the present investigation, on-site screening results were evaluated in a clinical setting. This was a retrospective study of patients with suspected poisoning from January to December 2003 in the emergency department of a tertiary urban hospital. Urine samples were analyzed using the Triage 8 panel and gas chromatography-mass spectrometry (GC-MS). A total of 111 patients were included (54 female, 57 male; average age 37.8 +/- 19.7 years). A total of 3.8% of the patients showed no symptoms, 45.2% minor, 24.0% moderate, and 26.9% serious symptoms. In 50 patients (45.0%), Triage 8 results corresponded well with GC-MS results. In 17 patients (15.3%), the Triage 8 results were confirmed by GC-MS, but additional substances were determined that could not be detected by the Triage 8 panel. A completely negative Triage 8 screening result was obtained in 23 patients (20.7%) who showed toxicologically relevant findings in GC-MS. In 21 patients (18.9%), Triage 8 results could not be confirmed by GC-MS. The analysis of the results in view of the patients' medical histories revealed that in 20 patients (18.0%), no relevant toxic substance could be detected. Additionally, 8 patients (7.2%) showed intoxication with alcohol, which could not be detected by the presently applied toxicologic screening investigations. On-site screening results in suspected poisoning were not very helpful in the present study because practically every second patient ingested substances that were not detectable by the Triage 8 device. In addition, every fifth result was not in line with GC-MS findings. On-site test findings should be interpreted very carefully, and in critical cases, a GC-MS screening should be performed.

Clinical vs. laboratory identification of drugs of abuse in patients admitted for acute poisoning

OBJECTIVE

The extent of drug abuse in patients admitted for self-poisonings is uncertain. The aim of this study was to assess the pattern of drugs of abuse among patients admitted for acute poisoning according to age and gender, and to study the concordance between the clinical assessments by the physicians on duty and the drug analyses.

METHODS

Prospective cross sectional study of all patients (n = 405, 52% males, median age 31 years) treated for acute poisoning in our department during one year (2001). The physician on-call classified type of drug of abuse by history and clinical assessment. This was later compared to urine and blood samples analysed for ethanol, benzodiazepines, opiates, cocaine, ecstasy, GHB, amphetamine and cannabis.

RESULTS

In 320 admissions (79%), the comparison between clinical diagnosis and laboratory analyses could be performed. A total of 478 drugs were suspected and 621 were found. The main toxic agents found were benzodiazepines (49.7%), ethanol (40.3%), opiates (35.3%), cannabis (23.8%) and amphetamine (21.3%). Ninety-two had used drugs of abuse. The agreement between clinical assessments and laboratory findings was best for GHB and ethanol (kappa = 0.43), and for opiates (k = 0.38). For benzodiazepines and cannabis, the concordance was poor (k = 0.18 and 0.10, respectively). However, the correct clinical evaluation for these substances was 59% and 77%, respectively.

CONCLUSIONS

Drugs of abuse were more frequently found than suspected clinically. Benzodiazepines, ethanol and opiates were most common. The agreement between clinical assessment and drug analyses was moderate to low. Physicians seem to underestimate the use of these drugs.

Trends in alcohol- and drug-related ER and primary care visits, 1995-2000: are Healthy People 2000 objectives met?

Data were compared between the 1995 (n = 4925) and 2000 (n = 7612) National Alcohol Surveys to determine whether Healthy People 2000 objectives of a reduction in alcohol- and drug-related emergency room (ER) visits were met. Year of survey (2000) was positively predictive of drug use but not of alcohol use, prior to an event for which ER and other treatment were obtained. The data suggest Healthy People 2000 objectives were not met and in fact may be related to an increase in drug abuse among those seeking any kind of health services treatment, but not to an increase in drug use in general.

A combined HPLC-immunoenzymatic comprehensive screening for suspected drug poisoning in the emergency department

OBJECTIVE

To review the results of a comprehensive drug screening as first line diagnostic tool in patients attending an emergency department for suspected drug poisoning.

METHODS

A comprehensive drug screening was carried out in plasma or urine, or both, of 310 patients combining an HPLC multidrug profiling system and a fluorescence polarisation immunoassay.

RESULTS

In 64.2% of cases the screening confirmed the diagnosis of drug poisoning, in 13.9% suspected drugs were measurable at non-toxic concentrations, and in 21.9% no drugs were found. The suspected drugs were fully confirmed in a minority of cases, (symptomatic patients: 28.2% compared with asymptomatic: 16.5%). Symptomatic patients were less likely to have at least one suspected drug (29.6% compared with 57.7%; p<0.001), and more likely to have at least one unsuspected drug found at analysis (17.4% compared with 3.1%; p = 0.005). In 5% of patients, asymptomatic when first observed, one or more unsuspected drugs were found. In 6 of 29 patients, with suspected poisoning of an unspecified drug, the screening identified the specific drug and excluded acute intoxication in the remaining cases.

CONCLUSION

A rapid comprehensive drug screening adds to the diagnosis of patients with suspected drug poisoning, identifying unsuspected drugs in symptomatic patients and excluding drugs in asymptomatic subjects.

Position of immunological techniques in screening in clinical toxicology

There is a continuing increase in the use of immunological techniques in the field of clinical toxicology. This is primarily due to the rapidity by which analytical results are now required, and can be obtained, following the testing of individuals for drug use. There has recently been an increase in the repertoire of assays now available to testing laboratories (e.g., buprenorphine and heroin metabolite assays), with the techniques themselves becoming increasingly more specific for the drugs and/or metabolites being monitored (e.g., methadone metabolite assays). The near patient testing (NPT), or point-of-care testing (POCT), devices are now several generations forward from their inception, with some tests now approaching the sensitivity and specificity of automated laboratory-based methods. This review has been collated from the literature to illustrate some of the possible reasons for the move towards the increasing use of immunological techniques, and to highlight some of the advantages and disadvantages associated with such drug screening methods. In particular, it has been shown that it is important to determine, monitor and review the knowledge and training of the individual using the technique. In addition, quality control and quality assessment are paramount to ensure the validity of any drug testing being performed. It has also been shown that it is vital to maintain and develop the relationships between the staff performing the testing, the laboratory (if the testing is performed using NPT devices), and the clinicians utilising the results obtained from drug testing. Without these links, interpretive errors could arise which could adversely affect the diagnosis and management of patients.

Suspected Pediatric Ingestions: Effectiveness of Immunoassay Screens vs. Gas Chromatography/Mass Spectroscopy in the Detection of Drugs and Chemicals

Rapid and accurate analytical testing can be of great value when determining treatment for pediatric patients suspected of ingesting an unknown chemical. Though often overlooked, gas chromatography/mass spectroscopy (GC/MS) can be a valuable resource in emergency toxicology testing. In a recent 24-month period (July 1999-June 2001), the Analytical Toxicology Laboratory at the University of Mississippi Medical Center, Jackson, MS, compared the results of GC/MS analysis to results obtained by immunoassay testing. The laboratory tested 139 urine samples referred for STAT toxicology testing from the hospital's Pediatric Emergency Department. All samples were tested in parallel using an immunoassay technique (EMIT) and GC/MS. With analysis by immunoassay, 17.3% of the samples were positive for a drug of abuse. The number of positive drug classes ranged from 0 to 2 per sample (mean 0.17 +/- 0.43) using immunoassay. With analysis by GC/MS, drugs were detected in 88.5% of the samples. The number of drugs detected ranged from 0 to 11 per sample (mean 2.2 +/- 1.8) with GC/MS. A total of 64 different pharmaceuticals were identified by GC/MS. This study shows that analysis by GC/MS offers the clinician a more comprehensive view into the exposure of the pediatric patient presenting with an unknown chemical ingestion.

Comprehensive drug screening in decision making of patients attending the emergency department for suspected drug overdose

OBJECTIVES

This study aimed to evaluate the usefulness of a comprehensive drug screening method as a first line diagnostic tool on clinical decision making in patients attending an emergency department for suspected drug overdose in terms of agreement between physicians on patients' disposal.

METHODS

Five emergency physicians retrospectively evaluated the records of 142 adult patients, admitted to the emergency department of a community hospital for suspected drug overdose. They were asked for an expert opinion on patients' disposal at the end of the observation period, based on paired records, with/without the results of a comprehensive drug screening.

RESULTS

In the absence of the drug screening, a very poor agreement (kappa statistics) was observed between physicians. When the drug screening was available, the interobserver agreement for decision on patients' disposal increased to the fair to good range (global agreement: from 0.238 (0.019) to 0.461 (0.020) (mean(SE)); p<0.001). The agreement also increased when admission to an intensive care unit, to a general ward, and discharge from hospital were separately analysed. The availability of drug screening would have saved 21.7% of hospital admissions and 53.3% of high dependency and/or intensive care unit admissions.

CONCLUSION

Comprehensive drug screening adds to decision making for patients attending an emergency department for suspected drug overdose, improving agreement among physicians on patients' disposal and potentially saving hospital resources.

Decision rule and utility of routine urine toxicology screening of trauma patients

The objective of this study was to determine the impact of urine drug screening of major trauma victims on patient care and derive a decision rule for selective screening. Retrospective chart review of 170 trauma patients at a Level I Trauma Center, certified by the American College of Surgeons, was undertaken. The decision rule was developed by Classification and Regression Tree (CART) analysis to maximize sensitivity, with secondary attention to specificity. Eighty-nine percent of trauma patients were screened, while 26.0% had positive tests for illicit drugs. Serum ethanol was positive in 31.2%, over the legal limit of 0.08 g/dl. Both a legally intoxicated ethanol level and positive illicit drug screen were found in 11.0%. Additionally, 42.5% of patients with a positive illicit drug screen were also intoxicated (blood alcohol level above legal limit). Conversely, 35.4% of legally intoxicated patients also had positive illicit screens. Drug treatment referral occurred in 17.5% of positive drug screens. For urgent surgery, median time to drug screen result was 117 min, while median time to operation was 110 min. Of operative patients, 57% had the drug screen result recorded on the chart at any time, but only 14.3% of illicit screens were noted in the anaesthesia record. For all patients with and without operations, 71.1% had the result noted on the chart. We derived a 'low risk rule' to identify most patients with positive illicit drug screens (95% sensitivity, 55% specificity, 66% positive and 93% negative predictive values; accuracy 74%), while limiting the number of unnecessary tests. The rule avoids screening 48% of patients, missing only 5% of true positives. It is concluded that urine screening for illicit drugs in trauma patients can be performed selectively according to a decision rule based on demographics, mechanism of injury and time of presentation. This rule, which captures most positive screens while eliminating screening in low risk patients, could result in significant cost savings. Only prospective validation of these rules in patient populations of other trauma centres will offer confidence that the decision points are valid. Urine drug screening infrequently affected patient management or resulted in drug treatment referral in our sample. We call for increased vigilance in recording results and referring patients for treatment.

Identification of drugs ingested in acute poisoning: correlation of patient history with drug analyses

The aim of this study was to assess the reliability of patient history in the identification of the drugs taken by patients who have an acute drug overdose. To this end, a prospective study involving 51 cases of acute, deliberate drug poisoning was carried out (patients with ethanol as the only apparent cause of intoxication were excluded). Information based on interviews with the patients and their companions or on circumstantial evidence (e.g., drug containers found) was compared with the results from drug analyses of various body fluids. The information obtained on admission was completely in accordance with the laboratory findings in only 27% of the cases. Minor discrepancies between the history and the results from drug analyses concerning the identity of the drugs taken were found in 55% of the cases. In 18% of the cases, the discrepancies were considered clinically important. Serious symptoms occurred in approximately 20% of the patients, but none of them were the result of incorrect information obtained on admission. All the patients survived. These results support the prevailing view that rapid identification of the drugs taken in overdose by means of comprehensive drug screens would have little effect on the treatment of most cases of acute poisoning. However, such assays would enable optimal treatment of many cases of acute poisoning by reducing the need for supervision and costly treatments and facilitating the identification of cases that would require prompt drug-specific treatment.

Utility of comprehensive toxicologic screens in children

This study was undertaken to evaluate the clinical utility and cost-effectiveness of the limited component versus the high performance liquid chromatography (HPLC) component of comprehensive toxicologic screens in children. A retrospective patient series was studied at the emergency department (ED) of Hughes Spalding Children's Hospital, an urban, tertiary-care ED, consisting of all patients younger than 19 years of age who had a comprehensive toxicologic screen between January 1994 and July 1995. The comprehensive test included a broad-spectrum HPLC component as well as a limited component that examined serum for ethanol, aspirin, and acetaminophen and urine for benzodiazepines, barbiturates, amphetamines, cocaine, phencyclidine, and opiates. All toxicologic screens were reviewed for the presence of exogenous toxins, followed by a chart review of all patients with positive screens and a selection of negative screens. Toxins were categorized as (1) iatrogenic or noniatrogenic, (2) clinically or nonclinically suspected by history and physical, and (3) clinically or nonclinically significant. Comprehensive toxicology screens were performed in 463 cases during the study period; 234 (51%) were positive for exogenous toxins. In 227 of 234 positive screens (97%), toxins were either suspected by history and/or physical, were present on the limited portion of the toxicology screen, or were clinically insignificant. The remaining 7 of the 234 positive screens (3%) were clinically significant and detected solely by the broad-spectrum HPLC portion of the comprehensive screen. However, in none of these 7 cases was patient management clinically altered as a result of the positive screen. The total additional cost for the HPLC component was $16,205 ($35x463), an average distributive charge of $2,315 per patient in whom the HPLC portion provided additional clinical information ($16,205/7). Although adding significant charges to the evaluation of suspected toxic exposures in children, the HPLC component of the comprehensive drug screen was of no additional clinical benefit compared with its limited component alone.

Acetaminophen and salicylate serum levels in patients with suicidal ingestion or altered mental status

Is universal screening of acetaminophen (APAP) and salicylate (SAL) necessary in patients with a suicidal ingestion or an altered mental status and suspected ingestion? This descriptive, retrospective chart review in an emergency department in a large urban county hospital examined all patients who presented with a history of suicidal ingestion or an altered mental status with a strong suspicion of ingestion from January 1992 through October 1993. APAP and SAL serum levels were measured in 1,820 patients, and charts of patients with APAP serum levels of > 1 microgram/mL or SAL serum levels of > 1 mg/dL were reviewed. The patient's history of ingesting APAP or SAL was recorded, as well as the clinician's interpretation of that level. Sixteen charts were not available. APAP levels of > 1 microgram/mL were found in 175 (9.6%) patients, 120 (6.5%) of whom were APAP history-positive and 55 (3%) APAP history-negative. None of the APAP history-negative group required therapy with N-acetylcysteine. Eight (0.3%) of the APAP history-negative group had potentially toxic levels of > 50 micrograms/mL. SAL levels of > 1 mg/dL were found in 155 (8.5%) patients, 44 (2.5%) of whom were SAL history-positive and 111 (6%) SAL history-negative. Three patients were SAL history-negative but had a significant chronic SAL intoxication. All these patients presented with an altered mental status and had an anion gap of > 20 mEq/L. Universal screening found that 0.3% of suicidal ingestions had a potentially toxic APAP intoxication not suggested by history. This incidence of infrequent but potentially life: threatening overdose should prompt clinicians to screen all of their patients with a suspected ingestion. Salicylate screening found that 0.16% of suicidal ingestions had a toxic SAL intoxication not suggested by history, although such intoxication should be suggested by an elevated anion gap and an altered mental status. Since this less severe intoxication is less frequent and usually suggested by commonly obtained laboratory data, universal screening is not indicated, but a more selective approach to screening could be taken.

The underreporting of cocaine-related trauma: drug abuse warning network reports vs hospital toxicology tests

OBJECTIVE

The purpose of this study was to assess whether cocaine-related trauma is underreported to the US Federal Drug Abuse Warning Network (DAWN).

METHODS

We compared DAWN reports filed by an urban emergency department with the department's toxicology results for patients treated for major trauma. DAWN regulations in effect during the study period required the reporting of all patients treated for injury who used drugs or who tested positive for drugs of abuse.

RESULTS

Of 520 patients treated for major trauma, 217 (42%) were tested for a variety of drugs. Of these, 82 (38%) tested positive for cocaine. Of the 102 patients injured in motor vehicle accidents, 20 (20%) tested positive for cocaine. Of the 59 patients injured in motor vehicle accidents who were under age 40, 18 (30%) tested positive for cocaine. Of 100 victims of violent assault, 57 tested positive for cocaine. During the time period studied, DAWN recorded 48 hospital visits associated with cocaine, none involving trauma or injury.

CONCLUSIONS

Cocaine-related trauma was unreported to DAWN despite the hospital's compliance with the system's guidelines. The pattern of DAWN reports from other institutions suggests that underreporting of cocaine-related injury is widespread.

Toxicology screening of the trauma patient: a changing profile

STUDY OBJECTIVES

To determine the current ingestants found in the multiply injured trauma patient and to determine if this select group of ingestants affected the resuscitation, evaluation, or convalescent management of these patients.

DESIGN

A one-year retrospective analysis was performed on all patients who were admitted to an urban trauma center with a discharge diagnosis of multiple trauma and who received a comprehensive toxicology screening test.

MAIN RESULTS

One hundred twenty-seven of the 177 patients (72%) who fulfilled the criteria had positive toxicology screens. Ethyl alcohol was the only drug present in 26 of these patients (20%); 57 (45%) were positive for drugs other than ethyl alcohol. A combination of ethyl alcohol and at least one other drug was quantified in 44 patients (35%). The most often encountered substances were ethyl alcohol (55%), marijuana (24%), and cocaine (21%). Twelve drug screens (9%) demonstrated pharmaceuticals (eg, acetylsalicylic acid, acetaminophen, or cyclic antidepressants) that may require specific antidotal treatment.

CONCLUSION

The ingestant profile found in this subgroup of trauma patients differed from those of previous studies. Although a select group of these ingestants requires specific treatment or affects the physical assessment of the patient, none of these trauma patients received more than supportive care.

The clinical value of drug analyses in deliberate self-poisoning

1. In a prospective, unselective study of self-poisoned patients in 1978 and 1987 blood samples for drug analyses were drawn on admission in 265 and 400 cases, respectively. 2. The results from the drug analyses were compared with the clinical information obtained on admission. The main drug taken was identified on admission in 228 (86%) in 1978 and in 383 cases (96%) in 1987 (P less than 0.001). 3. The clinical impression was completely in accordance with the results from the drug analyses in 192 cases (72%) in 1978 and 232 cases (58%) cases in 1987 (P less than 0.001). The discrepancies mainly involved secondary drugs. 4. There was no significant difference in the clinical course of the poisonings in situations where the correct main drug was identified on admission and where the wrong main drug was suspected. 5. Knowledge of the correct drugs used when admitted would not have prevented complications or deaths. 6. We conclude that extensive pharmacological drug analyses play a limited role in the routine management of patients admitted for deliberate self-poisoning.

Toxidrome recognition to improve efficiency of emergency urine drug screens

We correlated clinical symptom complexes of drugs (toxidromes) to results of 204 consecutive toxicological screens ordered in our emergency department. The toxidromes were divided into eight categories: sedative hypnotic, narcotic, stimulant, coma-apnea-seizure, hallucinogenic, anticholinergic, unknown, and "no drugs." Emergency medicine nurses, clinical pharmacists, and medical residents were asked to choose one or more of the above toxidromes independently when ordering the toxicology screen. The nurses achieved the highest symptom complex recognition of the drug (55 of 61, 88%) followed by medical residents (76 of 90, 84%) and clinical pharmacists (27 of 34, 79.4%), but the differences were not statistically significant. We conclude that the major determinant in selecting correct toxidromes is clinical experience of the practitioners. Given the percentages of toxidrome recognition, it should be possible to increase efficiency of laboratory use by ordering tests only for the drugs clinically suspected in a particular toxic patient.

Utilization and yield of drug screening in the emergency department

Emergency qualitative tests for drugs are commonly ordered during evaluation of cases of suspected drug overdose. We prospectively compared the utilization and yield of drug screens based on urine and of identical tests of gastric contents under actual clinical conditions in a busy metropolitan emergency department. During the 4.5-month study period, physicians ordered drug screening in 405 of 582 (70%) study cases. Screens of both types of body fluid were ordered in only 95 cases (16%), suggesting study physicians regarded these tests to be functionally equivalent. Drug screens of gastric fluid were favored in cases involving acute ingestion and in medically complicated cases requiring gastric lavage. Urine drug screens were favored in clinically stable cases with primarily thought or behavior disorders. In the 95 cases for which both drug screens were ordered, gastric screens in 18 cases detected 20 drugs not detected by urine drug screening. Urine screening, on the other hand, identified 74 drugs not found on gastric screening in 48 cases. Gastric drug screening also performed poorly in comparison to quantitative serum drug levels. Seventeen false-positive urine or gastric screens were noted as well. Despite significant technical limitations, physicians frequently order drug screens in our emergency department. Qualitative drug screening of gastric fluid may prove useful in cases involving acute ingestion, but samples of urine and serum must also be submitted for analysis if optimal test performance is to be achieved.

Obtundation in the elderly patient: presentation of a drug overdose

The case of an obtunded elderly woman is presented. The patient initially was thought to have suffered a cardiovascular accident but was discovered to have taken an overdose of flurazepam hydrochloride. Depression is a common and under-recognized problem in the geriatric population. As a consequence, suicide rates are highest in the elderly. Over- and underdosing of both prescription and nonprescription drugs are common means available to the suicidal elderly patient. These overdoses are often attributed to unintentional patient errors and overlooked for what they are, attempted suicides, or they are missed entirely as a cause of the patient's presentation. This case illustrates the need to consider drug overdose in the obtunded elderly patient.

Impact of drug screening in suspected overdose

We studied how emergency qualitative drug screens were ordered and used during the evaluation of 405 consecutive adult patients presenting to a metropolitan emergency department with suspected drug intoxication. Physicians completed a two-part questionnaire outlining diagnosis, diagnostic certainty, suspected drug(s), and management plans immediately following initial evaluation and again at the time of ED disposition. Screen results were reviewed prior to ED disposition in 361 (89%) cases. We found that qualitative drug screens were associated with substantial changes in diagnostic certainty, as measured by changes in probability estimates and changes in absolute mean log-likelihood ratios. In 196 cases for which all data were recorded prospectively, drug screens excluded a diagnosis of drug intoxication or specifically suspected drugs in 81 cases (41%), but identified previously unsuspected drugs in only 21 cases (11%, P less than .001). Management changes followed qualitative drug screen results in 16 of 361 cases overall (4.4%), but seven of these were also associated with diagnostic quantitative serum drug levels. Potentially critical interventions were begun in two cases following positive screens but delayed in another due to a falsely negative screen. Guidelines for more efficient test utilization are proposed.