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Fundamentals of Toxicology Testing

Toxicology screening plays a vital role in diagnosing and treating patients who exhibit symptoms potentially caused by drug exposure. This includes cases of unintentional poisoning, self-harm attempts, or environmental exposures. Such patients commonly seek medical attention in the emergency department and necessitate specialized diagnostic testing for proper evaluation and care.


This page primarily caters to screening needs of acutely ill patients, rather than workplace drug tests or routine testing conducted in rehabilitation programs. By narrowing its scope, it ensures focused attention on the targeted audience.


The availability, accuracy, and utility of toxicology screening tests for exposures and drug abuse can vary. It is crucial to understand the limitations and clinical applicability of these tests to ensure proper ordering and interpretation of the results.


A substantial proportion of visits to medical providers for acute care are linked to reported drug exposures. Historically, alcohol intoxication has been the primary cause of substance-related patient visits, and it continues to hold that position. However, there has been a noticeable increase in visits related to opioids, cocaine, marijuana, and synthetic drugs over the past three decades. This highlights the evolving landscape of substance-related healthcare encounters.


This comprehensive guide outlines the necessary procedures and specimen requirements for urine and serum testing. In cases of acute illness, serum and urine samples are collected for laboratory testing without specific consideration for drug screening. Ideally, a urine specimen should be obtained within four minutes of providing a sample and have a volume of at least 30 mL. The urine temperature should fall between 32.2°C (90°F) and 37.7°C (100°F), with a pH level ranging from 3.5 to 11.5. These requirements ensure that the sample accurately represents the individual providing it, without any added diluents or substances that could potentially interfere with testing.


Over the years, there have been significant advancements in toxicology screens. Modern methods such as enzyme-linked sorbent immunoassay (ELISA) and cloned enzyme donor immunoassay (CEDIA) have replaced older techniques like gas chromatography and radioimmunoassays. The shift towards these newer methods can be attributed to their speed and ease of use. On the other hand, comprehensive drug screens using alternative methods are often expensive and time-consuming, taking weeks to yield results. Consequently, these approaches are impractical for clinical use.


Drug testing can be conducted using various samples, such as urine, serum, breath, sweat, or saliva. Breath testing is primarily employed for estimating alcohol levels, while urine and serum tests remain the most frequently used methods by medical professionals. Urine testing is commonly employed for screening illicit drugs of abuse. In the United States, five drugs - cocaine, amphetamines, marijuana, phencyclidine (PCP), and opioids - are routinely screened for in urine tests.


Toxicology screening is an indispensable diagnostic tool in acute care settings, aiding healthcare providers in identifying drug exposures and eliminating alternative causes of illness. Properly interpreting test results necessitates a comprehensive grasp of its constraints and relevance.

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