Additionally, GC-MS quantifies the amount of drug present in a sample. This test is more specific than immunoassay testing, as it detects drugs by molecular structure. Gas chromatography/mass spectrometry (GC-MS) is the gold standard for confirmatory testing. Confirmatory tests are more timely and costly and are performed by highly trained laboratory personnel. 2 The decision to perform a confirmatory test should take into consideration the patient’s history, clinical judgement, and the potential impact on patient care. For this reason, immunoassay testing should be considered preliminary and presumptive.Ĭonfirmatory testing should be considered following a presumptive positive screening test. However, antibodies may detect drug metabolites with similar structure and characteristcis, leading to false-positive results. Immunoassay technology uses antibodies to detect drug metabolites. The 3 most common types of immunoassay testing include enzyme-multipled immunoassay technique, enzyme-linked immunosorbent assay (ELISA), and fluorescence polarization immunoassay. Results are relatively rapid, and the test can screen for a wide variety of drug metabolites. Immunoassay testing can be performed in a laboratory or in an office using point of care testing. 2 Immunoassay testing is primarily used for initial screening. There are 2 main methods for urine drug testing, screening and confirmatory. Certain medications, foods, and disease states may cause valid outliers however, a pH 11 or a specific gravity 1.030 increases the suspicion for adulteration. The temperature of urine should be between 90 to 100 degrees Fahrenheit measured within 4 minutes of collection the pH should be consistent with the range of 4.5 to 8 the specific gravity should be between 1.002 and 1.030 and the creatinine should be greater than 20 mg/dL. 2 These factors should be considered when evaluating results to rule out adulterated samples. When collecting a urine sample, several factors should be recorded to ensure accurate collection and avoid false-negative results, including temperature, pH, specific gravity, and creatinine. Both parent and metabolite compounds can be detected in the urine. Additionally, drugs can be detected in the urine for a longer duration compared to blood or serum, and the concentration is typically higher. Urine is most commonly used due to its ease of collection. Drug testing can be performed using various biologic specimens, including urine, saliva, hair, sweat, nails, meconium, and blood. Drug tests are also performed in the workplace to identify illicit substance abuse. 1,2 Drug testing is frequently used in clinical setings to identify substance-use disorders, confirm medication adherence, or identify overdoses. population over 12 years of age reporting illicit drug use in 2018, an increase from 7.9% in 2004. Abuse and misuse of prescription and illicit drugs is a growing concern, with 11.7% of the U.S.
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