Interference with Testing for Lysergic Acid Diethylamide (Drug Monitoring and Toxicology‪)‬

Testing for drugs of abuse (DOA) is an important diagnostic tool that may contribute to the establishment of the diagnosis in the intoxicated patient. [3] Several types of DOA tests have been used in the clinical laboratory, such as chromatographic methods and antibody-based assays. More recently, immunoassays have become a popular tool because they are easy to perform and guarantee short turnaround times. Unfortunately, immunoassays are associated with such caveats as lack of sensitivity or lack of specificity [1]. Results that are positive by immunoassay may be confirmed by more complicated and time-consuming techniques such as thin-layer chromatography or gas chromatography-mass spectrometry (GC-MS). Frequently, clinical decisions have to be made before preliminary results by immunoassay can be confirmed by another method. Therefore, the interpretation of test results requires the knowledge of substances that may interfere with the testing [1]. We have evaluated the new homogenous Emit immunoassay for lysergic acid diethylamide (LSD) from Behring Diagnostics. The assay was associated with a high false-positive rate when we tested urine samples that were submitted by patients from our hospital population. Further investigation revealed that certain prescribed medications interfered with the LSD Emit test in vitro, but not with Emit tests for other DOA. Materials and Methods