Interference with testing for lysergic acid diethylamide
Detlef Ritter, Cherise M Cortese, Linda C Edwards, Judith L Barr, Hyung D Chung, Christopher Long
Clinical Chemistry April 1, 1997 Peer reviewed DOI: 10.1093/clinchem/43.4.635
Summary
A high rate of 4.2% positive results for LSD was found in urine samples from psychiatric patients, but these results were not confirmed by more accurate tests. Samples that tested positive for LSD with the Emit assay showed negative results with two radioimmunoassays (RIAs) and gas chromatography-mass spectrometry. The positive Emit results were influenced by therapeutic medications, which specifically interfered with the LSD assay but did not affect other drug tests.
Study at a glance
| Sample size | 1,898 |
|---|---|
| Population | urine samples primarily from psychiatric patients |
| Key finding | The Emit assay produced false positive results for LSD in urine samples due to interference from therapeutic medications. |
Abstract
Abstract We found a high rate (4.2%) of positive results for lysergic acid diethylamide (LSD) by Emit in 1898 urine samples that were submitted primarily from psychiatric patients for drugs-of-abuse (DOA) testing. Specimens that tested positive for LSD by Emit subsequently tested negative for LSD with two RIAs. Furthermore, LSD was not detected in randomly selected Emit-positive urine samples by gas chromatography–mass spectrometry. Normal urine samples tested positive for LSD by Emit when they were supplemented with therapeutic medications that were prescribed for patients with positive urine LSD results by Emit. These therapeutic drugs interfered specifically with the Emit assay for LSD, since other Emit DOA tests were not affected by these medications at the tested concentrations.