Between 1998 and 2000, a surprisingly high number of positive results was noticed in our regional medium secure unit when testing for D-lysergic acid diethylamide (LSD). This led to an investigation of possible factors involved. It was felt that the testing protocol, particularly the use of a single, non-isotopic homogeneous immunoassay without routine further confirmatory testing, was largely to blame for what seemed to be a high incidence of false positives. On two different occasions, samples from each patient were sent, on the same day, to two different laboratories. At the first laboratory, only one test method was used and at the second one test plus two confirmatory tests were carried out.
Out of a total of 23 patients tested on two separate occasions, the first laboratory gave three positive results the first time and three positive results the second, while the second laboratory gave only one positive result on the second occasion that samples were sent and none on the first. This reinforces the belief that, without adequate confirmatory analysis, many psychiatric and non-psychiatric prescribed drugs can give false positives.
Positive LSD results should be confirmed by at least one, preferably chromatographic, alternative method. A protocol for testing and reporting LSD in psychiatric patients should be considered in order to minimise the risk of obtaining false-positive results which have negative clinical, legal and psychological repercussions.
Email your librarian or administrator to recommend adding this journal to your organisation's collection.