Abstract
Background: The current study was conducted to compare ELISA with thin layer chromatography (TLC) methods for diagnosis of morphine in the urine. Methods: Positive urine samples for morphine confirmed by immunochromatographic strips were collected from the Imam Reza Toxicology Laboratory, Mashhad University of Medical Sciences, Mashhad, Iran in 2012 for the current study. Then, the collated urine samples (70) were analyzed by both ELISA and TLC methods. Results: On analyzing samples by TLC, 57 out of 70 (81.4%) revealed morphine spot, whereas by ELISA method all samples were positive. The difference was statisticaly significant (P=0.0001). Both immunoassays had the same 100% positive results. The possible 18.6% false positive results might be due to drug interactions. TLC is more specific but time-consuming and less sensitive than ELISA is. However, TLC is an old method but more reliable than ELISA. Conclusion: Contrary to the claim that commercially available ELISA kits have a high specificity for detection of morphine derivatives; it seems that false positive results may occur. It is thus recommended that all positive results obtained from ELISA be checked by a cheap widely available confirmation test of TLC or ideally by a quantitative technique such as GCMass spectroscopy, particularly for legal purposes.
Highlights
Drug abuse is a critical problem throughout the world
In this study, we aimed to evaluate the reliability of data obtained from a morphine ELISA kit versus a cheap available confirmatory analytical method named thin layer chromatography (TLC)
A total of 70 urine specimens from drug abusers of Mashhad which had positive results confirmed by membrane based immunochromatography assay for morphine derivatives in the Imam Reza
Summary
Drug abuse is a critical problem throughout the world. Urine drug screens (UDS) are a frequent practice applied to detect common drugs of abuse. UDS are generally done using immunoassay methods [2] These assays for drugs of abuse are well-established [3,4,5,6]. Immunoassay UDS use specific antibodies against current drugs of abuse or their metabolites to detect them. Results: On analyzing samples by TLC, 57 out of 70 (81.4%) revealed morphine spot, whereas by ELISA method all samples were positive. Conclusion: Contrary to the claim that commercially available ELISA kits have a high specificity for detection of morphine derivatives; it seems that false positive results may occur. It is recommended that all positive results obtained from ELISA be checked by a cheap widely available confirmation test of TLC or ideally by a quantitative technique such as GCMass spectroscopy, for legal purposes.
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