Examining False Positive Results of the Methamphetamine Screening Test Kits by Using the Confirming Thin Layer Chromatography Methods at Chaiyaphum Hospital

Abstract

This retrospective descriptive research aimed to examine the false positive results from two different methamphetamine tests: the basic screening method and the confirming thin layer chromatography (TLC) method. Totally, 5689 urine screening results, using basic methamphetamine test kits, of the suspected users during the 2016-17 fiscal years were purposively collected from police stations and other organizations in Chaiyaphum Province. The confirming TLC results of the suspected were later gathered from Chaiyaphum Hospital. The data collection table including  two main sections of general information and positive methamphetamine results was employed to systematically record information.  Collected data were analysed by using descriptive statistics: number and percentage. 

Findings illustrated that in the 2016 fiscal year, 2883 of 3428 methamphetamine results (84.10%) were true positive whereas 545 cases (15.90%) showed false positive results after confirming the results by TLC method. In the 2017 fiscal year, 2002 of 2261 methamphetamine results (88.54%) were true positive while 259 cases (11.46%) showed false positive results after confirming the results by TLC method.

This study confirms that although preliminary methamphetamine screening test kits could separate the methamphetamine users from non-users, such method could offer the false positive results. The confirming TLC method is recommended to protect the methamphetamine -like derivative consumers from the false penalties.  This study also suggests the confirming TLC results should be required as a substantial evidence for the Thai Criminal Court. Further research is needed to examine the sensitivity and specificity of the basic methamphetamine screening test. Demographical data of the suspected samples including occupations and education should also be recorded for further investigation.